' 86 5000 csq avant oil pressure relief valve

[tom winter]

Hi all. I'm a new member. Totally blown away by the knowledge base here.
Very impressive and makes me feel very ignorant.

So, under the premise that no question is too stupid, here's mine.

I have a '86 5000 csq avant. The manifold cracked, so I tore 'er apart. In
the process, I noticed that the turbo was leaking oil, so I replaced that,
installed a K&N air filter, new gaskets, etc and bolted everything back
together again. 

The car drove and ran fine, for about 50 miles, then the radiator blew.

I think, but am not sure, that the failure was due to age. I was going about
65mph up a hill on the freeway, felt the car "cough" once and it was still
running fine, but of course the computer started flashing that I was out of
coolant and then the temp started going up. Fast.

No worries, there just happens to be an exit right where I need one, and
better yet a rest stop. Pull over. Get new radiator, install radiator in
true shade tree mechanic style, car starts right back up, but then I notice
it's leaking oil like a mother.

Had car towed back home, start to take off all the tin on the front around
timing belt, etc, and it appears now that I have all the oil cleaned up that
the leak was coming from the Oil pressure release valve, not the main seal
or anything like that.

Does this sound right? Would an old radiator blowing cause the oil pressure
to go crazy?

And, since my Bentley manual only shows the pressure valve in the schematics
with no commentary about it whatsoever, what's the fix? Replace it? Is it
supposed to re-set itself or is it a one-time ejaculation and is now dead?
Anything else I should look at or consider?

Thanks for any advice and help. One day I'll be as smart as the rest of you
guys!

Tom
5000csq avant with a leaky gut