Too much pressure in coolant.

[Dan39]

Hi just bought myself a Audi A3 2009 1.9 tdi. First realised I had a problem about a week after I bought the car, I went up a steep hill for the first time and the low coolant light came on and told me to stop the car. I stopped and the expansion tank seemed empty. I carefully removed the lid and the coolant rushed back in to the tank. 
everything I read points to head gasket, gasses leaking into coolant. Bought myself compression tester. Engine cold all but one cylinder read 400Psi the other 350psi. Engine warm all read 400psi. Has anyone had any experience with this kind of issue?

 

[Magnet]

Hello Dan,

Simple things first:- try replacing the reservoir cap with a quality replacement.

Cylinder compression testing and possible head gasket failure? This test really isn’t the most informative of tests unless the head gasket has failed between two adjacent cylinders.

A more meaningful test would be to have a coolant pressure test done on the car. 

Trade seller or private sale? How was the car described? Even with a private sale, the car’s condition has to match the advertised condition. 

Kind regards,

Gareth. 

[Dan39]

Hi Gareth, thank you for taking the time to reply to my problem. The cap is just plastic, not a pressure cap. I’m not sure how replacing it could help. Just to confirm the tank ends up with too much pressure (gas or air collecting in the top of the tank and pushing the coolant down below the low level. I might be missing the point. 
I like the idea of pressure testing the coolant. I’ll have a look at getting one. That might shed some light on the situation. 
I bought it from an auction cheap so it’s all on my shoulders. I thought it only had a dead battery. Bought a new battery for it and all was great for the first few days. 
im quite happy spending time in the garage sorting problems. I’ve spent a lot of hobby time on cars over the years so I’m happy to roll my sleeves up and get my hands dirty. The most difficult thing for me is initial diagnosis. 
Kind regards 

Dan

[Magnet]

Hello Dan,

Thanks for coming back on this. Yes, the caps are plastic, unlike my when -I-had-hair period when they were metal. Plastic yes, but pressure cap yes. Issues there are usually associated with unexplained coolant loss, and in reality is unlikely to be the cause of your problem, but worth a cheap shot. 

Coolant pressure test:- Appreciating you like to do things yourself, and this really is to be applauded, but the economics in this case hangs on investing in the equipment which you may not use again, vs. paying to get the test done - with an input of the expertise and advice from those conducting the test for you. Obviously, a personal choice Dan. 

An additional bit of background:- Does the car overheat? 

Since you have invested in a diesel, it would probably be to your advantage to find a local trusted diesel specialist who would be handy as a point of reference. Apologies for boring those who might have read this many times before, but worth having a chat with your local taxi boys - they usually know who to go to, and to avoid, in the local diesel world since their living depends on such people. 

Auctions, eh! Well you win some, you lose some. More so of an issue now where owners sell their vehicles to the likes of I Buy Any Shed  etc. and all are destined for auctions. The favoured route to buying is often buying privately, where vehicles can be road tested before purchase. Very often not a lot more expensive than buying at auction where you have to pay additional ‘commission’ charges. 

Perhaps you could let us know how you get on Dan.

Kind regards,

Gareth.