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Old 01-31-2012
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94 explorer coolant problems

I hate to start a new thread since there is a similar one in recent history, but here goes.

From the beginning... I bought a 94 explorer a few months ago with unknown mileage. It ran great but had minor fluctuation in coolant temp gauge. The radiator had a minor leak, so I replaced it, with a new cap and thermostat too. The coolant was nasty and neglected, I would guess it had stop leak in it as well.

I drove the truck from Oregon to Louisiana, ran great. Drove it around there at work for two weeks, no problems. After my two week shift I was driving to new Orleans and the coolant temp read high. I stopped and smelled coolant, shut it off. It was steaming from what appeared to be the water pump or heater hose. As it was dark and I had to catch a flight, I had it towed back to work and caught my plane to Oregon. I returned to work with a new water pump, heater control valve, all new hoses, new belt and tentioner. I replaced everything one night after work, saw no signs if obvious leaks. Poured coolant in and it poured right back out from the passeneger side under the valve cover, where the head meets the lower intake manifold.

A few weeks pass, I return to work this time with lower and upper intake manifold gaskets and valve cover gaskets. I pushed the truck into the hanger again after work one night and spent about six hours tearing the upper end of the engine off. The gasket blew out around the front coolant port on the right side of the lower intake manifold gasket. Good, here is the source. The next day after work I put everything together and fill up the coolant and run it. I had a hell of a time getting the air out, but eventually do. The truck runs great. No leaks other than a seep from a freeze plug.

But now the coolant temp gauge goes up to the "A" on normal (a bit high compared to my other 4.0s) during the first drive after starting it. It holds there for about 30 seconds, then drops well below the halfway point. Most days it fluctuates back and forth a fair amount. I replaced the coolant temp sending unit on top of the manifold, no change.

I'm kind of at a loss. After the problems that I dealt with, I'm worried about it running hot for that initial warm up. It did this a little with the old thermostat, though not as warm, and does with the new thermostat. Virtually everything else has been replaced it seems. Coolant is flowing well, I put a couple hundred miles on it and it isn't consuming coolant that I can tell. Could the thermostat be backwards? Would that effect it? I installed it like the other one, and it looks correct.

It acts like the thermostat doesn't want to open initially until a higher temp then normal, I don't understand. Should I buy another one and try it? Any other ideas?

This truck has to get me around for 16 days a month whike I'm away from home and I cant afford to have it down again.
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Old 01-31-2012
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Not a mechanic but just thinking out loud.

Is the T-Stat the same temp as the old one ?
No on the stat install, it can go in one way on the ones I have replaced.

Does it heat up quicker than before ?

Did you flush out the system, really well, like twice; with the condition of the coolant, as you stated, there could be a lot of junk still in there.

luck
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Old 01-31-2012
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The thermostat is a standard 195 degree tstat. It warms up fairly quickly, but not alarmingly fast if that makes any sense. I flushed the system very well with the first radiator change, and now its been flushed several times since then, while I was doing all the work. Like I said the coolant seems to flow very well now, aside from the fact that the thermostat seems retarded. Initially I thought it may be the sender but I replaced it, and it seems to have a normal pattern. Or maybe there is another sending unit in there effecting it...?
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Old 01-31-2012
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Quote:
Originally Posted by brianjwilson View Post
The thermostat is a standard 195 degree tstat.
Try a thermometer after the engine has warmed up.
Maybe the gauge, if it has never had a reading as high as when you heated it up, then maybe the mechanism inside of it is just reading higher, a test thermometer will tell for sure.
Not sure where to get one but it needs to be a 250 degree or maybe 300.

Once you determine the real engine temp, when the engine is at normal running temp, then you can set your mind gauge to compensate.

luck.
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Old 02-09-2012
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Any updates Brian?
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