Hi all. I have very strange problem with my Mercedes e320 cdi 2003 inline engine. Even when engine is stone cold,there is big amount of pressure in coolant system. No antifreeze lost,no overheating,no mixing coolant with oil. Car goes like a charm,no smoke from exaust. Already have change water pump,thermostat,reservoir and cap. Cooling system is flushed with fresh Fuchs fricofin antifreeze mixed with destilled water. Some help on that will be highly appreciated

 

I'll bet a cooling system pressure test will reveal a blown head gasket

If I'm not mistaken there are also kits available to test for combustion products (exhaust) in the coolant.

 

Thaks for answer. But no,it is not head gasket or head. Already check. It is very strange situation. No even a single sign of engine problems. No mixed fluids,no smoke,no overheating. Just this hard like stone pipes and pressure in cooling system. It is going insede air from anywhere,which have no sense. Very very strange

 

how are you noticing pressure, are there any abnormal symptoms?

 

When i open cap with cold engine there is large amount of pressure and lots of air go out from reservoir. And no,there is not nothing abnormal. Cooling system is bleeded many times,but some way air is getting inside the system

 

I bought an '05 DMax truck years ago. The hoses stayed pressurized after cooling down overnight. Drove perfectly fine, just like yours. Oil was clean, coolant was clean. After a year or so and a trip across the country it started to push coolant out the overflow. Then it started to push a LOT of coolant out the overflow. I changed the head gaskets and found a tiny (TINY) crack by cylinder #7.

Gonna stand by my original advice... But look forward to hearing how you fix the problem.

Head gaskets. I'll bet a beer (real beer, not any Budweiser product) on it. Atomspheric pressure isn't going to get into your cooling system. The cooling system should pressurize when the engine gets warm/hot thanks to expansion of fluids, but should retract to pretty much zero pressure after completely cooling down. Unless something is added to the system (combustion pressure). There's nothing that would do that except a crack either in the block, gasket, or head.

 

I drive car with this symptom last 60000 kms and 2 years.I know there is problem but not sure it is head or gasket. Also mechanics here told me just drive and when there is some differant symptom will see what to do,they are not sure also abouth head or gasket,but there is no nothing differant

 

Not sure what country you're in, but in the US, Walmart sells a kit for about $50 called the Combustion leak tester. Basically it checks for combustion gases in the anti-freeze. As someone else said, that's probably what you have going on.

https://www.walmart.com/ip/COMBUSTIO...&wl13=&veh=sem

 

I am from Bulgaria and also have same test here.Have made 3 different tests. No exhaust gases in coolant