Yabo

Hey guys, I'm afraid I need some help.

I recently have done a head job on my 951 after it was overheating, losing coolant and maybe some mix in the oil, but not in the coolant. Had the head machined (a very good $$ job on it too).. Piston walls seemed OK, pistons all had similar minimal rock so the rings should be good enough. I also have done the waterpump, belts, hoses, replaced turbo waterpump, balance shaft seals, front engine reseal, and probably some other things I'm forgetting.

First start went ok, still seemed to get a little hot after idling for a bit. drove it up and down the block, no smoke, no smells, runs great but temp still high. I've had difficulties believing the temp gauge because it jumps around a lot and makes me think there's a bad ground anywhere. Also, the few times I ran it for 10-15 minutes I seemed to be losing some coolant but not visibly dripping anywhere.

Drove it for 15 minutes or so yesterday to finally see where I'm at, temp on the gauged stayed a little warm but reasonable until I got back and idled, I got out and looked underneath to see it start pissing coolant (seemed to be forcing itself out of the hose that goes from the metal crossover near the headlight bar to the tank), which the clamp was plenty tight on. On top of that, the oil (new clean oil) is foamy white (mixing) and was now leaking fast out of the cam tower shaft into the timing belt area (on my fresh belts.. ).

I guess my question here is, can the turbo leak coolant into the oil without leaking it into the intake, since there is no smoke? What are my other possibilities for mixing? I'm still holding out hope this is residual mix that was leftover somewhere in the pan that didn't drain when I began the work, but I'm doubtful. I'm also wondering if maybe the combination of being too hot, with water in the oil, could have caused the cam tower to leak, because it never leaked until this one drive.

I'm not that kind of guy (I can prove it by having my NA as a daily driver for 7 years) so it pains me to say this, but I may be near the tipping point of cutting my losses and moving on to something else...

Willard Bridgham 3

Have you had the turbo out and checked the seals? Oil and coolant are there, too.

Paulyy

i dont think the turbo can mix water with oil. the water passes through the chambers to cool the turbo only.

Yabo

I had the turbo out, because I found I couldn't get the balance shaft cover off (which I had already loosened) without removing it. I did the exhaust and orings involved with removing it, shaft felt pretty snug so for now I didn't get it rebuilt. I hadn't heard of coolant and oil mixing in the turbo but I would like to know if it could happen, or how else this could happen.

You can't get oil coolant mix from the oil cooler since it's external, unlike the 944, right?

Tedro951

I vote for oil cooler seals.

lart951

That will explain the milkshake but what about the overheating.

Maybe you need to purge the cooling system or the worst a cracked cyl wall.

ChrisJ951

I had a cracked cylinder wall in my car and it wouldn't overheat but the temp gauge would rise to just under the red zone before the fans kicked on or I started moving.

Yabo

Yes, you see my dilemma.. Maybe there is enough coolant in the oil (from losing coolant during my few idling sessions over the past few weeks) that its not cooling correctly? Seems unlikely.

Cylinder wall crack seems a bit unlikely as theres no smoking, can't feel any pressure with my hand over the coolant reservoir (with the cap off, cold engine, obviously cant try it with boost that way!). Or am I off base with that assumption?

Its a new thermostat, but I guess I should pull that and try it without. Also, I pressed the AC switch to make sure the cooling fans were on, and it still overheated. I worry about a bad out of the box waterpump, however rare that is. Not sure how I would check that.

BTW, temp would come down pretty significantly when I revved the engine, (from upper white line to below 1/2, almost to 1 white), even after bleeding it a lot.

I think my action path probably needs to be, 1. oil cooler seals, 2. another fresh oil change, 3. remove thermostat and then see how it goes? Maybe my radiator is plugged up?

Yabo

Err.. what else would happen? Mixing? how did you find out it was cracked, just happened to tear it down because of the temp issue?

Tom M'Guinn

When the coolant leaks into the oil, eventually air or oil take it's place, leading to overheating.... Can't say for sure, but might be worth reading up on oil seal replacements here:

http://members.rennlist.com/tom86951..._seal_repl.htm

Tedro951

I was thinking he mentioned that he doesn't trust the gauge.

If it was mine, I'd do the $5.00/5 minute test for combustion gasses, then go from there.

ChrisJ951

After adding some mods the headgasket blew during road tuning exposing the cracked block after the head was removed.. Jury is still out if it happened during tuning or due to being a very low miles car that spent 25 years in Maine. (timing was not messed with and there was no detonation evidence on the pistons).

jerome951

Make sure you cooling system is completely bled before worrying about overheating. Usually takes a time or 2.

User 52121

^^^ This is exactly what I was going to reference. If your temp gauge is very quickly jumping up and down, it sounds like your cooling system hasn't been bled enough. They can be a big PITA to bleed ALL the air out of. Bleed it, then bleed it again, then just when you think you're done, bleed it some more. Before I had the steam vent kit, it took me probably a week of regular driving (bleeding after each shutdown) to get ALL the air out of the system.

That doesn't explain the milkshake though.

carlege

Since you did the head job what condition was the gasket in? Also as mentioned a combustion gas test kit is a great little thing to have. mine cost me $60. Not sure where you get one for $5