300Tdi Rear Main Oil leak.

[BlueRunning]

Mods please let me know if this should go in a different thread...

Hi all,

The other day I was driving my Disco 1 300tdi (435k kms, owned for 15+yrs) to Uni for my graduation, and upon getting out of the car saw a lovely rainbow trail following my exact route. I thought this to be a bit odd, but as it was ****ing down with rain and I was late, dismissed it for later. Later came around and I had a look under on startup - couldn't see anything dripping, so I thought it must have been another car. Cut to two days later, I drove to work in the rain, and again, rainbow trail... End of the day comes around and I check the dipstick - no oil, like zero oil on the dipstick. I thought this may have been due to the heavy tilt angle of where I was parked, but I added my 1L of top-up oil and gingerly made my way home. Upon having a look under the beast, I saw that there's a non-zero flow of oil emanating from the drain hole at the bottom of the bell-housing, suggesting to me a failure of the rear-main oil seal. Note that the oil pressure light never once came on or even flickered (I know the light works at least since it comes on when in pre-start key position).


Now, at around the beginning of this year/end of last (roughly 10 - 20k kms ago), my old transmission (auto) finally gave up its ability to shift between 1st and 2nd, and so I popped it out and popped a new 2nd hand one back in. While I was there, I thought I'd change the rear main oil seal for good measure as its a pain in the backside to access, and my dad and I thought it was weeping a tad bit so could use an early replacement. During this process, from memory we had differing opinions on best way to install, and had some serious faff issues trying to get the dog on. Eventually we were successful but a bit confused as we thought it should be a relatively straightforward swap (based on what we watched/heard). Either way, no significant oil leaks presented themselves for a solid one or two runs of oil (changed every 10k kms).

Cut forward to the start of winter, the beast began its standard cold start up routine of not wanting to go until a few turn-overs (nothing unusual as glow plugs are a long-time dead), however I did notice the car develop a noticeably more intense in-cabin vibration when cold and idling (worse in gear when revs slightly drop at idle). I thought this was possibly just the idle screw had slightly moved over time and was now idling a tad too low, however since the taco was in its usual idling spot and I am kinda lazy, I didn't think much about and drove on. The car runs stellar when driving and the vibration mellows wayyy out when warm.

Cut forward again to the start of July, the day before I was leaving for my Euro holiday I noticed a small pool of oil beneath the car after moving out of the backyard (was doing some tinkering with windows). I thought this strange, since I've never noticed this before despite it being parked there many times for the odd jobs. When I came back again, I looked around the engine bay and saw the brake vacuum pump had considerable oil beneath it and a lovely oil pool in on the top of the diff, so I thought that it must be slowly leaking from there and said pool must have drained out when I drove up into my driveway (which is slightly inclined). I switched out the gaskets on the vacuum pump, no worries. When I was under there and poking around, I saw oil on the bell-housing, but didn't think much of it since that's seems to be common run-off point for oil that's been blow off the engine (there's a few tiny leaks here and there). I didn't notice any major pool of oil, and when it was raining in the weeks before last I certainly didn't notice the very obvious rainbow splotches.

Now I'm not saying that just because I didn't notice any these things they weren't happening, I likely was just not paying too much attention to that area as I just friggin replaced that seal.

Cut to now, I'm under the car, oil is drip drip dripping out of the drain hole and its almost certainly coming from the rear main seal. Now, as far as I know, there are only 3 things this could be and I'll list them in order of pain in the bum:
1. Crank case pressure too high (sometin is blocked)
2. Rear main seal is cooked (why now after 20k kms)
3. Crank shaft is wibbly wobbly and engine needs rebuild (which might explain the undue low-rev vibrations)


I would appreciate any input from you engine/300tdi/disco1 aficionados on what might be causing this, and any potential things I could do BEFORE I yank the engine out and rebuild the darn thing.

Many Thanks.

[workingonit]

I thought I'd change the rear main oil seal for good measure



I assume the seal was white plastic (teflon?) in an aluminium frame. Did you lube the seal or install dry? The seal should be installed dry, and that includes removing any oil on the shaft. Friction warms the plastic causing it to tighten further around the shaft.

[Blknight.aus]

run a compression and leakdown test.

Ive got a work run coming up past and through sydneyish in the next 4 weeks or so. If youd like a hand drop me a DM.

[BlueRunning]

I assume the seal was white plastic (teflon?) in an aluminium frame. Did you lube the seal or install dry? The seal should be installed dry, and that includes removing any oil on the shaft. Friction warms the plastic causing it to tighten further around the shaft.

Yes from memory it was indeed a while plastic/teflon and we installed it dry. I think my dad and I had differing opinions on whether the inner piece should pop out of the seal or not as we couldn't manage to do that. He was the one driving the ship that day and I don't remember exactly what happened cuz we were quite cooked by then after working on the auto trans for hours.

[BlueRunning]

run a compression and leakdown test.

Ive got a work run coming up past and through sydneyish in the next 4 weeks or so. If youd like a hand drop me a DM.

Mate that is very generous of you. I'll investigate the process behind running a comp and a leakdown test and dm you if I need help. I know poor compression and sealing is bad but not sure how that translates to determining if the crank itself is wearing...

[Blknight.aus]

Mate that is very generous of you. I'll investigate the process behind running a comp and a leakdown test and dm you if I need help. I know poor compression and sealing is bad but not sure how that translates to determining if the crank itself is wearing...

compression test and leak down test is to help with the rough running while cold and idling, if youve got a cylinder being lazy it'll usually have low compression and a leak that wont pass muster.

it also means you're pulling the glow plugs and that can show you if a cylinder is being miss fed by the soot or oily residue on the plug

[AK83]

.....

Cut to now, I'm under the car, oil is drip drip dripping out of the drain hole and its almost certainly coming from the rear main seal. Now, as far as I know, there are only 3 things this could be and I'll list them in order of pain in the bum:
1. Crank case pressure too high (sometin is blocked)
2. Rear main seal is cooked (why now after 20k kms)
3. Crank shaft is wibbly wobbly and engine needs rebuild (which might explain the undue low-rev vibrations)


I would appreciate any input from you engine/300tdi/disco1 aficionados on what might be causing this, and any potential things I could do BEFORE I yank the engine out and rebuild the darn thing.

Many Thanks.

As I understand it, it's not necessarily the seal that's leaking, ie.the seal around the crank.
It's very likely to be the aluminium housing part of the seal. It's very thin along the bottom edge and can warp with even a small amount of time.

Did you use a gasket between the rear main seal and block, or did you use sealant?

Watch these two videos from Brittanica Restoration about 300tdi rear main seals.

first one will show how he uses sealant watch it carefully as he shows the slight gap between along the lower edge of the housing, ie. it's not dead straight.

https://youtu.be/y-gg8XYhCLY'si=-Yj9hsG6VOa_BnaM

Second video shows how he uses a slightly different rear main seal with two small bolt holes for the HS2.8lt engine, and drills and taps the block for fitting two small bolts to secure the bottom edge better, so that the aluminium housing doesn't warp(he does that in another video tho)

https://youtu.be/xchNzSd8RKE'si=9KNsO9-pd1cH6KLJ

[BlueRunning]

compression test and leak down test is to help with the rough running while cold and idling, if youve got a cylinder being lazy it'll usually have low compression and a leak that wont pass muster.

It also means you're pulling the glow plugs and that can show you if a cylinder is being miss fed by the soot or oily residue on the plug

I'll have a look at the condition of the glowplugs when I pull them out, but I know for a fact that the tips of at least one of my injectors was extremely sooty. The copper crusher washer on injector 3 (3rd injector in from the front) had failed and oil and diesel was making its way up and out. When I replaced it the injector shaft was v oily and the tip was coated in black soot. Didn't think much of it at the time and chucked it back in with a new washer (doesn't leak now).

I also didn't think of this but my rocker cover seal is chronically leaking despite a relatively new gasket and re-application of high-temp RTV on 3 different occasions. I have a new seal ready to install but perhaps the leak is more so due to excessive top-end pressure... I've done the ole' oil cap test and it doesn't seem to be bouncing around too much but don't have a good reference for what its actually supposed to look like for a mint engine.

[Blknight.aus]

I'll have a look at the condition of the glowplugs when I pull them out, but I know for a fact that the tips of at least one of my injectors was extremely sooty. The copper crusher washer on injector 3 (3rd injector in from the front) had failed and oil and diesel was making its way up and out. When I replaced it the injector shaft was v oily and the tip was coated in black soot. Didn't think much of it at the time and chucked it back in with a new washer (doesn't leak now).

I also didn't think of this but my rocker cover seal is chronically leaking despite a relatively new gasket and re-application of high-temp RTV on 3 different occasions. I have a new seal ready to install but perhaps the leak is more so due to excessive top-end pressure... I've done the ole' oil cap test and it doesn't seem to be bouncing around too much but don't have a good reference for what its actually supposed to look like for a mint engine.

Remove and service the oil seperator for the crank cae ventilation system and check that the hose that runs round the back isnt crushed.

as has been metioned earlier the rear leak is not likely to be the seal at this short an interval but the casing of the seal. if you dont press it home evenly and carefully it will warp.

i very much doubt crank "wibble" is the cause of the issue, if it was it'd be out of bed and youd have draught holes in the block by now.

[AK83]

....

I also didn't think of this but my rocker cover seal is chronically leaking despite a relatively new gasket and re-application of high-temp RTV on 3 different occasions. .....

LOL! aren't they all!
I used to get that too. Make sure you always get new inserts for the three cover nuts. With new seal and new inserts, make sure both cover and head mating surfaces are clean, no old rubbery gasket residue on either side. Brake cleaner is good for that.
Only do the three cover nuts up to 10Nm too, not more. More makes the seal leak for some reason.
I could never get a socket(hence a torque wrench) onto the rear nut, so 10Nm is guesswork with a short handle spanner, it's easy to overdo it.

I reckon I've done maybe 7 or 8 tappet adjustments. if I reused the seal and fixing inserts, for sure it'd leak. New gasket and used inserts, it'd leak a bit later. all new bits, never leaked between oil changes and/or tappet adjustment.
RAVE says that the cover gasket can be reused up to 5 times. My experience is new every time if you don't want it leaking.

I think I'm currently on 20K klms since I last adjusted tappets(they're not noisy), and still not leaking. There is a misty residue build up, but that usually comes from the cyclone mating surface at the cover. I tried gooping that up with RTV type stuff and doesnt' leak any more, just the long term misty build up.

Like blknight said, also check the hoses that go too the cyclone. Hoses get hard, stupid expensive for their size, I found cheaper silicon hoses. Once hard they leak no mater how hard you tighten the clamps up.

ps. I thought that maybe the plastic cyclone may be deforming over time with heat/cold cycles ... so I got an Allisport aluminium one. Still leaked, so that was a 'waste of money' in a sense. Looks nice, but I'm not really that way inclined. I think plastic one may be fine, rubber oring is useless, a smear of rtv may be helpful there.

[BlueRunning]

Remove and service the oil seperator for the crank cae ventilation system and check that the hose that runs round the back isnt crushed.

as has been metioned earlier the rear leak is not likely to be the seal at this short an interval but the casing of the seal. if you dont press it home evenly and carefully it will warp.

i very much doubt crank "wibble" is the cause of the issue, if it was it'd be out of bed and youd have draught holes in the block by now.

Finally found some time to start digging around today. Started with topping oil up and then pulled off the cyclone filter. The hose between itself and the intake seem fine to me, no blockages or crushing as I can blow through it fine and dandy.

The cyclone itself seems fine but I'm not really all to sure what the service method is for these since you can't dissemble it. Don't really have any kero on hand or anything of the sort so instead I just started the ole girl with it removed and all its hoses disconnected.

Safe to say the confusion continues from here. It's been sitting for roughly 2 weeks now without being run so any oil that was in it was well and truly out. I fired her up and let the engine idle until the gauge said warm (roughly 10/15mins). Checked the undercarriage constantly though out this - no oil.

Right as the gauge was reaching halfway (wasn't staring at it the whole time so might have already been sitting there for few mins, but don't think so), I turned the car off and decided to see what would happen if I reconnected the whole cyclone apparatus.


Reassembled and installed, turned the car and literally within less than a minute (was the time it took me to put something in the bin and then check under the car) there was the accursed dripping from the bell housing. I took note of the flow (but not a video like a fool) and decided to run it again with the cyclone off again.

Did this, ran it and unfortunately still leaking, but not nearly as much??? Not sure if this was because of it actually leaking or vibrations shaking the oil sitting in there still or what.

A few things I did notice is that

a) the crankcase hose has zero noticeable pressure. Plugged my finger over it and didn't feel a pull or push.
b) the breather hose going to the intake also had zero pressure. Again plugged my finger over it and no noticeable suck even when I revved the motor right up
c) the rocker cover outlet has good positive pressure. Doesn't seem excessive to me and didn't blow out any oil or an overly noticeable amount of smoky air when revved up.
d) when blowing into the rocker cover air inlet on the cyclone, air easily came out of both the intake and crank case outlets. The same could be said when blowing into the either of those as well.


I'm not sure what to make of all this, but I did read that the cyclone is supposed to have a one way valve somewhere. Is it possible that this has failed and the air from the rocker cover is heading straight down into the crank causing high pressure?

Planning on doing the comp and leak test tomorrow arvo. Let me know what you guys think.

[BlueRunning]

Update - The plot thickens...

Tested yesterdays theory and ran engine until warm and then some to see if no cyclone = no leak (unlikely but thought i'd check) - the leak occurred about ~10min into running, just as the gauge arm began to tick up towards standard running temps.

As this dashed my (albeit small) hopes of just replacing the cyclone filter and calling it another job well done, I heated the engine up a bit longer and pulled the glowplugs from cylinders 2, 3 and 4. I left cylinder 1 in because the bloody AC compressor sits directly in front of it and I couldn't be fked to remove that entire apparatus. Some things I noted about the plugs:
- All plugs came out nice and easy, barely any force required to remove them (engine was warm so go figure)
- Plugs 3 and 4 looked nice and shiny down their shaft, although a bit of carbon build up on the tips.
- Plug 2 was absolutely cooked and needed pliers to pull out. Was absolutely caked in thick carbon, which had gammed up the entire bore in which the plug sits.

I then disconnected the fuel line and ran what I believe was two sets of dry tests (as I didn't add any additional oil to the bores through the plugs before conducting testing), my results were as follows:

Cylinder 2: T1 = ~325psi, T2 = ~310 psi
Cylinder 3: T1 = ~350 psi, T2 = ~340 psi
Cylinder 4: T1 = ~350 psi, T2 = ~340 psi

It seems clear to me that cylinder 2 is somewhat of a problem child in this engine, although since I haven't tested cylinder 1 I don't know if it has a partner in crime or not. Despite cylinder 2's crimes against the environment (in the form of unnecessary soot), the variance between these is less than 10%, which I heard is a good metric for telling if a cylinder has sht the bed or not. These values also apparently align with the manual's recommended values of 360 psi (I don't have the book so can't verify this).

Based on the above, it appears that despite me flogging the ole girl up and down the coast for the past 5 years, and my dad for the 10+ years before me, the OG cylinders are still holding their own (we don't actually flog it, revs stay below 3000 always).


In addition to the above, I found some VERY interesting relationships between engine RPM (when in neutral) and the leak flow rate. When idling at cold temps there are no leaks, however when idling at warm temps there is a drop every 3 seconds or so. I thought it would be interesting to see how much this leak increases when I rev the engine up, so i did so and had a geez - the leaks stopped... When the revs hit around 1500RPM and higher, the leaks cease to exist. What is even more interesting is that when I back off the revs to idle, a small but constant stream of oil emanates from breather hole for about 10 seconds, before the flow rate returns to its standard drop-per-3-seconds rate.

This just goes to show I have absolutely zero idea what is going on inside of this engine, because this make absolutely no sense to me. What on earth could be going on here? Is it just that the engine is cycling through enough oil when at high rpm that oil isn't bathing the rear of the crank, and then when you drop off the revs it dumps all this excess oil it now doesn't need, which then creates a temporarily increased leakage rate???

Let me know what you guys think!

[Blknight.aus]

your rings have lost tension

really loosly (pun may or may not be intended)

at low RPMS and load the cylinder pressure spike isnt abrupt and the slow stroke of the piston gives enough time for leakage to occur. Once the revs come up the pressure rises faster and the pistons moving faster so the pressure spike itself seals the gap by putting more pressure on the rings and helping sealing by acting like a fluid barrier (same sort of principle as an air curtain door keeps AC in and hot air out) and theres less time on the stroke to let the air escape.

and if the crank case vent is doing its job properly it scavanges the vapor out of the cylinder head but not the crank case. at idle theres not enough airflow through the intake trunk to get that scavaging working properly so the crank case pressure can be higher.

[BlueRunning]

your rings have lost tension

really loosly (pun may or may not be intended)

at low RPMS and load the cylinder pressure spike isnt abrupt and the slow stroke of the piston gives enough time for leakage to occur. Once the revs come up the pressure rises faster and the pistons moving faster so the pressure spike itself seals the gap by putting more pressure on the rings and helping sealing by acting like a fluid barrier (same sort of principle as an air curtain door keeps AC in and hot air out) and theres less time on the stroke to let the air escape.

and if the crank case vent is doing its job properly it scavanges the vapor out of the cylinder head but not the crank case. at idle theres not enough airflow through the intake trunk to get that scavaging working properly so the crank case pressure can be higher.


Ok I think I understand the problem you are outlining. Perhaps the rings on cylinder 2 have been semi perma-compressed by the carbon buildup in that cylinder, or perhaps it's just from old age.

What I don't understand is how this problem would result in the observed sudden increase in oil flow rate, to be followed by a decrease in flow to a steady, slow rate?

Is the fix for this problem a full rebuild of the pistons (new rings, rebore, etc?) or could I get away with an easier fix.

In the meantime as well, would it be viable to install a small vacuum motor to relieve crank pressure? I may instead just do a quick botch job and install a catch can at the bottom of the bell housing so I can at least stop the oil loss.

Cheers

[Blknight.aus]

if its a ring sticking from carbon build up you can try putting a flushing agent in then giving it an italian tune before dumping the oil.

if its rings and that doesnt work the only proper fix is a rework of the bores and pistons.

putting a vac pump on the engines probably not going to be great for the vac pump.

good luck

[BlueRunning]

if its a ring sticking from carbon build up you can try putting a flushing agent in then giving it an italian tune before dumping the oil.

if its rings and that doesnt work the only proper fix is a rework of the bores and pistons.

putting a vac pump on the engines probably not going to be great for the vac pump.

good luck


Ok ok,

I actually have access to a borescope which can take photos and provide a live feed, so I'm gonna pop that into the cylinders as well and have geez at the condition of the bores and pistons. Will post photos here after.

Do you have a recommended flushing agent for this? I was looking around and found a product called BG EPR which acclaims that you can add it without having to worry about lubrication impacts or draining the oil??

Looking forward to doing this Italian tune as well lol

Cheers.

[TonyC]

I've never used it, but people on have said good things about it.

Engine Blowby Kit - Cost Effective Maintenance (https://costeffective.com.au/product/engine-blowby-kit/)

Tony

[Blknight.aus]

Ok ok,

I actually have access to a borescope which can take photos and provide a live feed, so I'm gonna pop that into the cylinders as well and have geez at the condition of the bores and pistons. Will post photos here after.

Do you have a recommended flushing agent for this? I was looking around and found a product called BG EPR which acclaims that you can add it without having to worry about lubrication impacts or draining the oil??

Looking forward to doing this Italian tune as well lol

Cheers.


Theres a lot out there, I generally use the supercheap one, the nulon one or whatever the customer provides for me because its the flavor of snake oil marketing they like best.

There are some that you must dump, there are some you dont and there are some that are a 3 bottle package.

1 you add before an oil change, the next is an oil stabilizer additive and the last is a seal saver that you only use if the seals are still leaking once youve run the second bottle for a few hours.

[BlueRunning]

Theres a lot out there, I generally use the supercheap one, the nulon one or whatever the customer provides for me because its the flavor of snake oil marketing they like best.

There are some that you must dump, there are some you dont and there are some that are a 3 bottle package.

1 you add before an oil change, the next is an oil stabilizer additive and the last is a seal saver that you only use if the seals are still leaking once youve run the second bottle for a few hours.

Haven't had time to flush engine yet, probably will have a peek around with the borescope tonight then run it hard and see if there's a difference.

Do you have any suggestions for what I should be looking for in the cylinders to indicate health status? (I.e. shiny, dull, cross hatching, etc?)

Also, I'm thinking that it might be a viable idea to open up the little cover plate on the front side of the bell housing-engine interface (the one used to connect the flywheel and flex plate) and see if I can have a look at the rear main seal. If it's clearly leaking out of the seal-crank interface, would that suggest high pressure blowout, but if it's leaking from the aluminium frame-engine interface, perhaps the seal is just warped?

Cheers.

[Blknight.aus]

dull metal with a cross hatch is good.

anything else is less optimal.

[loanrangie]

I'll add my 2c worth, i vaguely remember something about the 300tdi rear main seals where the bolt holes aren't centered correctly and need to be drilled out slightly for the seal to center itself on the shaft .
Possibly it was Justin Cooper that mentioned this ?

[BlueRunning]

I'll add my 2c worth, i vaguely remember something about the 300tdi rear main seals where the bolt holes aren't centered correctly and need to be drilled out slightly for the seal to center itself on the shaft .
Possibly it was Justin Cooper that mentioned this ?

Interesting, however I don't see how this would only develop after 20k kms on the new seal, although you never know with Land Rovers.

I have devised a new method of oil capture for the time being, however she's leaking a bit more than I anticipated and overflowed the catch can (330ml) in one day, only 50kms of city driving done. I reckon it lost more like 500ml as well which means 100ml per 10km in the city. Not good at all.

[BlueRunning]

dull metal with a cross hatch is good.

anything else is less optimal.

Endoscope was a few mm too big to fit unfortunately. Still performed sludge flush and the Italian tune. Dumping and changing oil tonight and will do a test drive to see if she's still leaking. I'm not too hopeful this has actually fixed the problem but we will see. In the case it hasn't, my understanding is that the oil is essentially being pushed out of the seal by the excessive pressure in the crankcase which has blown by the cylinder rings. With that in mind, would this pressure therefore be alleviated if you removed the oil dipstick? (Considering it goes right into the sump and therefore the area which is excessively pressurised).

If so, in the case that the engine is still leaking oil, if I remove the dipstick and the oil leak persists, does this then indicate that the problem is in fact not crankcase pressure and instead just a catastrophic failure of the rear main seal?

Cheers.

[Blknight.aus]

Endoscope was a few mm too big to fit unfortunately. Still performed sludge flush and the Italian tune. Dumping and changing oil tonight and will do a test drive to see if she's still leaking. I'm not too hopeful this has actually fixed the problem but we will see. In the case it hasn't, my understanding is that the oil is essentially being pushed out of the seal by the excessive pressure in the crankcase which has blown by the cylinder rings. With that in mind, would this pressure therefore be alleviated if you removed the oil dipstick? (Considering it goes right into the sump and therefore the area which is excessively pressurised).

If so, in the case that the engine is still leaking oil, if I remove the dipstick and the oil leak persists, does this then indicate that the problem is in fact not crankcase pressure and instead just a catastrophic failure of the rear main seal?

Cheers.

the theory is sound.

I would also make the effort of disconnecting the feed tube down from the oil sperator on the side of the engine. and running the engine with that disconnected. (and vented off elsewhere.)