Coolant system pressurised after overheating. 300tdi.

the_wolf · Nov 14, 2016

I am in dire need if assistance gentleman and ladies. I recently punctured my radiator due to a rogue trolley (it came at me out of nowhere) and as such lost all of my coolant. I had to drive home and hope that it wouldn't overheat too much on the way. I made it to about 2 miles from home with the temp gauge moving between halfway and 3/4 before it decided to shoot up into the red. I pulled over onto the hard shoulder at this point with the engine making a hell of a chattering noise and then it completely died. Stopped for a bit before I thought I'd give it a go at restarting but it just turned over lazily a few times. I waited an hour and a half for it to fully cool down and in the meantime had called recovery but they were going to be another 90 minutes. It cooled down completely (once the steam and smoke had subsided) and I tried starting again. It started fine and sounded OK so I left it another half hour then decided to try and make it home. I did so without any issues and the engine sounded alright both when driving and at idle.
Got a new rad today and chucked the old one. Upon filling the coolant system I heard a hissing noise both from the thermostat plug and the header tank. I thought it may be a very bad air lock so I bled it as best as I could and tried again. This time however its pressuring the system so much that it's literally forcing coolant out of the header tank cap. I tried bleeding it as thoroughly as I could but it's still doing this so I think I'm going to have to accept that the head or the gasket is gone.
What's the best and worst case scenario I'm looking at? I've read that the gasket blowing at a certain point can cause the engine to pressurise the coolant but the level at which it's being forced out of the header cap is quite excessive. I'm hoping it's just a head gasket change, even if I did only fit a new one a couple of months ago.

David_Cooper · Nov 14, 2016

The problem with the 300TDI is that the water pump is mounted high up, so any significant coolant loss means the remaining water stops circulating very quickly..
I think it's very possible you've cracked the head

The Mad Hat Man · Nov 14, 2016

make yoself a low water warning system,

lynall · Nov 14, 2016

300 require bleeding and filling up a certain way.
Ive done a couple of head gaskets on 300 that have got so hot they had split the header tank, new head gasket and tank and away they went, so you may be in luck.

Why did you change the rad?

SpaceDawg · Nov 14, 2016

My guess would be if your lucky a head gasket, if not then you have done the head. I'd do the gasket and get it checked as well at the same time.

the_wolf · Nov 14, 2016

lynall said:
300 require bleeding and filling up a certain way.
Ive done a couple of head gaskets on 300 that have got so hot they had split the header tank, new head gasket and tank and away they went, so you may be in luck.

Why did you change the rad?

Said at the start, a trolley hit me in a car park and punched a very large hole through my radiator.

the_wolf · Nov 14, 2016

David_Cooper said:
The problem with the 300TDI is that the water pump is mounted high up, so any significant coolant loss means the remaining water stops circulating very quickly..
I think it's very possible you've cracked the head

SpaceDawg said:
My guess would be if your lucky a head gasket, if not then you have done the head. I'd do the gasket and get it checked as well at the same time.

Aye that's what I'm fearing. I'll get the head off on Thursday when I'm off work and I'm keeping my fingers crossed that its just the gasket but I don't have a lot of hope. If I've cracked the head will it be obvious to see? I don't really have the time to get it checked properly unfortunately as I work a lot. If it's duff then I can get a new (read used) one I guess

the_wolf · Nov 14, 2016

The Mad Hat Man said:
make yoself a low water warning system,

I'd looked at that a while ago but I don't think it would have helped in this case lol the hole in the rad would have made it null and void.

the_wolf · Nov 14, 2016

What does anyone think of the radiator being partially blocked? Would this cause such drastic overpressurisation? If so is there an easy way to check and unblock it?

David_Cooper · Nov 15, 2016

I don't think a furred up rad would do that.. but you can check to see if the rad is getting hot all over (if it will run long enough to get up to temp without spewing all the coolant out).
Any cold patches on the rad mean that section is not doing anything.

lynall · Nov 15, 2016

the_wolf said:
Said at the start, a trolley hit me in a car park and punched a very large hole through my radiator.[/QUOTE

To be fair to me the lack of spaces etc made it hard to read, so I skimmed the main points, obviously missing the bit where you rammed the trolley.

You most likely wont be able to see if the gasket is blown, well all the ones Ive done Ive never seen anything obvious apart from n04 cyl on the 200.

The Mad Hat Man · Nov 15, 2016

the_wolf said:
I'd looked at that a while ago but I don't think it would have helped in this case lol the hole in the rad would have made it null and void.

Mine is triggered by low water level or overheat...... turns on cooling fans and triggers a warning light on the dash .
Also carries out a check prior to engine run

flat · Nov 15, 2016

Rather than sod about with the rad - which is unlikely to cause over pressurisation - just get a 'sniff test' of your coolant done to see if there are by products of combustion in the coolant - if there is the head gasket is gone (and maybe the head is cracked/warped - depends how hot it got).

The coolant system doesn't pressure (when functioning correctly) due to anything generating pressure - it pressurises due to the thermal expansion of the coolant.

If yours is dramatically pressurising then it will be because one of the engine cylinders is physically pumping the pressure up. Hat only happens when the head or HG is gone

Sorry

mojo247 · Nov 15, 2016

you can sometimes do a visual inspection for cracks on the CH and it should be pretty obvious where (or if) it's coming out from.

Turner engineering do a good replacement or you could chance it on ebay!

Check the engine block a well for signs of leakage!

the_wolf · Nov 15, 2016

The Mad Hat Man said:
Mine is triggered by low water level or overheat...... turns on cooling fans and triggers a warning light on the dash .
Also carries out a check prior to engine run

Aye but you're an electrical genius

. I'll have a look at something like that when it's running again, still got the viscous fan fitted too and I'm happy with that.

flat said:
Rather than sod about with the rad - which is unlikely to cause over pressurisation - just get a 'sniff test' of your coolant done to see if there are by products of combustion in the coolant - if there is the head gasket is gone (and maybe the head is cracked/warped - depends how hot it got).

The coolant system doesn't pressure (when functioning correctly) due to anything generating pressure - it pressurises due to the thermal expansion of the coolant.

If yours is dramatically pressurising then it will be because one of the engine cylinders is physically pumping the pressure up. Hat only happens when the head or HG is gone

Sorry

Its ok I'm resigning myself to the fact that the head maybe has damage. Worst case scenario that's all it is, I'm just hoping it doesn't have scoring in the bore as I came across that when I was looking it up.
Judging by the smokey looking stuff in the header tank I'm guessing it does have some sort by products of combustion in it. I can't get it anywhere to get a sniff test done but I'll speak nicely to the local garage and see what they can do.

mojo247 said:
you can sometimes do a visual inspection for cracks on the CH and it should be pretty obvious where (or if) it's coming out from.

Turner engineering do a good replacement or you could chance it on ebay!

Check the engine block a well for signs of leakage!

I wish I had the money for a Turner Engineering one but it'll have to be a second hand jobby I remove myself unfortunately. I can get it tested at a local engineering place before I fit it though.

Either way I'm going to have to remove the head so I might as well get that over and done with.

flat · Nov 15, 2016

You can buy sniff test kits online or eBay or whatever.

Head off seems inevitable, at least you will see if it's the gasket or the head. A local engineering firm or garage should be able to skim and pressure test the head for you, then it will be just refit with a new gasket.

As your going to be in there with it all dismantled its worth thinking about what else would be with changing whilst it's in pieces, cambelt, etc.

You would hate to put it back together then a month later take it apart again for a different job

the_wolf · Nov 15, 2016

flat said:
You can buy sniff test kits online or eBay or whatever.

Head off seems inevitable, at least you will see if it's the gasket or the head. A local engineering firm or garage should be able to skim and pressure test the head for you, then it will be just refit with a new gasket.

As your going to be in there with it all dismantled its worth thinking about what else would be with changing whilst it's in pieces, cambelt, etc.

You would hate to put it back together then a month later take it apart again for a different job

Spoke to an engineering place that a friend recommended and the guy knows 300tdis well. He said that he's never seen one crack yet so it's more than likely badly warped. It can be skimmed and then will need the stems and valve seats cut to accommodate. He said it's not much more work than skimming it normally so at least it sounds repairable.

flat · Nov 15, 2016

the_wolf said:
Spoke to an engineering place that a friend recommended and the guy knows 300tdis well. He said that he's never seen one crack yet so it's more than likely badly warped. It can be skimmed and then will need the stems and valve seats cut to accommodate. He said it's not much more work than skimming it normally so at least it sounds repairable.

Excellent, that's encouraging

Kwakerman · Nov 15, 2016

As mentioned above the 300 pump is set high, you also need to remember that it is the coolant temperature on the end of the temp sensor that is actually being read. If there is no coolant on the end of the sender then it is exposed to air (albeit hot air) so it may under-read due to lack of heat transfer medium. That probably means that if the gauge reads slightly higher than normal (with water) then the reality is that without water for the same gauge reading the physical temperature probably a lot hotter than you think. All a bit of guess work as I don't want to try proving it with my engine!

The Mad Hat Man · Nov 15, 2016

Kwakerman said:
As mentioned above the 300 pump is set high, you also need to remember that it is the coolant temperature on the end of the temp sensor that is actually being read. If there is no coolant on the end of the sender then it is exposed to air (albeit hot air) so it may under-read due to lack of heat transfer medium. That probably means that if the gauge reads slightly higher than normal (with water) then the reality is that without water for the same gauge reading the physical temperature probably a lot hotter than you think. All a bit of guess work as I don't want to try proving it with my engine!

All the more reason why a low coolant level sensor is important on 300TDi's

Coolant system pressurised after overheating. 300tdi.

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