I'm tracking some weird engine temp issues, and I asked this before, but I think I was too specific, so now very generally:

Is there anything I'm not thinking of that can cause an engine to "underheat", or more accurately, cool too well? I'm dealing with just a really annoying range right now, between 140, and 230*, entirely based on how fast I'm moving, and the ambient air temperature.... in summer.

How do I tighten up that range?

Why is my engine doing this?

I have the proper T-stat for my Cleveland (400), and it's a 192*. And yes, it's installed the right way up. And I don't run a shroud at the moment, so I'm not nearly as worried about the top end, but how do I get the bottom up?

AleX

 

Do you know anything about the fan/fan clutch? (Inspect how the fan turns with the engine cold and hot assuming that you have a thermal fan clutch)

Assuming the t-stat is properly functioning, that is the only thing that I can think of.

With a shroud your temp probably wouldn't be getting near 230, but I see that you are trying to fix the cool running problem.

 

Well I know of the existence of aaa fan clutch, but I don't what it is, or how it works, or what trucks have one, because I don't believe I have one.....

My fan is bolted right through to my water pump, which is attached by belt and pulley to the crank pulley. That's it...... so I am 99% positive I don't have a fan clutch, but I'd be interested to get a summary of one regardless.

And yes, I know the shroud would help my high temps. I only hit 230* on a hot hot summer day when I'm not moving at all, but right, getting the temp up is the real mystery.

 

Sure sounds like a thermostat open all of the time,but you say it's new and installed correct . Sensor pellet towards the engine,not the radiator ?

 

Well that's what I thought too, so I replaced it, but no dice. And I replaced it with a "Robert Shaw" from Flowkooler, thinking the old one must have been for a non clevo, only to pop off the water neck and find the eXACT same unit I was holding in my hand!

Replaced it anyway, and yes, copper sensor down, empty cone up. Standard water pump, non high flow.

 

Should I have a fan clutch?

 

a properly functioning fan clutch would stop drawing so much air through the radiator once the temp starts falling below 190* ish.

but without a fan shroud, i doubt your fan is "pulling" much air through the radiator anyway.

It REALLY sounds like your t-stat is sticking open. It is possible to get a bad one out of the box, but usually not two in a row.... i'm kinda stumped.

 

Right I know, it's just expanding metal, the whole thing based on AVERAGES of expansion rates, and friction, for specific metal alloys, and if you get an outlyer on either side, that will of course be a "bad one", but right, these are two of the best automotive thermostats on the market, purchased at two separate times, likely from two different suppliers.

I've been running a very weak antifreeze mixture to save on that cost recently, since I've been doing alot of engine work (draining and refilling). Could that have anything to do with this?

 

a stronger solution would likely have better heat transfer, which might help your high-end temp problem, but i doubt it would likely affect your "running cold' problem.

Have you been able to verify these temps with an infared gun? or at least a different gauge?

Is it possible that a hose is routed incorrectly effectively bypassing the thermostat?

just throwin' out idears ....

 

Is it possible whatever gauge your useing is inacurate?

 

a fan clutch is the physical connection between the waterpump shaft and the fan blades.

How a Car Engine Cooling Fan Clutch Works - 2CarPros

some people will remove the fan clutch and replace it with a spacer for a solid connection that will pull air at 100% capacity all the time. This is good for cooling, but very bad for horsepower.

your best balance of horsepower consumed and cooling effort provided is a stock fan with a properly working thermostatic fan clutch. when working properly, the fan will freewheel when the engine temps are below about 190* (it still spins but not at the same rate), and will engage above that point (with a noticable "roar" of air movement when engaged)

I'd suggest this setup, but it will not likely help much with your running cool issue .. seems like there is something else going on ... just gotta get our finger on it.

 

First of all, noooot a problem at all, idears are exactly what I'm looking for.

But right, exaaaactly, the overheating has never been a concern. It was a little annoying in the summer, but it never even got so bad I had to pull over, and I always watched it, AND, like we've said, I have any number of tricks still up my sleeve, to correct it, but I have never heard ANYTHING to indicate to me that antifreeze cools LESS than just plain old water on the bottom end.

To border and 73, no I have not gotten any "second opinion" on this from any other instrument, but my gauge is new, and everything on a normal warm up tells me that it's working fine. And what I know of my truck also tells me that it's not the gauge. When I get real low, like 150, 145, stuff like that (highway, any weather below 70) the engine chugs a little more, and my gas mileage PLUMMETS, and there's nothing I can do about it! And when it get's up high high the engine sloooows down juuust a little, and, my electric choke carb adjusts itself veeeery much inline with the gauge, and where my head thinks the engine should be. Point being, I'll test it with something else sometime soon, but that just doesn't seem to be the problem. It holds very nicely right at 190* too, on a hot day moving about 30-50.

And I don't think I have anything routed wrong.... one fat hose from the top of the block with the thermo in it, to the top of the rad, one hose from the bottom of the rad to the water pump. Heater hoses where they should be (although I guessss it's possible they're reversed, that make a difference?).

The more you talk about it though, the one thing that DOES sound likely, is that fan clutch. Did trucks as old as ours have them originally??? I've never known my truck was supposed to if so..... I have a big 5 blade metal one, pretty steep angles, and fat blades. It's one of the last things in the truck I've never replaced! Is it wrong???

And if so, where can I pick up a cheap clutched fan to test?

 

The t-stat is going to control the engine temp no matter what the radiator or outside temp is going on. Otherwise, if it is 0 degrees outside the engine would never heat up.

If the engine is cooling too well, then the t-stat is either opening too soon or being bypassed.

Josh

 

Well then I don't know what to say. That was my logic, what's the fan matter, if the temp is so low that the thermo is closed. But here I am.

Is it at allll possible that my engine just isn't generating enough heat? Like, could the thermo be closed this whole time? Maybe since I don't have a fan clutch?

 

Shouldn't matter... the t-stat will stay closed, effectively eliminating the radiator and fan from the equation until it senses the proper heat and begins to open.

Once it opens it allows the coolant to flow into the radiator allowing it to cool where is then begins the trip back into the engine... the t-stat senses cooler coolant and closes allowing it to heat back up. It's an endless cycle and happening spontaneously.

With a 195 t-stat, I could run the MarkVIII fan on low or high and still maintain the same 195-200 temperature. Of course, what that really does is make the t-stat work that much harder instead of working in conjuction with an automatic fan/ clutch fan.

You are in fact intalling the CORRECT 351M/400 t-stat and not some off the shelf unit right? They require a different style than 95% of engines made.

Josh