Loosing coolant but no leak after pressure test

[Michael r]

Hi all new here..

My head is totally gone so was loosing coolant without any leaks visible had a new belt and pump fitted was working great for a week and seems to go again had a new seal popped on the expansion tank was ok for a day or so then came back up on screen we have had a pressure test no signs of leaks when I open the the expansion tank the pressure brings the coolant straight back up also had a head gasket test and stayed the same colour no over heating am all out of options any help would be great 

[Stevey Y]

1 hour ago, Michael r said:

Hi all new here..

My head is totally gone so was loosing coolant without any leaks visible had a new belt and pump fitted was working great for a week and seems to go again had a new seal popped on the expansion tank was ok for a day or so then came back up on screen we have had a pressure test no signs of leaks when I open the the expansion tank the pressure brings the coolant straight back up also had a head gasket test and stayed the same colour no over heating am all out of options any help would be great 

Hi it could well be the thermostat playing about the flow will be the same because of the bypass system if its only partially opening it may cause steam which vents through the expansion cap on the expansion tank.

Steve.

[Michael r]

Hi Steve is that the thermostat housing your on about a was talking to a lad he said could be that matrix heater or have a air lock in the system and to flush it as heating comes on hot then cold... But yeah someone did say that the thermostat could be staying open rather then open/close 

[Stevey Y]

4 minutes ago, Michael r said:

Hi Steve is that the thermostat housing your on about a was talking to a lad he said could be that matrix heater or have a air lock in the system and to flush it as heating comes on hot then cold... But yeah someone did say that the thermostat could be staying open rather then open/close 

Hi sounds like a thermostat from the symptoms you describe, its a pretty straight forward change I doubt the heater matrix wants flushing but it certainly wont do any harm.

Steve

[Michael r]

Ah smashing I have done everything apart from that going to give the engine a flush and get this fitted next weekend and pray it works its the pd engine people say there bomb proof am really doubting it now lol 

[Michael r]

Just a quick 1 got speaking to a guy from a. Garage the day and he said it's possible a would have a crack on the head but there is no smoke coming from the back or over heating could that still be the case ?

[cliffcoggin]

The head doesn't crack without good cause such as being incorrectly fitted (which would have showed up soon after fitting), or the engine has seriously overheated which you said has not happened.

[Michael r]

Keeps at 90 no smoke from back but coolent has to be going somewhere and someome from a garage said only thing he can think is a cracked head or on its way out it popped up check level went over the 90 yesterday withing 10 seconds went back to 90 and light went off car has me head all over lol 

[cliffcoggin]

Unless I missed something we have not established what engine we are discussing. If it is a diesel the loss could be happening via the EGR cooler.

[Michael r]

Yeah its a 1.9tdi the Pd engine in a Audi A3 every garage a go to literally say a different think most say head is gone but there is only loosing coolant sign no smoke for exhaust or overheating just comes on every few days or so to check coolant 

[cliffcoggin]

It's not impossible the head is cracked but it is very unlikely if it has never over heated. I suggest you get the cheaper and more probable problems worked on first, before taking the head off. That means the thermostat and EGR cooler need to come off for examination and testing. (Test the thermostat by putting into boiling water.) If both are OK refit them and refill with coolant, ensuring you eliminate all air locks. Air locks can be very difficult to get rid of. I used to apply vacuum to expand any air to the reservoir, but I appreciate that few people have the ability to do so.

[Michael r]

Av tried to bleed the air lock out like it says via videos let it run with the tap open heat was coming through car got warmed up then put thr cap back on and heating went bwck to cold again av spent around700 on thr car now am just fed up with it 1 thing after another lol