strange coolant issue

[lexibo]

hi all new member here looking for some advice with a problem that as simply got me beat . i recently bought a 2014 1.6 tdci psa transit connect limited . but i have one niggling issue i would love to solve  . i seem to have excess pressure in the coolant and the level is high then the next day the coolant will still be pressurised but low . There is no sign of mayonaise in the expansion  tank no mayonaise on the oil cap no steam out of the exhaust the van runs lovely with no issues whatsoever other than this it as never overheated . it as all the signs of a an air lock but i doubt this very much as i had the timing belt  and water pump replaced by a garage but the symptoms still persist . now am i right in thinking that there are three ways that pressure can be introduced to a cooling system 1.head gasket failure but that would surely show other signs 2 oil cooler then i would expect to see oil in the coolant tank 3 egr cooler but would expect this to show up as white smoke from the exhaust . like i say it really as got me beat i love the van and want to keep it a long time but this is really spoiling it for me . any help advice would really be appreciated many thanks in advance and sorry for the long post

[Tdci-Peter]

13 hours ago, lexibo said:

i seem to have excess pressure in the coolant and the level is high then the next day the coolant will still be pressurised but low .

Are you having to add coolant when level is low, or does it recover to high level without any addition?

If the level is rising and falling without additional coolant, then I would say it is an airlock. Maybe a blocked de-gas hose or connection. The level will change depending on how much air gets trapped in the engine and pipework.

If you need to add coolant, I would say it was a small CH gasket leak. The gas pressure in the cylinder peaks at maybe 120bar, maybe more, so a tiny leak will force gas into the coolant to pressurise it. On a diesel, as it runs lean, it will take an appreciable amount of water added to make visible vapour (water droplets) in the exhaust. A small amount will produce invisible vapour (steam) in the warmed gas stream from the engine. Also emulsion will only form if enough water gets into the cylinders to pass through into the oil.

A CO (monoxide) test on the coolant can be done to see if it is getting combustion gas added, though I am not sure how well this works on a diesel, petrol engines produce more CO.

If there is a small CH leak, then in my experience, K-Seal works well to seal it up, though again that experience was on a petrol engine. But the mechanics of the CH gasket and how the sealant works are quite similar for petrol & diesel.

I have owned two fully aluminium engined cars, an Imp (!) and a Vectra. Both developed CH leaks. All my other cars had cast iron blocks and/or heads, with no CH leak problems.

 

[lexibo]

Hi thanks for the reply much appreciated .  the coolant was high and still pressurised yesterday even when the engine was stone cold so i removed the header tank cap slowly and took some coolant out i allowed the removed coolant to settle and noticed extremely fine specs of black dust on the surface of the removed coolant . now it appears that exhaust gasses are getting into the coolant . my problem is this could be the egr cooler or the head gasket both would produce this dust if leaking and also produce hydro carbons within the cooling system . that means the traditional HC test  of the coolant would not pinpoint the exact fault . so i am thinking of trying a bottle of k seal do you think it would be ok for these symptoms . i really do not want to spend x amount on the head gasket only to find it was the egr cooler 

[Tdci-Peter]

3 hours ago, lexibo said:

he coolant was high and still pressurised yesterday even when the engine was stone cold

It sounds like gas is being forced into the cooling system, pushing fluid back into the header tank. But the leak is either too small to allow coolant to flow back through it, or it is temperature dependant, or pressure dependant.

The pressure in the egr cooler exhaust side is only turbo pressure, about 20psi at full boost as exhaust back pressure will be similar to the compressor outlet pressure. So about the same as the coolant. The walls separating water from exhaust are quite thin, so I would expect a leak here to be bi-directional, gas in and water out depending on the relative pressures. (Some lorries have an exhaust throttle as an additional braking means, but I doubt if Transits have this.)

The gas pressure in the cylinder is over 80 times higher than the exhaust or coolant. The leak path is relatively long. So I can easily see this being a one way leak, cylinder to coolant only. Once the aluminium erodes enough to create little channels, then CH leaks do become bi-directional.

If it is a egr cooler leak, I doubt if K-seal will do any harm, it might even fix it for a while. If it is an early stage CH leak, then K-seal should work quite well, and may give years of useful life. Only an opinion, no guarantees! But best I can say.

 

[lexibo]

Hi once again thanks for your input really do appreciate it . i have put a bottle of k seal in today i followed the instructions to the letter so time will tell . i done plenty of research   before opting for the  k seal sounds like a great product just hope it does what it says on the tin . will update in a few days fingers crossed 

[lexibo]

hi all the problem is at last sorted . i put the k seal in and it made the problem much worse . so i took it to the garage for them to investigate they done a head gasket check and a coolant system pressure test and no faults found . all comes to all it was a partially sticking thermostat apparently it was stuck open but only a millimetre or two causing the coolant behind it to overheat hence the high pressure . i think the k seal actually worked and completely blocked the thermostat so not knocking the product it did work . so the garage power flushed the coolant system and replaced the thermostat and housing all sorted and running great . hope this helps others if they have the same symptoms 

[Jaydensaddy2009]

Hi could somebody help me I have just purchased a 2014 Transit Connect ltd with 52,000 on the clock and full service history. I noticed the water level on min today and the engine was cold so I opened the expansion tank lid and there was a lot of pressure in it and then the water level bubbled up and came back up to max. There is black soot mixed in with the coolant too. There is no cream or water in the oil it does not overheat at all and drives fantastic?? Could it be my thermostat? 

Edited September 13, 2020 by Jaydensaddy2009
Spelling mistake again

[Coldhard]

Hi Jayden, 

Exactly same problem as you currently.. what was the problem with yours in the end? Thanks in advance for the help!

[Tdci-Peter]

On 7/1/2021 at 7:39 PM, Coldhard said:

Exactly same problem as you currently.. what was the problem with yours in the end? Thanks in advance for the help!

Jayden's not been on site since last December, so may not see your question.

I suggest trying to get rid of any gas in the coolant system by running the engine up to temperature ('stat open) with the tank lid off or very loose, and topping up if it drops at all.

A stuck 'stat will not introduce gas into the system, but overheating will push steam or water out of the tank overflow. Then when it cools, air can be drawn in somewhere due to the partial vacuum in the cooling system. A cooling system is (or should be!) fully sealed, apart from the pressure relief valve in the tank cap, which should also be sealed unless under sufficient pressure.

A very small CH leak will slowly add gas in to the cooling system, especially when the engine is working hard and combustion pressures are highest. This added gas will pressurise the system even when cold. If the problem is persistent, and you are sure the system is free from any air or gas to start with, then a small CH leak is the most likely.