I have an Audi A4 1.8T avant.

Recently I noticed brown crap in the coolant, so I flushed and refilled, only for it to happen again. So, I bought a new oil cooler and switched it out, and flushed again. No change.

So, from what I have read, it looks like a blown head gasket. I whipped the spark plugs and did some compression tests today and surprisingly, the compression is OK, but there was brown gunky fluid on some of the plugs (same stuff as in the coolant tank - no surprise).

I was quoted £450 for a basic head gasket change at the local garage. He warned me that it'd basically be pointless if I could not also find the cause of the issue, check all hoses etc for blockages and so on. My first guess would be the dodgy heater matrix which I now know could have contributed to this.

My question now is where to go from here. The car is old and not worth spending big bucks. I am willing to try a DIY head gasket job if it is worth it but I am concerned it would be pointless without having the head checked for warping, etc. I am not sure I want to pay to have something like that re-built or skimmed (though I do not know what that would cost) for a car I paid less than 1K for. Is it worth it? Or do I just call it a day and sell for spares?

Any thoughts would be appreciated. Cheers.