Case of the missing coolant

[BennSport]

I started my car up the other day after letting it sit for a couple weeks to find that the fans were kicking on more frequently than usual. Pop the hood only to find my reservoir completely empty. No coolant leaks under the car, and no dried up coolant on the underside of the bay to signify any leaks. Put more coolant in the car and in the long process of bleeding it (which is another issue I need to figure out) but I’m perplexed as to what could’ve happened. Any ideas?

[New2me944]

What is your oil level, and how does the oil look onthe dipstick?

[whalenlg]

Any unusual smoke out the tailpipe?

Did you check the oil for signs of coolant mixing?

Those would point to a head gasket failure.

If no to both, then I would try a coolant presure test and look for leaks.

[t36]

Pressure tester time!
If no puddle, it could also at the back of the head dripping on the bell housing . A lot can collect there before dripping.

[PSU_Crash]

After having mine all apart and bleeding the system I didn't get that bleeder screw tight. It leaked just enough for me to notice the coolant level dropped by about half over 500ish miles. Never left a drop on the floor. A little snug up and good as new. Loose as it was I'm surprised it didn't leak more.

As for the bleeding process. Just fill it up and crack the bleeder while it's running. Once you are up to temp and the bubbles stop, you're done! I have also seen people put a fitting in the bleeder screw and run a clear hose back to the resevoir. Less mess, same idea.

[Tom]

Chances are you have a tiny external leak that just steams out coolant without ever dripping. I second (third?) the pressure test suggestions. Pump up the system to 10-14psi and let it sit 15 minutes or more. If you get drops, you can then work backwards to find the source. Truly no better way to find sneaky leaks. If you get no drops anywhere (and don't have damp carpet or the smell of coolant in the cabin), then consider the possibility of mixing from the oil filter console or head gasket. Look for mocha sludge in the oil cap, oily crud in the coolant reservoir, unexplained high oil level, streaky oil when drained, coolant overflow after hard driving, one or two steam-cleaned spark plugs, etc.

But hopefully it's just a sneaky leak. I used a pressure with an inflatable bladder for years, but after it failed beyond all patch jobs, I stumbled on to this one, OEMTOOLS 27069. It fits right on the 944 reservoir and comes in a nice compact case without all the endless/unneeded adapters in the other kits. The bonus of this one is that it seals below the overflow port, so you don't need to pinch off the overflow tube. If you own a 944, a good pressure tester is a must-have tool.

pressure-tester.jpg (117.88 KiB) Viewed 282 times

[BennSport]

I’ll go in and check the oil in the cap at some point today, although I did check my oil level and it didn’t seem to rise. @PSU_Crash, how tight did you get your bleeder screw? I snugged mine up but I’ve always had issues venting all the air out of my system.

[gb951]

Chances are you have a tiny external leak that just steams out coolant without ever dripping. I second (third?) the pressure test suggestions. Pump up the system to 10-14psi and let it sit 15 minutes or more. If you get drops, you can then work backwards to find the source. Truly no better way to find sneaky leaks. If you get no drops anywhere (and don't have damp carpet or the smell of coolant in the cabin), then consider the possibility of mixing from the oil filter console or head gasket. Look for mocha sludge in the oil cap, oily crud in the coolant reservoir, unexplained high oil level, streaky oil when drained, coolant overflow after hard driving, one or two steam-cleaned spark plugs, etc.

But hopefully it's just a sneaky leak. I used a pressure with an inflatable bladder for years, but after it failed beyond all patch jobs, I stumbled on to this one, OEMTOOLS 27069. It fits right on the 944 reservoir and comes in a nice compact case without all the endless/unneeded adapters in the other kits. The bonus of this one is that it seals below the overflow port, so you don't need to pinch off the overflow tube. If you own a 944, a good pressure tester is a must-have tool.


pressure-tester.jpg

Or, if you are a cheap b**t*rd like me, check with you local auto parts chain, they may have one for *free* rent... as long as you return it and get your deposit back.

[PSU_Crash]

I’ll go in and check the oil in the cap at some point today, although I did check my oil level and it didn’t seem to rise. @PSU_Crash, how tight did you get your bleeder screw? I snugged mine up but I’ve always had issues venting all the air out of my system.

I put a new crush washer on it and used a 1/4" ratchet. Holding the ratchet head in my palm and about as tight as I could. So not super tight. It was obvious when mine was leaking ... once I looked. Wet all around it and a little bubbling when running.

[BennSport]

I’m using a combo wrench and snugging it up pretty well so I shouldn’t be busing any issues. When I replaced the bleeder screw and crush washer recently, I applied some non hardening sealant to both faces of the washer. That seemed to help at first, but now when I vent the system it seems like some of the sealant is coming up with the coolant that bubbles out.