Jump to content

300TDi cooling woes


elbekko
 Share

Recommended Posts

I've been battling this damn thing for months, and I'm about ready to boil harder than my engine (if that's even possible).

This is all in a softdash Rangie, so the heater etc is all of the Disco type.

A few weeks back, I was stupid enough to let the coolant (read: water) freeze with temperatures around -10°C. Had it trailered to the shop, let it thaw for over a day, replaced the water pump which had broken, and filled with some coolant that's good up to -37°C (because I like overkill). On my way home from the shop, it overheated. Let the pressure out, refilled with coolant, and onwards. From then on no problem for a few weeks.

This tuesday I do a little trip, about 50km each way, pretty much all motorway. No problem going there and back, but when I want to leave at home again 30 minutes after arriving, she starts overheating instantly. Went back, temperature dropped back to normal when I turned into my street (seriously now?), let it cool, and checked coolant level: all normal.

Next day, again a mainly motorway trip, about 80km each way. About 4 or 5 hours between trips, no problem.

Next day I check my coolant level, it's overflowing. When it stopped coming out, I went on my way, and it overheated quickly enough. I was on my way to class, so not too happy with that :angry: Stopped, let the pressure off again, continued. Temperature rose, but I only had about 3km to go until I was at school, so I went on. When I turned into the school parking lot, engine now capable of flash-boiling an egg, I hear a loud gurgle coming from somewhere near the heater matrix (I think), the temp shot down to normal, and the heater started working again. Refilled again, and back to normal...

Today same story, happened twice after a bit of driving and recovering, had to let the pressure off two or three times until the air pocket came out and I could refill. After that it went back to normal.

Honestly, I'm stumped. Only thing I can think of is that it's drawing air somewhere around the heater matrix, which then somehow gets to the thermostat and makes it not open anymore.

Any bright ideas? If you guys can solve this, consider a donation to the forum a done deal.

Link to comment
Share on other sites

I'm just battling temperature woes on my 200tdi at the moment, somthing you may have to consider is that your head gasket could be blowing into one of the jacket coolent galleries, it is possible for the head to go without hitting oil etc. thats one way it could be pressurising your system... other than that it sounds like you could have an awkward air lock somewhere... I belive that's what I'm chaseing at the moment.

Link to comment
Share on other sites

Yes, a blown head gasket was my first thought a few months ago too, but dismissed it because you couldn't feel any pressure coming from the coolant circuit, nor is any bubbling visible.

The problem with the air lock is that it keeps coming back. I've let enough air out of the system to fill a balloon by now :blink:

Link to comment
Share on other sites

I had a similar problem with a 300Tdi Defender a few years back. The problem lay with the bleed hoses from the thermostat housing and top of the radiator to the expansion tank. The circular disc shaped union just below the expansion tank had blocked so that neither the head or radiator would self bleed. The hoses were also pretty choked.

A simple check is to take the cap off the expansion tank when everything is cold and the coolant filled to the correct level. If you raise the engine revs to 2000 - 2500 rpm then the thermostat will be closed and coolant should flow through the engine, through the heater matrix and back throught the bleed hoses to the expansion tank. The return flow should be evident under the surface of the coolant in the tank. No flow and there will be a good chance that something is blocked. This test only works with a cold engine as the thermostat needs to be closed.

It's not a big job to clear out the hoses. While you are at it, I would change the circular disc shaped union as they are renown for splitting at the most inappropriate moment!

Link to comment
Share on other sites

I Can truely sympathise having spent weeks trying to source the over heating under load problem on my Disco 300tdi.

Few questions

1. Before the freeze was everything ok?

2. Have you sniff tested ?

3. Is the thermostat ok... drop it i boiling water see if it opens

4. Is your 'p' gasket ok?

5. Is the heater getting hot inside the car or does it blow hot and cold?

6. Did you replace the water pump with a genuine one?

HTH

Tony

Link to comment
Share on other sites

1. Before the freeze was everything ok?

Yes and no. I was chasing down a few leaks and airlocks (probably the same ones as now), hence the water in the system. It overheated a few times then too.

2. Have you sniff tested ?

Smells like coolant, not exhaust.

3. Is the thermostat ok... drop it i boiling water see if it opens

I'll check. Is it possible it only works sometimes?

4. Is your 'p' gasket ok?

That's the one behind the water pump right? As far as I can tell, there aren't any leaks there, and it looks as if it's been sealed with liquid seal.

5. Is the heater getting hot inside the car or does it blow hot and cold?

When it's behaving normally, the heater works as it should. When it's overheating, only cold air comes out.

6. Did you replace the water pump with a genuine one?

As far as I know, yes. It's the one from my old block.

I'm affraid your head or engine block has developped a crack caused by the expansion of the ice...unfortunately that's a common problem with current temperatures...

Obviously that's the answer I wasn't looking for :lol: It's a possibility, but as I said, no bubbling in the expansion tank, no smell of exhaust, no coolant seems to be disappearing under normal operation, ... I haven't checked the oil yet though, but I've been told TDis don't crack between the coolant and oil circuits.

Link to comment
Share on other sites

When it's behaving normally, the heater works as it should. When it's overheating, only cold air comes out.

To me, this signifies an air lock, without doubt.

Have you an idea of how much coolant you've put in?

Have you tried manually bleeding the heater and thermostat bleed hoses by opening the joints, with the header tank lid off?

Link to comment
Share on other sites

To me, this signifies an air lock, without doubt.

Have you an idea of how much coolant you've put in?

First time I filled it after replacing the water pump I'd say about 6l.

Have you tried manually bleeding the heater and thermostat bleed hoses by opening the joints, with the header tank lid off?

I'm not too sure what you mean by opening the joints?

I've always bled the system by opening up the radiator and thermostat caps, filling the radiator, replacing that cap, then the expansion tank, let it run, and fill up until level in expansion tank is good.

Link to comment
Share on other sites

I'm not too sure what you mean by opening the joints?

I've always bled the system by opening up the radiator and thermostat caps, filling the radiator, replacing that cap, then the expansion tank, let it run, and fill up until level in expansion tank is good.

Having recently worked on a 300tdi, we had to repeatedly release air from around the engine, having got it to operating temperature, so the 'stat opened. That was on a rear-rad challenge truck, so the positioning and heights of the engine/rad/header tank isn't standard.

On my 200tdi, I have on occassions removed the block to heater pipe, and let a large amount of air escape there. This is much quicker than waiting for the air to work its way around the system.

Link to comment
Share on other sites

The TDi RRC has similar problems, the expansion tank isn't the highest point in the system, which makes it a total arse to bleed.

I'll try removing the pipe(s), see if it helps. Tomorrow though, not in the mood for it today :angry: Sometimes you just feel like going out and buying a Toyota to tow the LR to the scrapheap :unsure:

Link to comment
Share on other sites

I agree with Luke, definately sounds like an air lock. I have found that if you unbolt te expansion tank and lift it up and then bleed it from the caps, then run it up and carefully release the pressure from the thermostat cap, keep doing this until no more air comes out, then re-fit the expansion tank.

On a side note i would try flushing the cooling system a few timesto try to aid ciculation

Link to comment
Share on other sites

Well, I just checked.

As for the bleed pipes, the symptoms are there (no visible flow at high rpm with cold engine). No source though, as they all seem to flow fine.

Disconnected the heater hoses, lifted the expansion tank until coolant came running out, reconnected the hoses (did this for both hoses separately).

Opened up the thermostat cap, lifted the tank until it came running out of there, and closed the cap.

Let it run a bit until the gauge said the temperature was fine. No discernable heat coming from the vents :blink:

Didn't go for a drive to see if it would overheat though.

During all of this, a little bit of coolant spilled out of the hoses and thermostat. The coolant level was higher afterwards than when I started :blink:

I think I need an exorcist or something.

Link to comment
Share on other sites

During all of this, a little bit of coolant spilled out of the hoses and thermostat. The coolant level was higher afterwards than when I started :blink:

Sounds like the air lock got worse, rather than better, then!

During all that, did you have the lid off the expansion tank? You need to, if you don't the air lock in the top of the tank stops the water flowing out of the header tank!

I have previously separately bled the heater pipes by disconnecting both ends and using water from a hose pipe to fill the heater system, that was on my 90 though, don't know how possible it is for you.

Link to comment
Share on other sites

Well, I just checked.

As for the bleed pipes, the symptoms are there (no visible flow at high rpm with cold engine). No source though, as they all seem to flow fine.

Did you remove the pipes and union to check each one individually?

Also, is the correct style thermostat fitted? Ones without the disc below the spring make it far more difficult to bleed air from the system. IIRC, there should be a small hole through the main disc of the thermostat, with a little plastic float rattling around. This should be at the twelve o'clock (top) position.

Link to comment
Share on other sites

Did you remove the pipes and union to check each one individually?

No, I just disconnected each one separately and held it under the level of the expansion tank and waited until coolant came out.

Also, is the correct style thermostat fitted? Ones without the disc below the spring make it far more difficult to bleed air from the system. IIRC, there should be a small hole through the main disc of the thermostat, with a little plastic float rattling around. This should be at the twelve o'clock (top) position.

Yes, it's a genuine one, that has worked fine for quite some time in my previous 300TDi (I swapped it over a while ago after the first bout of overheating when one of the heater hoses had a leak).

Link to comment
Share on other sites

Have you read through Fozsug's recent extensive thread on 300Tdi overheating issues?

Also , have you done a chemical sniff test for HG failure/cracks?

Another good test is to pressurise the system without the engine running and leave to see if the pres. drops- you obviously need a gauge in the bung in the header tank to monitor it .

These are both tests a local independent garage should be able to do for you while you wait.

Have you checked under the front footwell carpets for heater matrix leaks?

...maybe its all the snow stuck in the front grille? :P

Jealous? moi? :D:D

Back to serious suggestions , if you disconnect the hose from the back of the head to heater and clamp the garden hose onto it you can flush thru the heater and back thru the block/head to see if there is any muck coming out of the pipe stub on the head.Leave all bungs in and cap on HT.

One telltale for a blown HG is the exhaust port(s) affected are usually much cleaner than the others when you take the manifolds off

hth

Steveb

Link to comment
Share on other sites

Have you read through Fozsug's recent extensive thread on 300Tdi overheating issues?

Yes, I think I have. I've considered the system being gunked up, especially as I don't know what the previous owner has done to the engine, but the symptoms don't fully match. With him, the temperature shot up under load, and came back down when taking it easy. Not so for me.

Also , have you done a chemical sniff test for HG failure/cracks?

As I've said above, the coolant smells like coolant, not exhaust or anything like that.

Another good test is to pressurise the system without the engine running and leave to see if the pres. drops- you obviously need a gauge in the bung in the header tank to monitor it .

I did that a while ago, which led me to a leak in one of the heater hoses. Repeated after replacing the hose and heard only the expansion tank cap let out air. I'll redo it next time I'm in the shop.

Is there any chance the air I blew in then somehow formed a hard to get out air pocket? I connected to compressor to the radiator bleed hose, as that was easy to cap off and fit the pipe we have fabbed onto the compressor for this stuff.

Have you checked under the front footwell carpets for heater matrix leaks?

What carpets? :lol: Took those out after my first big dive. No wetness there.

...maybe its all the snow stuck in the front grille? :P

That is indeed when it started acting up again last time, cleaned that out, but it didn't solve anything. I guess the overheating from the snow put enough pressure on the system to dislodge the airlock from somewhere harmless to somewhere annoying.

Back to serious suggestions , if you disconnect the hose from the back of the head to heater and clamp the garden hose onto it you can flush thru the heater and back thru the block/head to see if there is any muck coming out of the pipe stub on the head.Leave all bungs in and cap on HT.

I did about that - unhooked the heater outlet hose, raised the expansion tank, and waited until it came running out. Didn't take very long, and no discernible muck came out.

One telltale for a blown HG is the exhaust port(s) affected are usually much cleaner than the others when you take the manifolds off

I guess I could check that, but that would require me to get back to the shop (and having time... damn exams coming up), as my collection of tools at home is limited to a socket set, a not quite large enough hammer, and a few bent screwdrivers.

I could probably drop her off at the local independent (other than us, where I'm supposed to be the diesel guy :ph34r: ), but that would mean waiting a few weeks as it's a very busy shop.

Link to comment
Share on other sites

Give the others a good scrape/gentle tap with a small punch/screwdriver/chisel to check. They always rust from the inside.

Knock the new one(s) in and run it up.

You may find that the HG has blown also depending how hot it all got, although it sounds like you have been topping up coolant regularly.

Good to find the culprit :)

cheers

Steveb

Link to comment
Share on other sites

HG should be fine, never let it run hot for more than 2-3 minutes, and the main 'hotness' came from the thermostat closing due to steam buildup, not lack of coolant.

I'll gladly replace all the ones on the side, but those on the back are fairly impossible to reach without taking the engine out or the body off :blink: (or hiring a leprechaun)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy