Rebuilding my 300Tdi

[Shonky]

This month, my Defender and I will click over 12 years together. In that time, we have moved house no fewer than 14 times, travelled much of eastern Australia, had two iterations of camping fit-out, failed to proceed only once (my fault - check your swivel oils, people) and travelled just over 200,000kms.

For the most part, it has been a trouble-free daily driver and adventure machine. We'll gloss over the constant and intensive maintenance that makes that possible and consider it part of the experience.

There's no denying, however, that the old bus is showing her age these days. It still presents well - I keep it tidy - but the last convoy to Tassie saw me relegated to tail-end-Charlie so as my companions could see where they were going and avoid smoke inhalation. Sometime after returning home, a stern letter from the EPA rubbed salt into the wound. Unsurprisingly, there has been an inverse correlation with the amount of smoke produced and the amount of power produced. It could probably pull the skin off a rice-pudding, but only a small one.

To put it simply, after 375,748kms across three owners over 27 years and 10 months of life, it needs some love.



It is worth noting that there are other intercurrent issues (cracked exhaust manifold, for example) which are heavily contributing to the problem, but various trustworthy sources suggest that the big-end bearings are likely at end of life by now anyway, and I am at a brief juncture of my life where the Venn-diagram of space/time/money has converged temporarily and given me a window to do this myself.

Additionally, when I replaced the head in 2016 I learned a few lessons the hard way:
Firstly, if you're removing the head; don't forget the coolant drain plug on the left side of the block otherwise you'll dump a bunch of coolant into your decapitated engine when you lift the head off.
Secondly, if this happens, no amount of paper towels will get all the coolant out of the bores and the remnants will settle around the rings and after 3 weeks of sitting, will have corroded spots on the cylinder walls. If I had my time again, a good dousing with WD40 to displace the moisture would have probably been an idea...



Is this significant? I don't know. But I've always wondered if this might be a factor, despite my best efforts at cleaning up the surface corrosion on the bores and the lack of any acute changes after this event. This will give me an opportunity to resolve it and stop wondering.

So, the time is now.

I thought I'd keep a bit of a thread going as I progress, as it may help someone else down the line and I'm sure I'll be needing some advice from the brains trust as we go.

I like to think I'm a little more savvy than 6 years ago when I last had the head off, and indeed at that time I was more-so than 6 years prior to that when I bought it. There's still much to learn though and I think it is worth adding the disclaimer that I am no expert, and that I haven't rebuilt an engine before. This is not a "how-to". Replicate my inevitable mistakes at your peril.

[Shonky]

Enough waxing lyrical.

So, the engine is down on power and blowing smoke. It has a cracked exhaust manifold, and potentially some imperfections on the cylinder wall. It starts promptly, runs smoothly and hasn't overheated.

Before stripping it down, I figured it was probably worth doing some investigation as I go.

Compression:
The compression values between the cylinders were actually quite consistent, with only 15psi difference between the lowest (#4) and the highest (#2). This is notable, as generally variation is of more concern than the values themselves.

...unless those values are only ~280psi. That seems substantially low to me, but happy to hear thoughts from the peanut gallery.





Somewhat lower than the benchmark of ~348psi. It is worth noting that this was indeed with a fully charged battery, on a warm engine, and with the valve clearances checked and set to the specified 0.20mm.

Glow plugs and injectors:
Pulling the GPs out for the compression test revealed that #3 was sooty all the way up to the thread. My understanding is that they are mean to seat and seal near the tip, which is consistent with the soot on the others. I didn't test them electrically, but I'll do so later.



I don't know enough about injectors to say much about them, other than that #1 and #2 were bathed in fuel, perhaps from the fuel return union, #3 looks a little rusty and was damp, and #4 seems okay I guess. These will all be gone through by a specialist in due course. They are Bosch items (made in India).



Other than that, the AC belt was past its prime, the low pressure hose between the power steering reservoir and the pump is leaking (again) and the P-gasket is weeping (again). There was also some oil around the flywheel housing - rear main seal or t-seals? Other than that, it is remarkably leak-free.

Fluids:
The coolant seems clean, with no evidence of oil contamination.

There was no chunks or abnormal glitter in the oil or on the sump plug magnet. Just for the hell of it (and because I was doing so for my old Benz anyway), I took an oil sample and sent it away for analysis. I don't have a benchmark for these values, but the diagnostic opinion seems promising.



There was what I would consider a typical amount of oil in the intercooler hoses (and presumably the IC itself), although I don't have much to compare it to. I am considering installing a Provent 200 once everything is back together to reduce the amount of oil it re-breathes.

[Shonky]

Whilst I will be doing the actual rebuild at home in my little one car garage, I am fortunate enough to have access to a large shed and a ute inconveniently located 200kms away. At least it means the rest of the truck is out of the way and undercover while I work.



A vehicles engine seems like such an intrinsic part of the car that to remove it can seem insurmountably complicated. Like most complicated things though, it's just lots of simple things put together. Have a checklist if you're new to it (or use the workshop manual) and just work through methodically. Label anything you aren't absolutely certain that you will remember the interface for, and if you're in an area with mice and mud wasps like I am, be sure to plug or cover any openings where you don't want a small creature to take up residence.

From memory, the workshop manual states to de-gas the AC and drain the power steering fluid. I feel that neither are necessary. Like many, I just unbolt the AC compressor from its bracket and cable tie it off to one side whilst still connected and do the same with the power steering pump.

In order to avoid making a mess when draining my coolant (or if I'm going to reuse it) I siphon out the contents of the overflow tank into a clean container, disconnect the branch of the bottom hose that connects to it and put a valve into the end of that. I used an old sprinkler system valve this time because it was lying around, but in the past I have used a pop-top off a sports drink bottle with a few turns of electrical tape around it with equal success. Now that the lowest point of your cooling system is connected to a handy hose with a tap, just feed it down through the engine bay and direct your coolant into a container. Zero mess.



Then, remove the drain plug for the block and make a mess.


Since I had to transport my engine home, I stripped it of most of its ancillaries and left them behind, and made up a pallet for it out of scrap timber.



Unfortunately, my engine crane decided to blow a seal just when I was ready to hoist it onto the ute, and as such I had to wrap it in glad wrap and come back a week later with a new ram to hoist it in and take it home. Once strapped down, it was very stable and didn't budge an inch on the trip back to the dojo.



And here we are, mounted on the stand and ready to begin slowly stripping it down, assessing as we go.

[Shonky]

As a bit of a time warp, when I pulled the engine I noticed this:



Clearly that leak I noted earlier was the rear main crankshaft oil seal (again), so probably good that it will be sorted also before contaminating the clutch.


I'm working my way through disassembling the motor, but going very slowly for two reasons. Firstly, I'm hoping to compensate for incompetence with diligence, and secondly because the prevailing wisdom is that taking the time to check tolerances and thoroughly inspect components yields important diagnostic information and gives a benchmark against the specs for reassembly.

Additionally, it presents a good opportunity to have something of a dry-run using some tools that I don't use regularly like the dial test indicator, and some new tools like the bore gauge and outside micrometers.


Most of the easy stuff has already been removed from the engine, leaving only the cylinder head, injector pump, timing case and belt, sump pan and rotating assembly.

Cylinder head:
After slackening off the valve clearances until the pushrods were unloaded, I removed the rocker shaft. The manual says to undo the fasteners working out from the middle. I worked inwards from the ends. Oops. Probably not a big deal, but worth paying closer attention in future. Immediately after removal I put a big cable tie through the bolthole at each end to stop everything sliding off the shaft and onto the floor. After pulling each pushrod, eyeballing them on a flat bench for any obviously bent ones (none noted) they were poked through a piece of numbered cardboard to keep them in order.

I had already loosened the head bolts (following the tightening sequence in reverse) while the engine was still in the truck, as it's easier than fighting with a breaker bar and an engine stand that wants to roll away, or deafening my quiet neighbourhood with the heavy duty battery powered ugga-duggas (HDBPUD^TM). This made it easy to zip the bolts out with the less aggressive of my impact drivers.



There was some discolouration around the rearmost aspect of cylinder 4. The vehicle has no symptoms of head gasket failure, but this does appear to me to suggest escaping combustion products? What say you, learned friends?




Timing case:
Surprisingly, the crank pulley came off with a minimum of fighting. Like the head bolts, I did this in the vehicle with it in gear. Initially I used a breaker bar but found that the force generated would overpower the clutch and turn the motor over before loosening the bolt. On this occasion, I did resort to the HDBPUD which made short work of it and paid for itself in that single event as far as I'm concerned.

Under the timing case cover, I was a little surprised to see that my relatively new 30,000km old timing belt seemed to be rubbing itself to death on the forward lip of the tensioner pulley. Additionally, one of the bolts on the injector pump timing pulley was completely rounded off and required careful Dremel surgery and an hour of fighting to remove. Not real impressive, considering this work was done at great expense by a Land Rover specialist mechanic.





After pulling off the injector pump, it's time to turn it upside-down.

[Shonky]

After rolling it over, I was greeted with a comical amount of silicon protruding from every orifice on the sump. The 300Tdi doesn't have a sump gasket, and by virtue of being attached to a Land Rover they are prone to leakage, but this was ridiculous. Excess silicon has a nasty habit of migrating into places it shouldn't be, and the consequences of it migrating into the oil pump would be fairly undesirable. Please, don't do this.



Peeling the sump pan off without bending it required some patience and a paint scraper, but I got there in the end. Happily it, looks quite clean in there, and there was no chunks of metal in the sump.

There was, however a few bits of plastic floating around in there... Annoyingly, much of it is evidently an off-cut of one of the t-seals. These were also trimmed unevenly, and the main bearing cap bolts holding them in appear to have been installed with a rattle gun resulting in damage to the heads. This would also have been when the engine acquired 2kg of silicon. Once again, this was work that I had paid a LR specialist workshop vast amounts of money to do. Sure, it's not a complete hatchet job but it doesn't exactly suggest that a lot of care or diligence was applied.



There was also this small, plastic washer that appears to have been munched at some point! I have no idea where it could be from. Any ideas?

[Shonky]

Before I started pulling everything apart, I thought I'd run the dial gauge over a few things.



First up, I flipped it over again and measured the piston stand-proud. This is entirely irrelevant as the block will be decked anyway and I'll have to do it again, but I was just curious to know what it was. Interestingly, the highest figure I found was 0.64mm at the front edge of Piston #3. This falls within the range where a two-hole head gasket is specified, but I had installed a three-hole (thicker) gasket when I did the head last time. From memory, this was recommended as something of a one-size-fits-all gasket, and seems to commonly be the go-to when you can't, don't or won't actually measure the stand-proud. I'll be sure to measure it properly and order the specified one this time.



I also checked the end float of the camshaft, which at 0.13mm is well within spec. (0.1mm - 0.2mm). The crankshaft end float was also good at 0.06mm, however the manual was unclear about the test conditions, and this was done with the main bearings and caps in place. One of the illustrations seems to show that this is tested with these removed. Any ideas?



I decided to pull the cam out first, so after gently sliding out the cam guides and rollers (and retaining them in order and orientation) I was able to gently slide out the cam. I've heard that cam bearings on a 300Tdi almost never wear, but mine seemed rough? Almost chewed up? There is no marks on the cam itself, and no copper showing to suggest wear, but it does seem a bit strange.

[peterjj]

I suggest checking the surface on the crank that runs on the rear crank seal. 300tdi will leak there with the slightest excuse.
I rebuilt a 300tdi myself and didn't do this and regretted it.

[Shonky]

Playing catch-up, after a prolonged period without reliable internet...

So this is why we're here, folks:







I'm no expert, but it appears that the big end and main bearings are utterly worn out. I'm rather surprised that nothing showed up in the oil analysis, although maybe the bulk of it has been and gone many services ago!

This probably explains the strange wine coming from my engine.




Otherwise, the pistons looked to be in good shape and measured up at 90.380 for pistons 1 and 3, and 90.390 for pistons 2 and 4. Wear specs are not provided for in the manual, but I wouldn't have thought that a maximum of .015mm would be unacceptable? (me from the future here: this is irrelevant, but more on that later. )

As an aside, I found these tubs at Bunnings for a fiver each, and they are perfect for keeping the assorted bits tidy, safe and in order.



While I had the block stripped down, I had a go with the bore gauge. Again, mainly for my own peace of mind and educational benefit.

The usual order of service applies: RTFM (read the ****ing manual), measure, record, compare. I made a spreadsheet and transcribed all the workshop manual ranges into it, then used conditional formatting so that when I type my findings into the box adjacent, the cell turns red if it's out of spec or green if it is within tolerances. Why? Because procrastination. I'll post it up eventually - someone might find it useful.







All measurements were reasonably close to the 90.470mm standard, with the largest diameter of 90.515mm found on the lateral axis midway down cylinder three.

[Shonky]

With the block stripped down, it was time to stop aimlessly prodding at it and give it to someone who knows what they are doing.

Squashing a 300Tdi block into the boot aperture of a Mercedes W123 was always going to be a tight fit, especially since being on my own necessitated using the crane, and not wanting to get oil all over my nice car necessitated it being in a tub. Turns out if you cinch the crane hook and the straps as much as possible, it fits with 40mm to spare!



I also handed over the pistons for measuring, main bearing caps to aid boring (I presume they use them to mount the engine in the boring machine perfectly aligned?) and the crankshaft for inspection and linishing. The machine shop will replace the welch plugs and cam bearings while they have it also.

I did notice this "wear" spot on the end of my crank on the thrust side of the driving flats for the oil pump inner rotor. I was a little concerned about this but some research suggests that this is normal, or at least acceptable.



Both Chris of Trailerfitter's Toolbox Videos (How to measure your crankshaft) and Mike of Britannica Restorations (Checking the 300Tdi crank) have videos specifically about 300Tdi crankshafts where this mark is clearly visible and doesn't rate a mention. These gents have proven experience with these engines, and I'm sure many of you will be familiar with their content. Considering they are confident enough to put their knowledge on the altar of public opinion and have proven to be excellent sources of information to me in the past, I am greatly reassured by this.

Speaking of crankshafts, I ran the micrometer over the journals and found them to be minimally worn with almost no ovality or taper. Well within spec.

I suggest checking the surface on the crank that runs on the rear crank seal. 300tdi will leak there with the slightest excuse.
I rebuilt a 300tdi myself and didn't do this and regretted it.

Thanks Peter. You're right - they're a bugger. Fortunately mine has no real scoring and seems to be in good condition. I wonder if it will also get linished along with the journals? I did double check it on your recommendation.

[Shonky]

The expert consensus from my machinist is that a rebore is required out to 020 thou over, and as such new pistons are required. I decided to splash out on a set of high-quality Federal-Mogul items, however there was a mix up and I ended up with adequate-quality Allmakes instead.



That said, it's a Land Rover, not a race car and I'm certain that these will be fine. The supplier was most apologetic and promptly made good on their error.

The crank and block are otherwise quite okay and I'm looking forward to getting them home and putting it all back together.

I picked out a colour for the engine the other day. I'll leave you hanging on that for now, except to say black is boring.