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Old 09-10-2009, 11:06 PM   #1
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Failsafe thermostat?

OK, basically I put in a 180 failsafe thermostat because it was running a little hot. It turns out I had a bad waterpump and mud in radiator fins and it did overheat. Fixed those things plus put on new fan clutch and hoses and put in a new 195 thermostat. I purchased another failsafe thinking that is the best. I put in coolant but didn't "burp" the air out and it warmed a little past 210 on the first drive. Let it cool and put in more coolant. This time it was slow to heat up. I fear this 195 failsafe thermostat has locked itself open because the temp got up to roughly 215-220 on that first ride.

Now I have to take it apart again. I read on another forum these failsafes are locking open at temps that are really not overheating and giving other people problems. If I find this one has locked open I'm going to have Autozone replace it with a normal thermostat and give me a new gasket.

Anybody else have issues with the "failsafe" thermostats?
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Old 09-11-2009, 09:07 AM   #2

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Did you get all the air out? So we can understand a bit more.. what is the temp its running at right now?

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Old 09-11-2009, 09:04 PM   #3
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Nothing wrong with the cooling system, just these failsafe thermostats are for the birds.

This is what NAPA says about them and I agree - NAPA Heating/Cooling

I bet I only got to 220 because of a little air (in less than 5 miles driving), topped off with coolant, then it wouldn't heat up quickly. I guessed right, took it apart and 2nd one stuck open. These things are junk. A Jeep can easily get to 215 or 220 on occasion and not really have anything wrong (mudding, AC running, hot days, towing, etc.) That I do not consider overheating and these failsafe thermostats should not open and clip open permanently at that temperature.

Took two back to autozone and since I had receipts they covered them and gaskets and they are not cheap $14 ea. plus gaskets $4 each. Still a pain to take apart, lose some coolant, refill, scrape off old gasket, wait for new gasket goop to cure, etc.
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Old 09-14-2009, 10:16 AM   #4
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i put a failsafe in and it failed open within one day. i had some garbage in my radiator so i just assumed that was the cause. im running a regular ol cheepy now (180).....
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.
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Old 09-14-2009, 10:33 AM   #5
Knows a couple things...

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A thermonstat that fails in the open position will NEVER cause the engine to run hotter. Failing open will only cause the engine to take longer to warm up. Better quality thermostats are designed in such a way that if they do fail, they'll fail in the open position to prevent it from causing the engine to overheat. I'm with the others thinking your cooling system may now have air in it so it just needs to be burped of all the air. Do a search using Google on coolant system burping techniques and you'll figure out how to burp it of any remaining air bubbles.
When you have a choice, buy American.
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