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Mantonite

Weird Thermostat Replacement Issue

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This one has me baffled.

 

When I got the car, I was told it had a cooling problem so I ran without a thermostat, then a 180 deg one. After the recent cold snap, I decided to swap it out with a stock unit. I swapped it out and promptly overheated. I pulled it out to double check I didn't totally bonehead the install and it was fine. Tried again with the same results.

 

Put the old one back in, and we are fine. The only oddidity is the upper rad hose seems to be under a lot of pressure.

 

Bad new t-stat right??? Nope, passes the boiling water test without a problem.

 

The only thing that I can think of right now is a bad rad cap, but why would it be fine with the 180 deg one but not the 190?

 

I know these have finnicky cooling systems, but this is a bit over the top. HELP!

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check to see if the stat that works has a tiny hole in it to let air thru-and compare against the one that didnt work.

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did it overheat according to the gauge, or bubbles coming out of the overflow tank?

 

I'd highly recommend finding a cheap temperature gun and verifying that the dash gauge is correct/wrong.

 

My 88 GL reads a bit high, the 91 loyale barely registers, and the 85 turbo is just fine when it's in the red. bottom line - these gauges aren't very accurate.

 

a new/tested rad cap wouldn't be a bad idea either.

 

(I think www.tempgun.com has some for cheap?)

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Interesting thought on the gage, but why would it read fine with one and not with the other?

 

Just had a thought... what would happen if I missed the glycol/water mix? Could the high pressure/overheating be a boiling off effect?

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On another note, I once did a comparison between the OEM thermostat, and the "aftermarket" equivelent. Lets just say they don't stack up... neither do the gaskets. Start by getting a proper thermostat from the dealer so you know it's right.... don't have to scratch your head that way.

 

Maybe someone who saw the pics I posted about them can chime in here.

 

Maybe I just missed your return. In any case, welcome back GD.

 

Gosh - thanks guys!

 

GD

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The aftermarket ones just suck - they don't seal as well. You can RTV the crap out of them and make them work if you really want. I prefer the Subaru ones as they are metal with a rubber coating. Very nice.

 

GD

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New thought this morning... what is the boiling point of straight Glycol? I may have grabbed a bottle of straight stuff instead of the 50/50 I should be running (oops).

 

Maybe the low temp stat keeps it just below the boiling point of the current mix and the other puts it above???

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I have had good luck with Stant brand thermostats.

 

I have Run 100% glycol, 100% water, 50/50 normally(recomend that). Never noticed a difference in normal conditions.

 

Dave

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I use chevy small block thermostats. They are the same size (54 mm) without the jiggle pin. Drill two 1/8 inch holes opposite of each other and they work just fine.

 

Using chevy thermostats means all different types of temp ranges. I found thermostats from 155 degrees all the way up to 220 degrees

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Ethylene Glycol.

 

Why the holes torxxx, and what is the point of that jiggle pin anyway?

 

I believe the jiggle pin/extra holes allows air to pass through the thermostat, so when you do a flush & re-fill, it doesn't overheat due to a pocket of air before the thermostat opens.

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The other good thing about the jiggle pin is that you can tell if the coolant system is full without opening the cap. Checking the overflow bottle does not count. I blew the head gaskets once due to the bottle being full, and insufficient coolant in the engine / radiator.

 

When the eengine is cold, grab the upper radiator hose, and squeeze it. If the system is full, you should hear the pin jiggle. If there is a little air, you can hear the bubles. Bad low, you hear nothing, since air won't jiggle the pin.

 

Dave

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Bad low, you hear nothing, since air won't jiggle the pin.

 

Dave

 

On the subject of the jiggle pin, the FSM for the 88XT says the jiggle pin should be "pointing up" in the 1800 engine. Sounds confusing, which way do you guys install them?

:-\

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which way do you guys install them?

 

I go by the sensor. The cylindrical part with the wax pellet, surrounded by the spring. That part goes towords the engine / away from the radiator, opposite the direction of hot coolant. In other words, the sensor part has to be "facing" the flow of hot coolant where it exits the engine. On EA82s, the hot coolant exits via the intake manifold.

 

The cooling system has a path that lets some hot coolant from the block pass by the sensor, even when the thermostat is closed. (the 1/4" hose on EA82s) If the thermostat was installed backwards, the sensor would open way too late. Probably dead engine too late.

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