Bad temp gauge or gonna blow up?

[WarMonger]

My truck (from what the gauge says) has been running warmer lately. Plus, the gauge is moving in temp a lot. You know right before your thermostat opens, you see the gauge climb a little then it drops when the thermostat opens? Well mine seems to climb a little higher than normal, then it drops a lot, then it climbs again, drops a lot. I have a 3 core alum radiator and she normally runs really cool. Yes, I have fluid in it. no leaks that I know of. So Bad, gauge, thermostat or gonna blow up?

[B. W.]

My guess is thermostat. when a gauge is bad it usually goes high or low, it doesn't fluctuate. The tstat is sticking & then opening at a higher temp. Even if this is NOT the problem it's cheap to try & eliminates one variable.

[weq92f]

It's gonna blow up.

-klb

LOL

[WarMonger]

WTF weq92f No, I will try the thermostat and let you guys know the outcome. Start with the cheap parts first.

[demian5]

How about using a temp gun to check temperatures of the engine and compare to the gauge. Where is your temp sender? If its reading the t stat that much, my assumption is its in the intake manifold by the t stat housing. I would move it to the head as the factory intended the temp to be monitored.

The middle of the gauge could be 200 degrees and is OK. As long as it's not pinging or having detonation issues, the higher the combustion tempos, the more fuel is burnt efficiently.

Your fan does look like it sits inside the shroud a bit too much.

My 70 with a stock 350 barely comes off the first tick after the cold mark. I have never thought about it running cold, I just figured its a poor sender or old gauge in my case. I have a 180 with a 4-row radiator, shroud and fan clutch. Heater gets plenty hot.

[davepl]

I'll pile on about the fan - if you have spacer, toss it I think. You want it half in, half out of the shroud usually.

The middle of the gauge is about 200 when I checked once. That's about where a 195F thermostat should open.

[WarMonger]

Update. while changing the thermostat, one of my friends stopped by. Whom, i believe is smarter than me. He said grab the fan and see if it spins. Engine is cold. Fan spins both directions with no resistance. No it is not electric. does this mean the fan clutch is bad?
Note... put in new thermostat, it did not fix anything.

[WarMonger]

Originally Posted by davepl

I'll pile on about the fan - if you have spacer, toss it I think. You want it half in, half out of the shroud usually.

The middle of the gauge is about 200 when I checked once. That's about where a 195F thermostat should open.

I have had the fan in this place since we built the truck. For the last year it has been running ice cold. So I believe it is another problem. But I'm open to anything.

[LockDoc]

Originally Posted by WarMonger

Update. while changing the thermostat, one of my friends stopped by. Whom, i believe is smarter than me. He said grab the fan and see if it spins. Engine is cold. Fan spins both directions with no resistance. No it is not electric. does this mean the fan clutch is bad?
Note... put in new thermostat, it did not fix anything.

Fan should turn but it should have quite a bit of resistance. I would say that your fan clutch is possibly bad. You didn't say where your sender is located.

If the picture you posted is all the hotter it gets by the gauge, the radiator has coolant in it and it's not boiling over, I wouldn't worry about it....

LockDoc

[demian5]

Originally Posted by WarMonger

Update. while changing the thermostat, one of my friends stopped by. Whom, i believe is smarter than me. He said grab the fan and see if it spins. Engine is cold. Fan spins both directions with no resistance. No it is not electric. does this mean the fan clutch is bad?
Note... put in new thermostat, it did not fix anything.

Fan clutch if OK. Locks up when hot. Should spin free when cold.

Get a temperature gun and confirm the engine is actually getting hot.

What degree t stat did you pull out and put back in?

[WarMonger]

Just remove these to get the fan clutch out? Not the 4 bolts on the water pump?

[WarMonger]

Originally Posted by WarMonger

Just remove these to get the fan clutch out? Not the 4 bolts on the water pump?

fan spins free when hot or cold

[WarMonger]

Originally Posted by LockDoc

Fan should turn but it should have quite a bit of resistance. I would say that your fan clutch is possibly bad. You didn't say where your sender is located.

If the picture you posted is all the hotter it gets by the gauge, the radiator has coolant in it and it's not boiling over, I wouldn't worry about it....

LockDoc

Sender is located on top of manifold. It is pretty new.

[WarMonger]

Originally Posted by demian5

Fan clutch if OK. Locks up when hot. Should spin free when cold.

Get a temperature gun and confirm the engine is actually getting hot.

What degree t stat did you pull out and put back in?

195 old and new. my temp gun is at home. fan free spins when engine is hot or cold.

[demian5]

You gotta take the bolts off the water pump pulley to get the fan and fan clutch off, then remove those bolts.

Ok another question: Does it only get hot when sitting and running or when going down the freeway?

[weq92f]

The bad clutch may explain the hotter than normal gauge reading as well as the higher cycling range during thermostat cycles that you observed.

As for the too cool, that could be too cool a thermostat or something else but it sounds like you need a new clutch ( and maybe change the location in the shroud ) and you'll be back to 'normal'


-klb

[LockDoc]

Originally Posted by WarMonger

Sender is located on top of manifold. It is pretty new.

It will work there but that location is not ideal, as there will be more fluctuation in the gauge as one would expect, because of the thermostat opening and closing. I realize the problem you are facing with the later style heads too....

LockDoc

[WarMonger]

Originally Posted by LockDoc

It will work there but that location is not ideal, as there will be more fluctuation in the gauge as one would expect, because of the thermostat opening and closing. I realize the problem you are facing with the later style heads too....

LockDoc

So should I get a different shroud or fan?

[demian5]

Does it only get hot when sitting and running or when going down the freeway?

[LockDoc]

Originally Posted by WarMonger

So should I get a different shroud or fan?

I would get a different fan clutch, even if you could find one that will work at your local pick-n-pull to see what happens.... They interchange between different older vehicles. There may be a small amount of difference in them as far as how fast they kick in, but not enough to worry about. Just make sure the bolt locations match.

LockDoc

[WarMonger]

**Update**
put in new fan clutch. Drove it around for about 20 minutes then let is idle for 15 and this is where the temp stayed. thanks for all your help guys.

[LockDoc]

Originally Posted by WarMonger

**Update**
put in new fan clutch. Drove it around for about 20 minutes then let is idle for 15 and this is where the temp stayed. thanks for all your help guys.

Good deal! Glad you got it sorted out.... And thanks for coming back and posting the fix, too many people don't do that.

LockDoc

[dfwright]

Leon beat me to it, but I was going to say the same thing. Thanks for the closure -- so many threads never get updated with the final results.

[WarMonger]

tomorrow we figure out why my brake lights dont work.

[weq92f]

Nice! ++on the closure thing.

-klb