Lately after driving at highway speeds for a good length of time the temp gauge will climb up to the M or A of NORMAL. IIRC it used to stay between the O and R. I flushed all the coolant out a while back and replaced with 50/50 and since then it has been doing this. It's still in range but makes me uncomfortable since different than before. No coolant loss. Also if I get off interstate and travel on slower roads with stop and go traffic or just idle the gauge will drop lower between R and M. Any ideas? I've used an infrared thermometer all over the engine and all temps seem ok.

 

Mine was going as high as M just for a bit during hill climbs, but drops back to R, its been hot has hell here the past week. How about thermostats? As long as it isn't going up to L I would think it would be ok, Like I said mine will do it sometimes to but it always drops back down.

 

Pulled codes yet? O2 sensor(s), thermostat, fan clutch, fan shroud, vacuum leaks, timing....what am I missing to check?

 

I hear the fan shroud could be a huge factor, I saw somebody post about that hear not to long ago.

 

its possible the fanclutch is failing or has failed, i would start there if it appears to be the stock unit. and a fan shroud is a must.

 

Fan clutch is original and that's what I'm thinking. Is there a simple way to test it?

 

With the engine off, spin the fan, if it makes more than one revolution, it is bad.

Jim

 

no codes. fan shroud in place. fan clutch seems fine. i'm going to replace the thermostat and go from there.

 

how many miles on the motor? the fan clutch is easier to replace and frankly makes more sense. a Tstat either works or or doesnt.

 

Not necessarily tstats can be partially open/closed causing inefficient flow and higher than normal temps.

 

The 96 computer system is different from my 94 so don't know if this applies to you. Mine was running a little too hot for my preferences. The tailpipe looked new. I replaced my oxygen sensor (Bosch) with Motorcraft even though no codes for it were showing. Temperature went down to 195-205 on Texas August highway. Tailpipe became black.

 

Might be a possibility. I believe my O2 sensor is original. Did they come with Bosch originally or was that from a prior replacement? How can I tell what's 195-205 on a gauge that reads C to H with a large NORMAL in between?

Right now I'm wondering if this all may be electrical. I went to pull codes yesterday and then noticed the radio wasn't on. The code reader said link error. I jiggled the code reader connector and the radio came back on. I'm not sure if these two things are related or not but this is the first time I observed this. I was able to get a good connection and it showed no codes. I went out today not to pull codes but just to crank it up and pull it in so I could work on it and I still don't have a radio. I can get the display to flash and hear a little blip in the right door speaker if I move the ignition from acc to off but it won't stay on. I'm not sure what's going on or where to start with this thing.

 

I had the same problem with my 96 a while back. The gauge was getting hotter while driving on the highway than while idling. Part of the problem was I was low on coolant. Sounds dumb I know but I didn't check that first because I thought I was okay. However, the other main part of the problem was that I had a small blockage in my radiator, which also caused a small leak. After replacing the radiator, I have had no issues.

I would check around the radiator really well and make sure there are no damaged fins/rust spots coming from anywhere. If you do have rust spots, that means the radiator is starting to corrode and that could mean the coolant flow is highly restricted in the radiator itself.

 

"Might be a possibility. I believe my O2 sensor is original. Did they come with Bosch originally or was that from a prior replacement? How can I tell what's 195-205 on a gauge that reads C to H with a large NORMAL in between? "

My Bronco had 152K when purchased so I suspect it did not come with Bosch. Good mechanical oil pressure and temperature gauges mounted under the ash tray give much more info than the instrument panel ones.