Hi all,

Hopefully someone here could give me some advice or point me in the right direction. I've got a 1985 F150 with a 302 FI.

I've noticed lately that my temperatur gauge sometimes fluctuates.

Generally, its reads between the "O" and "R" on the temperature gauge, but sometimes for what seems to be no apparent reason goes up to a little over the half way point of the gauge but eventually goes back to where it normally sits.

I've checked the radiator coolent level, looks good, has new thermostat, dosent show symptoms of head gasket or anything, in all honesty. Is it just the gauge fluctuating? what are some things I can check to see?

Also I just noticed the other day, it appears that the oil gauge is also up and down sometimes as well. But again, the Truck is running great and I cant seem to figure this out.

any help will be greatly apprciated.

thanks,
Josh

 

I'm bumping this because I'm having the same problems myself, 94 f150 302 EFI.
Replaced the thermostat a month or so ago and the engine temp has been fluctuating ever since then. I burped the coolant system yesterday after replacing a hose that busted, ran with the radiator cap off to for a few minutes to make sure I had coolant flow, and the problem is a lot better now but still exists.
I guess the next thing to look at is either my water pump or my hoses but I'm pretty sure my hoses are all good.

 

well both rigs should have a 195* stat in them. seeing the gauge fluctuate isnt a bad thing, what your seeing is the tstat being closed so the motor gets to temp and then the stat opens bringing the temps down. if you are at all worried get a new thermostat housing that has a spot for a mechanical temp gauge. this way you know what the true temp is.

you may also check your fan, if it spins to freely when its cold it may need to be replaced. Do not run a solid/flex fan

 

The thermostat opening/closing is what I thought was happening, I was just worried that it wasn't normal since I replaced the Tstat after my previous one stuck.
I replaced my Tstat housing when I replaced my Tstat, is the spot for a mechanical gauge on the top by a large allen head screw? If so then I'll pick up a mechanical gauge.

 

More likely to have air pockets still in the system. I've personally never seen sudden temp fluctuations once the T-stat opens. Once it opens, it pretty well stays open. Other than that, I'd suspect the temp sensor or the gauge itself is acting up.

 

You say that the oil gauge also sometimes goes up and down as well. If this happens in synch with the temperature gauge going up, then it could be a bad ground in the dash or a faulty dash voltage regulator.

I concur that low coolant level will cause these temperature fluctuations, but you apparently have eliminated that.