Sadly I also have a Q5 2.0 tdi , (2011) as well as the NC1. I have a very odd issue with the engine consuming / leaking coolant and wondered if anyone out there has any suggestions?
Started off just loosing fluid randomly. No overheating. Would hold pressure for days after switching off. Replaced header tank and filler cap. Then it started pressurising the expansion tank and blowing off the hoses on the top of said tank. Replaced water pump and cam-belt as well overdue anyway. Great result, no more pressurisation.
But it seems to want to sit at below min on the level on the tank. It was below MIN and I drove 100 + miles in one trip + shorter journeys and it never lost any coolant. But when I filled it to between MIN and MAX and did a couple of short tripsâŚ.hey presto back below MIN again. It canât âwantâ to sit at a particular level surely?
I monitored the ECT, (Engine coolant Temperature) using OBD11 in Live Data mode and it varies between 70-78 degrees never gets to 80+ where the stat is supposed to open?
Any ideas gratefully received. Thanks for taking the time to read.
With this being an Mx-5 forum NOT Audi, youâd get a better chance of any kind of related reply on and Audi, surely.
Or am I wildly oversimplifying this ???
but lots of people on here with mech and engineering skillsâŚ..and many do have experience of other cars, so just thought Iâd ask. Hence not posted in the technical MX-5 area. regards, Marc
If your Audi Q5 2.0 TDI (specifically the common EA288 engine) is building excessive pressure in the expansion tank, it often indicates that combustion gases or excessive heat are entering the cooling system
Common Causes
Blown Head Gasket: This is a frequent culprit. Combustion gases leak into the coolant channels, over-pressurising the system and often blowing coolant out of the overflow valve.
Faulty EGR Cooler: An internal leak in the EGR cooler can allow high-pressure exhaust gases to enter the cooling system, mimicking head gasket failure symptoms.
Switchable Water Pump Failure: The 2.0 TDI often uses a switchable water pump with a shroud that can get stuck. If it fails to retract, the coolant doesnât circulate properly, leading to localised boiling and pressure build-up.
Leaking Intake Manifold (Intercooler): On some 2.0 TDI engines (like the CNHA), the intake manifold contains an internal intercooler. If this leaks, it can cause internal coolant loss or pressurisation.
Blocked Heater Matrix: A restricted heater matrix can limit flow, causing the coolant to overheat and âboil overâ back into the expansion tank, especially after DPF regenerations.
Recommended Diagnostics
Sniff Test (Combustion Leak Test): Use a chemical kit to check for CO2 in the expansion tank. If it changes colour, exhaust gases are entering the system (Head Gasket or EGR cooler).
System Pressure Test: Pressurise the cooling system with a hand pump to check for external leaks or internal drops.
Check Glow Plugs: White âsteam-cleanedâ spots on glow plugs or coolant deposits can pinpoint which cylinder has a leak.
Inspect Water Pump: Check the timing belt area for pink/red crusty deposits, which indicate a failing pump.
Thank you for the info, specifically the how to diagnose bits. The change of water pump seems to have cured the over pressure issue. itâs âjustâ the leak / loss now which is confusing the issue. Next step has been suggested as EGR valve but not cheap or easy and if itâs a head gasket??
thank you for your research though it all adds to the thought process.
Iâm glad the info was of help. It seems that the mods donât like us members to use AI generated advice, which I was unaware of. The naughty step beckons again.
AI can be a useful tool, but when forum threads are filled with generated answers, it creates ânoiseâ that makes it harder to find genuine, battle-tested advice. Letâs try and keep the quality high by sticking to human-to-human help.
I use AI for a few things and have found it quite useful. It does have limitations of course so a degree of caution is always required. I think most people understand that.
Thanks for all the info, no matter where from . I wouldnât trust AI for a medical diagnosis but youâd be surprised how close the NHS diagnostic tools are to âGoogle Answers Allâ
Regarding the heater, it did blow cold on one occasion when the pipe blew off and most of the coolant disappeared. Now fine and not over pressurising at all. ( since new water pump) Just seems to want to sit at below MIN on the header tank. No other symptoms at all now. Thanks again.
I thought the info sounded reasonable and worthy of consideration. The slightly low coolant level could possibly be an air lock somewhere? Happy to help.
I guess Iâve had a few occasions where, after a great deal of sweat, toil and blind alleys, someone says âoh you should have aske me, I had exactly the same and it was âŚâŚâŚ..â
I donât necessarily agree that AI had the answer and it definitely provides different results for subtly different questions so all input gratefully received.
. I wouldnât trust AI for a medical diagnosis but youâd be surprised how close the NHS diagnostic tools are to âGoogle Answers Allâ