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Engine Overheating: Peanut butter coolant but clean oil

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Hello all, hope you're having a good night (or day)!

My '92 Loyale has run well for the past couple months I've owned it. No overheats, no stalling and good, smooth power (for a Loyale). A couple days ago I got bored and decided to drain and replace my coolant which was brown and a little chunky. I'm very very new to auto maintenance and I don't really have anyone to tell me what's what, so I didn't recognize the brown coloration as a sign of oil-coolant mixing. Drained it all out of the radiator and flushed with water till it came out clear, filled it up with new coolant and bubbled it for about 30 mins just like the YouTube videos said. Of note is that it didn't take all 6 qts of coolant like it's supposed to, only about 3. I chalked it up to some water from the flushing process staying in the block. Like I said, not very experienced. Car ran just fine for about two days until it overheated in the Chick-fil-A drive thru (best possible time, I know) and blew some white smoke out of the tailpipe. Of note is that my temperature gauge never went above about half, nowhere near the red. I went inside and ate my chicken sandwich and let it cool down. Coolant was back to that nasty brown although the level hadn't gone down, still right up to the fill cap. However, my oil was low beyond the dipstick. I had checked the oil a few days prior to changing the coolant and it was right where it should be. So I go to the Publix conveniently right next door and fill er up. Drove home (only about 2 miles) with no noticeable loss of power, but a steady rise in temperature. I thought at first that low oil might have caused the overheat, but it was still happening with oil full.

Did some research and found that burning coolant makes white smoke, and that that mainly results from blown head gaskets. But the thing is, the car hasn't blown any white smoke since that day at all. Not only that, but my oil is still clean, I haven't noticed any loss of power, and my radiator hoses are squishy while engine cold. Only the coolant is brown and contaminated. I think the issue may be combustion gas in the coolant system that's preventing my thermostat from opening and preventing me from adding the correct amount of coolant. What do ya'll think? Am I stupid and missing something obvious, because I wouldn't doubt it. 

I bought some pour-n-go head gasket sealer as a stopgap till I can take more drastic measures, but I don't really want to pour it in brown coolant until I know what the problem is.

Any advise would be greatly appreciated. Thanks in advance!

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What el freddo wrote. 


Don't bother with anything that claims it will fix it with a bottle of additive, it won't. 


Don't drive it any more, as you risk more fatal damage every time the gauge goes  above normal while low on coolant.   It does not need to get to red to cause trouble.


These cars have some peculiarities with cooling systems,  there are loads of threads about headgaskets on here.


White smoke only happens in some of the possible failure modes, and only when they are very well blown.

Mixed coolant in the oil I have had only one time with a very bad overheat, and no smoke of any kind.

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Don’t add the stop leak stuff.  It will not work.  

The symptoms don’t sound good but also you’re admittedly new and we only have what we can read to work with.  There’s a slim chance that you have something else going on and it’s not headgaskets. It seems ominous but It should be diagnosed for sure first. 

Oil loss could just be burning it internally.  

1. The brown could be internal scaling/rust and a quarter century of debris in the radiator and cooling system.  Overflow tanks alone can be filthy.  

The overheating could just be air still in the system. It never overheated and then overheats one time after you drained the coolant - the first step in that scenario is to make positively sure you got all the air out and there’s no leaks. 

The radiator cap - test it or install a new Subaru one.  

Thermostat - test or replace with a Subaru one.  You can boil it in a pot of water and see if it opens.

Radiator could be clogged. If the brown is debris then radiator may be internally clogged.  see if it can flow the garden hose turned all the way up from inlet to outlet. 

2. If it’s AT the trans fluid can also be pushed into the coolant via a failed radiator.  

It does sound like headgaskets could be the issue but make sure these simple things are ruled out first.   It being able to see it, it’s hard to say what’s happening with just text. 

Edited by idosubaru
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You covered alot of ground doing research thanks for doing that! :)

when you purge the air from the cooling system park on a steep incline like a hill, 4wheel up onto something or jack up the front end when idling to get the neck of the radiator higher than the heater core which sits slightly higher in the dashboard and traps air stick a screw driver or use your hand to up the idle a little and hold it whike pumping the hose.

use only distilled water not garden hose or sink/tap because it boils the minerals which clogs eVeRyThInG and use only mixed Green coolant or make your own... which I myself have mistakenly bought full strength NEED TO ADD water... and the funny thing of it is I filled up the reservoir THEN read the label, about 3 weeks later pop the cap to scoope things out and I got splooge/grayish brown crud around the neck.

other than that yeah definetly could be a head gasket.

here's a link to my story->



Edited by Len Dawg
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