Coolant Leak at Oil Filter Housing Console

Tom · #1

Last week I replaced the thermo switch in the radiator for the fans, and switched over to G48 coolant. When done, I pressure tested the system to 14psi and it held for an hour without a leak. Drove the car 10+ miles and all was well. Yesterday I noticed a few drops of coolant on the floor, so I thought maybe the radiator hose or something else I touched was leaking. I pressurized the system again to 14psi and got a fairly steady dribble of coolant under the car. I'm very mindful of leaks migrating and fooling you as to the source, so I'm not ready to concede the issue until I can spend more time investigating, but it sure seems to be spraying out under the #2 exhaust port -- and the only thing I can think of in that area is the block to head joint....

I've never seen or heard of an external coolant leak at the head gasket on a 944, but what else could cause this:

If you can't see the water spraying out, click on the gear icon at the bottom of the video and select 1080p resolution -- it's clear as day in high resolution and nearly invisible in low resolution....

Dare · #2

Yikes! No chance its coming from the elbow hose that goes from the heater hard-line to the water pump?

What type of head gasket? Maybe the pressure test pushed the gasket out?

Tom · #3

Dare wrote: Sat Dec 20, 2025 9:14 pm Yikes! No chance its coming from the elbow hose that goes from the heater hard-line to the water pump?

What type of head gasket? Maybe the pressure test pushed the gasket out?

I'll snake a camera down there tomorrow, and hopefully capture it spraying out of it's source. But it's literally spraying out right under the #2 header -- which makes me think the HG. Holding out hope I'm wrong...

Tom · #4

So I "thought" I'd sleep better if I got the endoscope out and had a look. Not so much though.

After pressurizing to 14psi, coolant is just squirting right out between the head and block.

Will need to sleep on next steps -- slap a new HG in there, rebuild the original 2.5, finish the monster 3L I started years ago.... or a gallon of Stop Leak maybe.

t36 · #5

Bummer!! All of this after your dedicated flushing!!

Dare · #6

Tom wrote: Sat Dec 20, 2025 10:18 pm After pressurizing to 14psi, coolant is just squirting right out between the head and block. Will need to sleep on next steps -- slap a new HG in there, rebuild the original 2.5, finish the monster 3L I started years ago.... or a gallon of Stop Leak maybe.

Booo! Sorry to hear that. What a weird failure. How old is the existing HG?

Tom · #7

t36 wrote: Sun Dec 21, 2025 7:13 am Bummer!! All of this after your dedicated flushing!!

Yeah, I can't come up with a compelling reason to link the recent coolant work and this leak, but a pure coincidence? Wonder if the g48 is harder on seals, or maybe it's been on the brink for a while and pressure testing did it in, or the Porsche gods just want me to rebuild the original motor finally...

t36 · #8

I would think it’s just annoying coincidence!
But selfishly - if you do a motor rebuild I’m sure it would result in a lot of really useful documentation for the rest of us in true Tom Carpokes style.

whalenlg · #9

And I thought this kind of thing only happens to mortals like me!

Happy to come by and help when you get started - let’s of free time starting mid Jan.

PSU_Crash · #10

Oof... hate to see that Tom! Perhaps Krampus came early this year. I don't believe in coincidence, but I'm not sure what makes sense there.
Years ago I had a similar issue, although with a new build, where one of the alignment dowels was holding the head up ever so slightly. Compression and leak down looked good, then when at temp it would weep. Not your situation this time, unfortunately.
Like t36 said, we all look forward to your detailed tear down and rebuild report