My wife was driving her 96 OBW on the interstate the other day. Coolant was leaking, blowing all over and the car overheated. Couldn't find any splits in any hoses. Top radiator hose was colapsed. Coolant resovoir was overflowing. When I got there, big puddle under the car. Very little coolant in radiator.

 

Had it towed to shop. They put some coolant in it to drive it to the bay. So far they can't find a leak. Was concerend a month or so ago about a HG leak. They did a leakdown and hydrocarbon test. Negative. I did an oil analysis, also negative.

 

Any ideas what pushed the coolant out or how it got out?

The sort of HG leak most Sube engines develop is the sign of a high-quality gasket, and head-to-block design. I know it sounds stupid.

 

The leak is TINY, and it's compression/exhuast gas moving from the cumbustion chamber into the coolant passage. This will slowly force coolant backwards out of the system, via the overflow tank.

 

Under some circumstances, where the engine is worked hard and then suddenly allowed to relax (coming off a highway) the engine will overheat abruptly due to vapour lock in the water pump. All the tiny bubbles of compression/exhaust gas that have seeped into the coolant, collect in the water pump, and due to the pressure drop across it, expand and leave the impeller running in a big gas bubble.

 

Hydrocarbons should really be present in the coolant, but if only exhaust is making across the leak, there will be CO and CO2.

Thanks for the reply. She said she was going fast when this happened. 85+, keeping up with the flow. No letoff on the engine at all.

 

The shop is doing another hot and cold compression test as well as hydrocarbon test.

 

John

and be unable to locate a small intermittant Head Gasket leak on a Subaru.

I always thought the HC test would find it but apparently it does not always show up untill it gets pretty bad.

Tiny head gasket leaks have always been a pain on any engine.

so do you just live with them until they go? or would you replace it now?

well, if its still blowing coolant all over and overheating like you stated previously, i'd probably get her fixed..

Well, if you trust everyone who drives the car to keep a very watchful eye on the temp gauge - every two seconds or so - then you can leave it a bit, while you save up the money.

If you can't be sure that it won't be allowed to really overheat and warp the heads and seize the psitons...change the HG's now.

Oil seals, cambelt and so on would be good to include....

So far the guys at the shop have been unable to get it to repeat itself. One of the mechanics lives about 40 minutes away and he's going to be driving it back and forth. They did another leakdown and sniffer test in the radiator and they were both negative. They are thinking it's the thermostat possibly. Going to replace it and the hoses while they're at it.

 

 

I'm wondering if the block heater may have some corrosion on it and it's blocking a coolant passage?

while doing major engine work so a thermostat is a good start.

The hoses should show up in a pressure test if they are the problem, but if old change em.

I don't live in engine heater land anymore but never saw a problem other than a kinked hose when I did.

Pop the radiator out and have it cleaned and inspected while you are doing the hoses and thermostat and get on good terms with your personal God.

I suspect in the end you will have to change the gaskets but we can all hope.

Looks like it's either the HG or a cracked head. The mechanic drove it home and it did fine, but when he drove it in this am it did the same thing. So they're removing the heads. Going to have them pressure checked. Replace the HG's and Machine the heads. If they're cracked we'll have to get new ones.

 

Anybody have any idea what a new set of complete heads costs?

 

John