Blown Head Gasket — Bubbling.

[Trudant]

Compression test:
- US Passenger side (4,5,6) all show 180 psi.
- US Driver Side (1,2,3) show 60 psi, 60 psi, 100 psi.

The coolant is under pressure because of the air forced into the coolant lines During the test.

So I peeked inside with a borescope. I can see fluid in the cylinders and bubbling at the head gasket inside cylinders 1,2,3.

Should I just go all in on a head gasket replacement or should I be looking for a crack somewhere?

No white or smokey exhaust. Just light coolant smell.

Thanks!

[Trudant]

A little background on how we got here.

Car is new to me. 62k mi, 1999 model year.

Looks like someone forgot to install a gasket on the thermostat. I've replaced that and the water pump and didn't realize there was a head gasket leak until I got everything up and running with new coolant. I suspect the car overheated and caused this mess.


I've attached a picture from the borescope results referenced from the last message. The is from the first cylinder. Bubbling is at the seam between valves and cylinder wall.

[78F350]

While you wait for someone who knows more than me to reply, check out Hoffman Machine's web page. There's some good info about cracked heads and repairs. https://hamheads.com/2017/01/16/986-996-porsche-cylinderhead-cracks-explained/

I'm not saying it's not the head gasket. I just know that cracked heads are a much more common cause in these cars.

[Trudant]

Originally Posted by 78F350

While you wait for someone who knows more than me to reply, check out Hoffman Machine's web page. There's some good info about cracked heads and repairs. https://hamheads.com/2017/01/16/986-996-porsche-cylinderhead-cracks-explained/

I'm not saying it's not the head gasket. I just know that cracked heads are a much more common cause in these cars.

Totally agree. Head gaskets usually don't leak on these cars. That said... this one is?!

I've done my homework... and I can convince myself that several scenarios are possible:
1. Did something crack and then loosen things up enough to create a head gasket leak?
2. Could the head gasket leak have reduced pressure and prevented a crack from forming?


Trying to figure out the best path to a solution. May contact Hoffman and see what they say if there is no great suggestions here!

[Gilles]

Originally Posted by Trudant

May contact Hoffman and see what they say if there is no great suggestions here!

Les Hoffmann is a sure path, he would be able to properly inspect your head (and repair it) if you have a crack.