Thread: 300tdi intermittently oveheating

Blknight on here posted this for bleeding the cooling system. Works for me.

the other option(I think better than the extended bottle on the reservoir trick) is to buy yourself a pressure bleeding/testing kit.
I got mine off ebay. Whilst not used all that much, still worth the money.

Reason for using the pressure test kit is that you bleed it cold, hence don't have the trouble of getting the coolant hot and burning yourself silly trying to bleed.

Also, you can pump in a lot more than 15psi, I usually get it to 20+ psi, and with more pressure makes it easier to bleed right too.

The better, more complete kits usually sell for about $70-80(ebay, amazon, etc) and the bonus of these full kits is the vacuum(venturi, where you need a compressor!) attachment that makes coolant recovery a breeze.

But don't assume that bleeding will be your issue. When you say changed it to a new car, that is you got another car, and swapped engine only? .. what about coolant, heater matrix, etc? If these are what the new car had and you only installed the motor, could be a dud radiator, or leaking heater matrix or something wrong with the new car body.

The other question is what condition is the non-return valve (from thermostat to expansion bottle) like. I think they can gunk up and not work well. So, if you used the one in the new body, and you don't know it's condition, may pay to check it/replace it or something, but don't remove it and replace with just a straight hose. Cooling system needs this non return valve.

Hi Arthur,

Thank for that.

Some history of this car (the white one) and the engine that's in it now.
He has had the car for a while, and has done about 10k km, since getting it.
In January it developed a knock that turned out to be no. 4 big end, and a range of other issues.
Details here.
300Tdi engine knock

We swaped the engine and manual gearbox from an old somewhat ratty Disco (the green one) he has had for a few years, info about that swap in my last post of that thread.
This car/engine was bought cheap with a blown headgasket and has done two since, both with a known cause that we thought we had resolved

Since Riley started this post it has pushed out coolant and started over heating 3 or 4 times.
Each time the expansion tank as been over full, and the thermostat housing has been empty.
So it's getting gasses into the cooling system somewhere, that can only be headgasket! Though Dave (Blknight.aus) did cheerfully list a range of other more serious things it could be, in a thread I started about this engine some time ago.

Each time it has been filled though the thermostat housing, this is the way I've always done my Defender and how we've always done Riley's Disco's, so I don't think bleeding is the problem.

Temperature he has quoted is from an Engine Watchdog on the thermostat housing.

The original engine from the white one has a good head, near new according to the engine machining guy.

So unless someone has a simpler idea it looks like we're doing another headgasket.

Re the valve in the thermostat/radiator bleed line, it was the one from the white car, so was OK when it was running.
It has since been replaced with a straight though brass fitt as it was weeping coolant, I was going to send him the one out of the green car, but I broke it☹️. When I checked it it had no flow restrictions in any direction on any combination of the three pipes.
Are you saying this is wrong?
And that its important?
I have read on here of several people running a straight though brass fitting with no ill affects.

As always thanks for everyone's ideas.

Tony

My thoughts (but you won't like them.)

Cracked head, warped block.

Could also be a cracked bore.

However, if you keep replacing the head gasket and it keeps letting go in one visible spot - the same one, everytime, there could be muck in a head bolt hole stopping it doing up properly.

Not fun for you I know.

yeah, I'm thinking same as Shack.

I remember Mike at Brittanica Restoration(you tube) had a kind of similar issue on one(or many!!) ... but this one episode in particular where he tests the heads in a bath of hot water. And it only showed up in the hot water, not just a pressure test(i.e. cold)

The only part of this answer is that it kind'a ignores the info that you said, for 5K klms that same engine on the old ratty D1 was fine, up until it was transferred to the current white one.
I'm not seeing how transferring from one body to another will magically develop a crack in the head, other than coincidence.

I'd try a coolant gas test kit to confirm, rather than do another head gasket and end up at the same situation.

I wouldn't ignore the coincidental nature of repairing stuff. Nephew had it on his D2a, I had it on my coffee machine recently(cleaning machine suddenly caused the water pump to fail).

For the cost of a gasket(or some gasket goo), waterpump is an easy check to do too. could be a dud impeller. Just be mindful of the three longer lower bolts, they can snap easily.
With the lack of coolant in the thermostat and it all being in the expansion and rad ... could be a low/no flow problem.

Originally Posted by AK83

yeah, I'm thinking same as Shack.

I remember Mike at Brittanica Restoration(you tube) had a kind of similar issue on one(or many!!) ... but this one episode in particular where he tests the heads in a bath of hot water. And it only showed up in the hot water, not just a pressure test(i.e. cold)

The only part of this answer is that it kind'a ignores the info that you said, for 5K klms that same engine on the old ratty D1 was fine, up until it was transferred to the current white one.
I'm not seeing how transferring from one body to another will magically develop a crack in the head, other than coincidence.

I'd try a coolant gas test kit to confirm, rather than do another head gasket and end up at the same situation.

I wouldn't ignore the coincidental nature of repairing stuff. Nephew had it on his D2a, I had it on my coffee machine recently(cleaning machine suddenly caused the water pump to fail).

For the cost of a gasket(or some gasket goo), waterpump is an easy check to do too. could be a dud impeller. Just be mindful of the three longer lower bolts, they can snap easily.
With the lack of coolant in the thermostat and it all being in the expansion and rad ... could be a low/no flow problem.

More news from the troubled 300tdi,

I have a friend who works at a mechanic, he has been helping me try to diagnose these issues. We did coolant gas test with one of those plungers with a colored liquid... This came up clear, no exhaust gas in the coolant.

I've just replaced the plastic y piece with a new one (the proper one, not a generic t piece) and drove home.
The car came up to temp but only for 5 mins or so as I neared home (80deg), I checked the levels when I got home and sure enough the expansion tank is full to the brim and the thermostat housing is empty again.

I'm 99% sure all hoses are on the right way and stuff like that, I pulled the main belt off and checked the water pump bearing which seems normal enough, I suppose the only way to tell if the impeller is the problem would be to pull it off as Arthur suggested, I think that will be my next step.

I've been talking to Dad (Tony C) and we figure there has to be gasses getting into the system somewhere for the coolant to be pushed up into the expansion tank, or could a faulty water pump not providing enough flow cause this???
In any case i will pull the water pump for a look before we embark on yet another headgasket replacement.

Thanks again,
Riley

Given how lean a diesel runs at idle, is it possible that the gases the test measure are so diluted the test doesn't pick it up?

Tony

just on the off chance, and only mention this because it could be done .. are the fan blades facing the right way around?

If you guys, or someone previously did work and changed the viscous hub, the fan can be unbolted from the viscous and could potentially be fitted wrong way around.


I remember first time I tried to remove the viscous hub, and didn't realise it's turning the 'wrong way'. That is, to remove it you have to 'do it up'. So with that in mind and engine running(at idle of course) check that the fan is pulling air to the back of the engine.

Has the viscous hub been ruled out as a dud too?
Couple of ways you can test it:

Easiest is if you have a heat gun. heat the front of it gently, and it won't take long. the coiled up spring should slowly move. This opens the valve to allow the silicon to move about within and lock it up(kind'a).

What I do now is to pop the nut end into a vise and spin the fan by hand. It could be a bit stiff to start with when cold(normal) then start to free up and spin freely. Then use heat gun on the coil, and it should be obvious when it winds itself.
I think it only needs to be about 80-90° ish and it will open the internal valve. Then while its still hot, try to spin fan again whilst on the vise. it may still start off a bit free, but then begin to offer resistance. if it never has any resistance while it warm, it's dud.

The other, dangerous, method is while still on the car, and engine got hot and motor off, hold fan with thick gloves or lots of cushioning and get someone to start engine and hold onto fan. at first it may feel free, but with a small amount of time it will start to spin on you.

That bleed valve thingy is important. Was on mine anyhow. I had same issue where it was leaking and I put a normal t-junction too. but then I had overheating issues and someone mentioned this little device. The mod I was suggested was to squeeze a small tube into the port coming from the thermostat in the T-juntion, but make sure that the small tube doesn't get sucked through too, so open up one end of the tube to shape it like a funnel. Was a bit of mucking about and I had the vacuum line that fit perfectly. Otherwise everyone recommends to use a Y junction, and not a T.
Anyhow, if new proper part is fitted shouldn't be a problem.

One last question about this issue. Does it happen on a highway drive only? does it happen around town driving too?