2009 Q5 - coolant loss.....

[Richard27638]

Pressure is supposed to build up. Coolant boils at higher pressure, so pressure build up is normal. Two possible causes. Head gasket gone. Coolant leak from hose or gasket under pressure.
Take to garage to pressure test coolant system.

[Expatscot]

Pressure is supposed to build up. Coolant boils at higher pressure, so pressure build up is normal. Two possible causes. Head gasket gone. Coolant leak from hose or gasket under pressure.
Take to garage to pressure test coolant system.

My bad, thought it was a sealed system and somehow extra pressure was getting in...

Shouldn't be head gasket - just had complete engine rebuild so that was all replaced. Bottom end of engine was in great shape - the head was sent off, rebuilt, refitted, new cams, new water pump, new belt etc.

I was wondering if this would go back to micro-cracks in engine somewhere - not coolant to oil (that doesn't seem an issue) but allowing extra air in..... hence the pressure release. I had hoped had moved passed tiny crack in head opening under heat/pressure ..

Think will see a non-dealer Audi specialist before I give up - but after new clutch and DMF last August, then 5 months off road from November whilst engine was rebuilt (with string of delays) and now this... there has been £3K put into this in last 12 months so not wanting to have to bin it now.

[Richard27638]

Why was engine rebuilt? If coolant loss was not an issue before rebuild then rebuild was not correct. Somewhere something has been incorrectly fitted.

[Expatscot]

Why was engine rebuilt? If coolant loss was not an issue before rebuild then rebuild was not correct. Somewhere something has been incorrectly fitted.

Water pump went Nov 2021, which took out cambelt - which, well you know....

The damage was minimal and had just had clutch and flywheel replaced hence opting to repair.

Got the car back finally after various delays end of March 2022. The rebuild itself seemed then, and still seems now, fine in and of itself. I used the vehicle for work a couple of times. Will have put approx 500 miles on it.... then the mystery coolant issue started.

[Crasher]

Was the cylinder head skimmed?

[Richard27638]

In light of the work done I would go back to the garage who did the work. At a guess maybe water pump gasket or nearby hose leaking under pressure. If the cylinder head has been off the problem could be there. Bolts could have loosened off during first 500 miles after rebuild.

[Expatscot]

Was the cylinder head skimmed?

I am going to speak to Redman's Engine Centre tomorrow.... for ease of mind and helping work out where I go with this next I want to know 1. did they pressure test it before work carried out? 2. what you asked - did they skim head.

This has all been such a convoluted mess of a job with the delays and break down in comms between mechanic (lives round corner from me) and then me playing pig in the middle and sending the head off to Redmans, it coming back etc.

My mechanic didn't pressure test it before it went off, assumed they would.... I imagine they would to be honest. They are a large professional firm and this sort of thing is what they do... their bread and butter.

The coolant is definitely coming out into the engine bay, from somewhere near the expansion tank - seems to be at the back of the expansion tank where it sits near the bulkhead - that heat proof thick fibre coating I noticed was sodden with coolant after last test drive.

would the old micro-crack in the head that had been missed - cause this coolant loss out into the engine bay by expansion tank? There seems to be no sign of coolant/oil getting mixed, no mayo emulsion, dodgy exhaust emissions etc

[Expatscot]

In light of the work done I would go back to the garage who did the work. At a guess maybe water pump gasket or nearby hose leaking under pressure. If the cylinder head has been off the problem could be there. Bolts could have loosened off during first 500 miles after rebuild.

Not a garage as such - he is a friend, lives round the corner, used to have his own full workshop but now does so much other work he gave that up. He does homers for smaller jobs, and uses the workshop of a friend (another mechanic) with ramps if he needs to do anything bigger. It has been back round to him.. we have changed the oil cooler, the expansion bottle, and the pressure cap latterly.

There was link I posted to a possible 'hidden' leak of coolant from EGR cooler - but that is apparently in different area of the engine. This is coming out around expansion bottle, the rear of it I would say, comes out under pressure/sprays... but not under idle - only when being driven.

[Richard27638]

OK. Still likely to be linked to previous work. Does coolant temp stay normal until loss, or does it go above normal then lose fluid? Excess heat = fluid loss. Many causes.....

[Expatscot]

OK. Still likely to be linked to previous work. Does coolant temp stay normal until loss, or does it go above normal then lose fluid? Excess heat = fluid loss. Many causes.....

Temp gauge stays fine.... no rise from it.

No heat comes through into the cabin though - or very very occasionally it does. I have the blowers up full and on hot, all that's comes through is whatever the outside air temp is.

I am likely going to try an Audi specialist (not main dealer) locally for second opinion - depending on what Redman Engine Centre say when I speak to them.

I am loathe to scrap it... this issue aside it is lovely condition and has been serviced 4-5 times a year, just had new clutch/DMF a few months before it ended up offroad. BUT I need to stop using my nicer (once nice anyway) car for work - so I either get this sorted with a bit more £ or I buy another cheap car to use for work - and I know the history of this Q5 and its other new parts so would rather put the £ into this... (but even I at some point must admit defeat).