Coolant leak (over pressuring)

[Puggie]

We needed a sensible family car, so bought a mad audi. 2 weeks later a lorry gave us a cuddle and wrote it off.
Bought another daft audi with engine trouble (dropped a cylinder) with the thought it could be an easy fix, if not we have a spare engine in the first car (oh how I laugh reading that thought process now). So that engine had a broken valve and scored bore so we swapped engine 1 into shell 2 and did a bit of preventative maintainance on the way (new ic cores, turbos rebuilt, new belts, bufkin pipe etc) and put all the best bits of the 2 cars on one. So just got it all done (literally taken years due to kids etc) sailed through its MOT, without issue.

And now I see we are losing coolant, which appears to be the head gasket of engine 1. We never really ran it enough in the 2 weeks it was on the road to find these issues. It used a little coolant, but I also found a split in the top of the rad, so assumed it was from there.

I could rebuild engine 2 but it will want liners fitting as the bore is scored, the head just needs a valve and a little dink welding in and a skim.

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[Puggie]

Very tempted to k-seal this one (it's a tiny leak) and rebuild engine 2 to swap in a few months time!

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[Shoppinit]

Don't think I could bring myself to put k-seal, rad-weld or similar in an RS6. Having said that, I guess it's only temporary until you can change the gasket. You don't want to make things worse and make things more difficult for yourself.

[chunky79]

Don't think I could bring myself to put k-seal, rad-weld or similar in an RS6. Having said that, I guess it's only temporary until you can change the gasket. You don't want to make things worse and make things more difficult for yourself.

Don't think I could do a bodge job, even if it's going to be temp. Some serious bad luck already.

[Puggie]

I have serious reservations, but someone already has (you can see where he tied his horse up while he did!),and that is the only reason I'm considering it. Its a small leak, the little manometer tube on the tester only glugged a bubble through every few seconds, it's quite a lot of pressure, but not much volume flow. I'm thinking along the lines of any damage is already done. And I have every intention to sort the head gaskets properly (not sure which engine to do it on though).

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[chunky79]

You tempted to do some upgrades if/when you pull again? Fingers crossed you can make a good one out of the 2 engines.

[Puggie]

Right, compression test showed (looking into the bay and measured in bar):

8.3. 8.9
8.3. 8.8
8.8. 8.7
8.3. 8.8

Looking at the piston tops, the 8.3s appear to have a small damp mark on the upper edge of the piston crown. I'm wondering if it has lifted a head at some point?

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[Shoppinit]

Compression should be 9.5:1

[Puggie]

This was just cranked on the starter and the throttle closed, that could leave them a bit low.

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[Shoppinit]

Why?

[bilko1]

There's a complete MTM spec engine for sale on eBay atm.

[Banana man]

I fitted a supposed good engine into my S4 from a “race engine builder” down south, seemed legit too, have a website and everything.

Anyway, the heads where already on but built the engine back up, had loads of invoices for internal work so (wrongly) assumes it would be fine, start driving it and exactly the same symptoms, we realise it’s head gasket related, mine is better when coasting, once boosting 25 psi it pressurises the system and I loose coolant.

Now due to not having time recently and shows I was attending I also needed to put a plaster on the problem and bought “steel seal” I think you’ll need 2 bottles and it’s not cheap, it didn’t fix the problem but it’s a lot lot better.

I’ve been gathering parts for the next engine removal to cure the problem but currently it’s ok to drive, I took it to C&M last weekend, and I was surprised that when I got back I still had a fair bit of coolant left even after some traffic light Grand Prix to clear the cobwebs out, it’s been in the coolant system for 12+ months, although how much is actually left I couldn’t say.