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Johan_B

Member Since: 20 Sep 2024
Location: Gothenburg
Posts: 19

2008 Defender 110 Puma 2.4 CSW Tonga Green

Puma pushing out coolant

My 2007 2.4 TDCI is ejecting coolant out of the expansion tank cap and also from the outlet elbow in the front of the cylinder head. Losses are small, in the range of 0,5-1 l per 2000 km. I suspect that the system becomes pressurized due to a cracked head gasket or possibly the head itself.
My question is, is there any other possible faults that can create a pressure in the cooling system? I have tried to read up on this kind of problem in other threads and it seems many also suspect the EGR cooler. Can a leaking EGR cooler also pressurize the cooling system, causing external leaks?

She has 140 000 km.
She was running hot on two occasions this summer. Very brief and rapid temperature rise according to the temp gauge, the entire episodes was over in 20 seconds roughly (plenty of stories on here with that behavior), and then back to normal.
Since then I have replaced the engine oil, nothing strange with the oil as far as I could tell. I replaced the engine coolant, no signs of oil in coolant but I could fit 1 liter more than I drained so definitely a bit low. I also replaced the expansion tank cap.
I now see visible marks of dried coolant on the tank and the outlet elbow.
No white smoke and she drives the best since we bought her in May.

I will try to obtain a CO2 test kit to see if there are exhausts in the coolant but for now I only improvised and secured a small plastic bag over the expansion tank (instead of the cap) to see if there was any gases coming out. There is a swirl and some bubbles in the tank but I suspect that is from the return line and that bubbles are caused by the movement in the tank rather than coming from the cylinders. Nothing happened during the short test with engine at 2500 rpm and I honestly don't know if I can draw any conclusions at all from that.

What can be ruled out and what should be the next step? All advice appreciated.

//Johan

3rd Nov 2024 10:16am

BrickBox

Member Since: 05 Oct 2021
Location: Wales
Posts: 818

2008 Defender 110 Puma 2.4 USW Zermatt Silver

Replace the expansion cap first. The pressure valve is common for failing and not opening.

Cheap fix, fingers crossed. 2008 2.4 110 Utility Station Wagon XS.

3rd Nov 2024 10:22am

andy63

Member Since: 30 Jun 2023
Location: north east
Posts: 514

The expansion tank cap has been replaced according to the post..

One way of establishing a head gasket failure into the coolant space is to use a scope with either a pulse sensor or a pressure transducer..
Connect the tube to the expansion tank in such a way as it doesn't suffer vibrational movement if you are using the pulse sensor..
If there is a leakage you will see it on the trace as a rhythmic rise in pressure , and if you use an injector as a cylinder reference you can even tell which cylinder is responsible.👍

3rd Nov 2024 1:29pm

Johan_B

Member Since: 20 Sep 2024
Location: Gothenburg
Posts: 19

Thanks for the replies.
Yes, the cap is only two month old and it has not leaked until this week. Worth a try with another one I guess.
The pulse sensor sounds nice but not in my tool box at the moment. Will keep it in mind if/when I consult with a workshop.

If the release valve in the cap is working as it should, would excess pressure still result in the leaks that I am seeing? Or would the gas just be released to the atmosphere?

3rd Nov 2024 2:58pm

Ianh

Member Since: 17 Sep 2018
Location: Essex
Posts: 1999

A faulty EGR cooler can let exhaust gasses into the coolant and pressurise the system. You could temporarily remove the two hoses from the EGR cooler, join them together, then run engine to see if the issue is rectified.

Noting a failed EGR cooler is a rare occurrence on a 2.4.

3rd Nov 2024 3:31pm

MK

Member Since: 28 Aug 2008
Location: Santiago
Posts: 2414

2007 Defender 110 Puma 2.4 SW Chawton White

Have you consider a combustion leak test? As well you could use a camera and check for bubbles coming into the expansion tank. Puma 110" SW

.............................................................
Earth first. Other planets later

3rd Nov 2024 3:34pm

andy63

Member Since: 30 Jun 2023
Location: north east
Posts: 514

Hi Ian... can a leaking egr cooler pressures the cooling system.. the exhaust gas manifold pressure is always tending towards atmospheric pressure with small pulses.. well below the pressure of the coolant on a running engine so how will it add pressure to the coolant system?
I can see gas been drawn into the coolant as things cool possibly..

And back to the op.. if the header tank cap keeps venting due to high pressure then it will carry coolant with it as it opens..Just like you get an eruption of coolant when you crack a cap on a pressurised system i imagine....

3rd Nov 2024 3:53pm

Johan_B

Member Since: 20 Sep 2024
Location: Gothenburg
Posts: 19

I was thinking CO2 test to begin with, if that is negative and problem persist a cylinder compression test. Am I right in avoiding pressure testing the cooling system if there is a risk of leakage into a cylinder?

Regarding the EGR cooler, I was hoping to take it out of the equation as I fail to see how it can pressurise the cooling system. If it is easy enough to bypass the cooler I’ll try that too.

Thanks for the advices so far!

3rd Nov 2024 7:24pm

MK

Member Since: 28 Aug 2008
Location: Santiago
Posts: 2414

Well, I guess you will get a + with the CO test being the source either from EGR cooler or blown gasket/crack head. So the best it would be to start by bypassing the EGR cooler as mentioned. I would be careful to make those hose connection quite safe not run out of coolant. Puma 110" SW

.............................................................
Earth first. Other planets later

3rd Nov 2024 7:43pm

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