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Gregarious · Joined: 13 Sep 2003 Posts: 86 Location: Los Angeles

Guys, an unusual problem. At least to me it is. My car is devouring coolant! I just had the water pump replaced, so is it possible that it could be that, even tho the oil level seems to be unchanged? Or, like someone else noticed, it seems to be overheating even tho the gauge says normal. So perhaps it is boiling out? I am using the Water Wetter, and that seems to be doing great, but the overheating, and not the gauge, says it isn't doing THAT good. I am perplexed. ;D

Racing · Joined: 27 Apr 2004 Posts: 374

You need to performa a so called leak down test.
By pressurizing each cylinder-one at a time-you will first of all get a status of how each cyl is doing and what´s more if for instance the head gasket is AWOL you´ll clearly see this by the bubbles in the water reservoir.

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Just curious; on what do you base the statement that it is overheating, even though the gauge says normal? These gauges aren't "calibrated" per-se, so I wouldn't put a great deal of faith in the fact that simply because it is in the red it is overheated - or vice versa. The sending unit could be on it's way out, or an electrical problem (ground, bad wiring) could also be contributing to inaccurate readings.

The coolant loss could be attributed to your recent pump replacement and system refill. If you didn't get it "completely right", then over time the level will drop as the bubbles work their way out of the engine, being replaced by coolant from the overflow tank. Certainly if the tank goes empty - or nearly so - and you keep refilling it, and it keeps emptying , I'd agree there is definately a problem.

It's also possible that you have a small leak/seepage somewhere that is evaporating/boiling off before it puddles. Any "sweet smell" of the coolant as it might be dripping onto a hot engine component?

A leaking head gasket will more times than not show itself by white billowing smoke in your exhaust, oil in the coolant (thick film in the overflow tank) or coolant in the oil (milky looking oil).
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'79 Eurospec 931

Gregarious · Joined: 13 Sep 2003 Posts: 86 Location: Los Angeles

I get the idea it is overheating because it starts to boil and steam starts escaping. I get no oil in coolant or in oil. I like the idea of a pressure test on individual cylinders. We will see. Thanx. ;D
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Gregarious · Joined: 13 Sep 2003 Posts: 86 Location: Los Angeles

I meant I get no WATER in the oil, or vice versa.

924guy · Posted: Sat May 29, 2004 12:38 am Post subject:

id run it a bit, get it nice and hot, then pop the hood and look for steam trails, vapour, or any sign of a leak with a strong flashlight. you could have a pin hole leak someplace thats simply boiling out before its readily aparent. also check to see if theres a difference with the heat on or off... could be the heater core , they can leak down under the rug where its not noticable..though you should smell the coolant.. also make sure the system is properly bled and topped off , the internal pressure will be higher and hopefully force the coolant out of the leak more rapidly making the trouble easier to find...
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78 924
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CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

On the potential overheating issue... just asking ... has the thermostat been replaced in recent memory? Is the overflow tank cap on really tight? Has it been replaced recently? (it also has a pressure relief valve in it)
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'79 Eurospec 931

Tigger937 · Posted: Sat May 29, 2004 9:09 am Post subject:

I think I've seen this problem before and the news was not very good sad to say.

These aluminum heads are very sensitive to overheating and will warp easily if overheated. I have to ask, did the car overheat at any time with the old waterpump? If there was overheating, chances are probably pretty good you have pressure leaking from the combustion chamber over the head gasket into the cooling jackets at the head to block mating surface. What happens is the cylinder head warps and lifts up slightly near the #2 & #3 cylinder. The head gasket may or may not be blown, but when disassembled, discoloration can be seen in the head gasket where the leak was. Also, if antifreeze is getting into one of the cylinders, you will notice the exhaust valve for that cylinder has a whitish appearance compared to the darker appearance of the other valves.

A symptom of a warped cylinder head can be over-pressure in the coolant overflow tank indicated by a bloating of the plastic tank. It can actually expand like a balloon. Let the car idle, watch for proper functioning of the cooling fans and keep an eye on the overflow tank cap area........if it pressurizes due to this problem, the cap area will rise significantly as the tank expands. There can also be coolant leaking around the cap area from the excessive pressure. Like Racing mentioned in an earlier post, you can verify cylinder leakage with a leakdown test.

One other question, was the system properly bled following the changing of the waterpump?

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Is your fan kicking on??

-nick

numbbers · Posted: Thu Jun 03, 2004 9:40 am Post subject:

OK, coolant disapearing, but no foamy oil. Car boils over. You have a blown headgasket. Do a compression check to verify.
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wdb · Joined: 02 Nov 2002 Posts: 2024

I second numbers diagnosis . some of these heads are required to be retorqued , I think every 30K . I would try retorqueing the head bolts and see if that fixes the problem . it only takes a few minutes, so its worth a shot .

Gregarious · Joined: 13 Sep 2003 Posts: 86 Location: Los Angeles

I pulled the head, sent it out to check for warping, and it was OK. Oh, and first we tried retorquing like you said. No go. While it was in the shop, I had the valves redone. That head gasket is expensive, but it works fine now. I learned how to bleed the air from coolant at the elbow screw, and the overflow tank is new. No probs with that now. Thanx guys.

scotchw · Joined: 14 Aug 2005 Posts: 30 Location: Basingstoke, UK

Thanks for the info in this thread guys. The comments Tigger made apply to my car unfortunately - especially the bloated exp tank

I've been chasing coolant leaks ever since I had the car, & several hoses have swollen/split & burst. I'd put it down to 25 yr-old hoses & me pushing a car that had been stored for pretty much 14 yrs back into daily commuting.

But I've had a little bit of mayo in the engine breather hoses/oil separator, very occasional burst of "steamy exhaust" during engine warm-up & [the main thing] repeated air locks in the cooling system - I am always bleeding this cooling system!!

I'd suspected head gasket issues, but kept hoping it would be simple things... but no - new head gasket set + head bolts arriving tomorrow.

Will a regular compression test show which cylinder is leaking? Or does it need a leak-down test? I suspect it might be a warping head issue, because the coolant pressurisation only occurs on highway journeys - I ran it for 10 mins on the drive at 2K rpm (to bleed coolant system) & tank did not bloat up.
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'82MY 924 Turbo Euro RHD

Smoothie · Posted: Wed Oct 04, 2006 6:39 am Post subject:

No need to do an actual leakdown test - just need to find a way to hook-up a pressurized air source to the cylinders. One way of course is with a leakdown tester, but some compression testers have quick disconnect fittings of the same type used with air compressors that may plug right in if you have a compressor with the same fittings.
You'd have the cylinder to be tested at TDC so the valves are closed, pump in air and look/listen for air bubbles in the coolant.

Depending on your climate, your engine will be more or less prone to collecting internal condensation and the mayo in the breather system is caused by that plus deficiencies in the earlier versions of the 931 breather system.
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-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

In my experience a plain old compression test won't always show much of a drop on a cylinder that has blown the through the gasket.

When you get your steamy exhaust at startup, quickly shut it down and pull the spark plugs out. You'll get smoke pouring out of one of the plug holes - which would be the cylinder where the gasket break is. I'll bet you a nickle it will be #4

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1980 931S
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