Temp Gauge Fluctuating - caused by head gasket leak ?

[ratterrier]

Hi folks,

Here's the lowdown...the temp gauge on my 96 Explorer moves up and down a lot. It rises enough to set off the check gauge light at times. Usually keeping the heater switched on prevents it from going that high. The gauge will read near the top, and then fairly quickly drop down to a cold reading. Most times, the gauge will stablilze after a while, but again this is with the heater switched on.

Another problem surfaced some time ago, where one of my head gaskets weeps coolant. It doesn't leak so much that one would notice...the coolant level doesn't noticeably drop. Since I don't have the skills or cash to get this properly repaired at this time, a mechanic put in a can of sealer a while ago (I think it was called BC or BG brand). I believe it is supposed to have fiber in it to plug leaks.

I was wondering if the gauge fluctuation is caused by a build up and release of pressure from the point of leakage in the gasket. It seems to me that it would constantly release some hot coolant, and no build up would happen. It's hard to believe an engine could heat and cool so quickly. So although the gasket is a problem, might there be another reason for the gauge to go awry ? That is, is this a common complaint for Explorers ? Or could the sealant itself cause the gauge/sensor to go bad ?

Thanks for any advice !

Richard

 

[shamaal]

First off, do you have sufficient coolant? If so, you're most likely problem is a sticky thermostat. Yes, the temperature can rise quickly, particularly at a stop. Next likely is cooling system blockage, generally speaking this would be the radiator. Use of a sealant should have no effect on the gauge temp sensor.

From a cooling perspective, leaking heads will cause a loss of coolant but no other effects that will cause your temp gauge to fluctuate. Depending on the location and severity of the leak, it can cause problems that range from poisoning your O2 sensors to filling a cylinder with non-compressible water. If the leak is in the right place, you can drive with leaking headgaskets for years, provided you keep your radiator topped off.
Your first order of business is getting your cooling system up to snuff. Replacing the thermostat is fairly easy - 3 10mm bolts on the V6 OHV.

 

[Mbrooks420]

You should probably quit driving an overheating vehicle unless you want cracked heads. If you have a leaking head gasket it should be fixed. The thermostat is cheap enough it should be replaced just to rule it out. If it fixes it I wouldn't forget about the head gasket.

 

[ratterrier]

Thanks for responding !

Today I installed a new thermostat and gasket (Stant 29959 /195 F), and replaced the amount of coolant I drained out with fresh coolant...didn't do the whole system because my coolant recycling container was already close to full. So I took it for a test drive and was happy for about 2 miles. I had the heater off and the temp gauge was leveling out at the middle. So to make the trip more worthwhile I stopped off to fill it with gas, than headed back home. Shortly after leaving the pumps the gauge maxed out, and I quickly turned on the heater and raised the the heat up. This helped, but for some reason the temp gauge seems a bit worse than before. When I got home the gauge was getting close to maxing out again even with the heat high and running. Usually I just have to turn the heater on, and not really increase the temperature. Getting to work tomorrow may be quite an adventure.

Does anyone have any recommendations on the next step ? Am I looking at a new radiator? Is it likely the sealant has fouled it ? And why would having the heater on help if the radiator was plugged...it's only adding some extra circulation.

Thanks once again..

 

[Mbrooks420]

Have the radiator pressure tested. Then fix the headgasket and you'll be fine. These heads aren't known for durability. Overheat them too much one time and they'll crack. Then it will be more than twice as much as fixing it properly the first time.

 

[shamaal]

See #5 for the standard fan clutch test:
http://www.explorerforum.com/forums/showthread.php?t=162407

If it passes, things don't look good for the radiator. It's a pretty basic system. All this troubleshooting assumes that you are not overheating because of a loss of coolant.

The reason the heater being on drops the temp is that you are removing heat. Think of it as an extra radiator.

As Mbrooks 420 says driving overheated is not good, bad gasket or cracked heads are a common result. Let us know how it turns out.

 

[jasonwimbrow]

similiar problem here at first the temp guage would shot up and drop to normal every so often . so i changed the t-stat the top hose, coolin temp sensor, collant sending unit . thought i flushed the whole system out drove to end of dtreet and went all the way und and didnt come back down any help would be great wife is stuck without a ride. btw 1999 explorer pushrod v6. PLEASE HELP!