I have a 1990 F150 with a 5.8L 351cid V8 engine. Forgive me, but I am not much of a mechanic, but my temperature gauge climbs to about 1 o'clock and the drops back down about 9 o'clock. Sometimes it will do that several times as I drive. I do not drive the pickup often but still makes me nervous. Is this normal? If not what could be the cause? Also maybe it is all related but if I drive for a while and turn off the engine and then try to restart it while it is still hot, it has problem restarting. Once it wouldn't start again until cooled down. The temperature gauge has never spiked or stayed up high and it has never overheated. Any help or suggestions appreciated!

 

Sounds like a bad connection to the temperature sender on the block. I would start by pulling the wire off of it and cleaning it a little, I'll go find oyu a picture of where it is at...

If it still is jumpy after that, you may need to clean the connection on the back of the cluster (not as likely to have problems since it's not exposed to the elements), or replace the sender. Just to be on the safe side, make sure you're topped of on coolant, as well.

 

The coolant is topped off, I have checked that. I will try and located the temp sender when I get home tonight. Thanks for the picture! I will let you know what I come up with, hopefully tomorrow!

 

If you're standing on the driver side and reach OVER the oil fill cap, you'll basically have your hand on it.

 

If the needle stays in the NORMAL range, then it's normal. If you think the gauge might be wrong, buy something like this:

<-Clickit

 

I appreciate the help guys. I am still trying to find time to get out there and get some work done on it. Another thing occurred to was that cooling fan does not work. Would that be a result of fuse or relay or something bigger?

 

It's a mechanical fan - not electrical. Read this caption: