Need cooling system help

[kb426]

On my 32 with the 5.0 Ford. I changed thermostats about 700 miles ago when I changed engines. I went from a 160 to a 180. It worked fine. At 500 miles, I got mad at the engine and removed it. I reinstalled the 5.0 that I had in the truck for the first 1500 miles. I didn't touch the thermostat or the housing. I make a 100 mile trip and it works properly. I drive around town a couple of days and it works fine. Tuesday evening I get in it to go to a town 27 miles away and it never makes it above 150 degrees. I eat supper and return. Same thing. Today I removed the thermostat. It was closed. I played with the new one and the old one with my heat gun and the infared temp. gun. They both appeared to work properly. I installed the new one and it never made it to 150 before it appeared to be open. I've used the infared gun and checked all over the engine and am reasonably sure the engine temp gauge is accurate. It's not blowing coolant out like a head gasket is leaking. What could have possibly happened with the truck sitting for an hour and being fine and then not? I'm not finding anything wrong. I took the old thermostat into the house and heated a can of water. As far as I can check, it didn't open until 180 which leads me to believe that something in the engine is causing this. Has anybody seen this before? Should I find a priest or an exorcist and turn them loose?  :?

[phat46]

Maybe the gauge is bad? I'd try a different one.

[kb426]

I'm double checking the engine temp with a handheld infared gun and it agrees with the engine temp gauge.

[ragdol]

If the temp guage is working, then the thermostat couldn't be opening, right? Is the thermostat installed properly? Right gasket, installed properly? Is it possible that the themostat is "floating" in the housing, effectively not doing it's job? Somehow it appears that the coolant is bypassing the thermostat. Larry

[wayne petty]

just curious....    is there a bypass hose between the intake or thermostat housing and the water pump?  

any heater core?   any heater hoses that dump into the radiator???

with your temp gun....   are you measuring the thermostat housing... the intake coolant crossover???  any visible part of the heads... the top hose.. the lower hose... the radiator tank?

i take it that it is a small block ford...

is it the proper rotation pump??? some fords have reverse rotation pumps and pump plates...   there have been instances of reverse rotation timing covers...

more info is needed....   perhaps even casting numbers off the water pumps....


high gauntlet welding gloves...  2 plastic cups of water..  one for hot water, one for cooler water, a microwave oven..  shaking the microwave to make water is stirred before opening so it does not explode as it is totally possible to heat still water way above the boiling point of water... which erupts when you move it...   NOT GOOD....

using long nose pliers to dip the thermostat into the boiling hot water... it should open.. then into the cooler water.. is should close...

i may have misread the post... i am tired and my glasses are dirty... but using a hot air gun to test thermostats is a bad idea... there is a rubber section inside the bulb... overheating that will damage the stat..

at low coolant levels or when the engine is truly overheated to where there is steam keeping the coolant back from the stat will usually not heat the wax inside the stat bulb enough to force the piston out ..

[kb426]

Wayne, there is a bypass hose in the factory location, heater core is hooked to the 2 factory locations, not back to the radiator. I used the temp gun all over the place. The readings on the manifold and thermostat housing correspond with the gauge reading. This is a reverse rotation pump setup.  Don't forget that this setup worked fine for 600 miles since installing the first 180 thermostat before it decided to make me crazy. The thermostat that I removed I played with the the water on the stove as you suggested. It worked fine. No sign of early opening or not closing when cooled.

[wayne petty]

the only other place that i might think might cause something like this is when a factory intake manifold has the heater core elbow swapped out... some of them have an extension that sticks through a divider in the intake...

just a thought...

[kb426]

This engine had the tubular water lines that run to the back of the engine. I removed all that when I put it in the 32. It has regular hoses on it now. I guess this weekend I'll go get another thermostat and change it. I don't have much hope for different results at this point. I've never been lucky enough to have stuff automatically fix itself.

[enjenjo]

Are you sure they gave you the right stat? I seem to remember one that will fit in a Ford, but is not deep enough to cut off the water flow.

[kb426]

This one fits in the small recess in the housing. All of them I have are the same diameter. The 160 that was removed when I changed engines that was working properly is the same diameter.

[C9]

400-M's - which is a Cleveland - use a thermostat that has a round block-off device on the bottom.

When the engine is cold, the thermostat proper is closed and the block-off is open so that coolant is recirculated in the engine only which makes for a faster warmup.

When the engine is warm, the thermostat is open, the block-off closes the bypass and all coolant goes through the radiator.


A few years back I stuck a Chevy thermostat - 180* vs the stock Ford (only temp available at the time) 197* thermostat - in my 400-M.

The water bypass remained open because the Chevy thrermostat had no provisions for a block-off.

Results were, the engine ran hot, but not overly hot.
About 3/4 of the way up the stock gauge which used to run right in the middle with the original Ford 197* thermostat.

It was cured by tapping the bypass hole in the bottom of the thermostat well and installing an Allen flush plug.
This allowed the Chevy thermostat to operate correctly and the engine ran cool like it should, but not overly cool like yours is doing.

Not sure if this helps, but thought I'd toss it in.


When you use your heat gun on other engines/cars does it agree with the temperature gauge?

And are you shooting the engine at the same place the sending unit is?

I'm wondering about the gauge and heat gun or not, perhaps a swap or temporary install of a cheap temp gauge would tell you a lot.

[kb426]

I got bored and changed the thermostat again just in case I had got 2 bad ones in a row. Same results. I'm down to the logic that something appears to be causing the thermostat to open way early. All the bypass and heater hoses are in their original locations. C9, when the engine hits about 120 degrees you can feel the upper radiator hose and tell that water is circulating through it. I can run around town and let the temp rise to 180 and then go out on the highway and in a half a mile, it will be back around 150 degrees. I'm puzzled as to how this worked properly and then it didn't with no changes except for starting the engine and driving down the road.

[Mikej]

The way I see it you need more horsepower to develope more heat thus raising the water temp.  or your bragging because your car runs so cool. Just kidding....... I wish mine ran 150. Is this a performance stat by chance? Mine has 4 bypass holes and won't warm up in cold weather. Also the pill end goes toward the water. Good luck.

[kb426]

Mikej, everyday thermostat. 2 Stants, 2 Motorrads from an independent jobber. Yes, the pill is towards the water in the manifold. The temp has been in the 70's when this is happening. I doubt if it's a 100 out, I'll be noticing this problem.  

[C9]

The way I see it you need more horsepower to develope more heat thus raising the water temp.  or your bragging because your car runs so cool. Just kidding....... I wish mine ran 150. Is this a performance stat by chance? Mine has 4 bypass holes and won't warm up in cold weather. Also the pill end goes toward the water. Good luck.

One 1/8" hole is enough.

I tried two 1/8" holes in the roadster's 462" Buick engine thermostat.
In a four mile trip to the donut shop where the gang meets on Saturday mornings, the temp gauge hit 180* F about a half mile away.
40 mph road for most of the way.
Didn't help that the ambient temp was in the 24-28* range at the time.

A week later, virtually the same ambient temp, but this time with a one 1/8" hole thermostat.
The gauge - an accurate S-W mechanical that reflects 1* changes and you can see the thermostat operating had the engine at 180* F about a mile and a half from the house.

It was nice to get some heat from the heater.


Is your heater putting out air about the same temp as it did/should?

I'm still leaning toward a bad temp gauge.

Buy a good - or even a cheap one - mechanical gauge and give that a try.


Got a candy thermometer?

They make a good device for testing actual radiator coolant temp.

You can probably duplicate your problem by leaving the radiator cap on the first notch so you don't blow coolant in your face when you remove the cap on a hot engine/radiator.

Run the car until the temp backs off to the low temp at highway speeds, pull over, remove cap - be careful, helps to have a towel over the cap for safety while you remove it - and stick the candy thermometer in the coolant.

It would help if a passenger stays in the car to call out what the dashboard temp gauge reads.


More than a few guys would like to have your overly cool problem, but I think it's something as simple as a bad sender on an electric gauge or similar.


Another thought - and this is the reason for the 1/8" holes in my thermostat - is that you have an airlock and the radiator/engine isn't full of coolant like it should be.

Part of this depends on where the sender is located, but airlocks I've had will usually not allow much coolant in and when the engine does get hot enough to open the stat, when the stat does open, the sender is out of the coolant and in an air pocket.

Senders need to be submerged in coolant for them to work properly and when they're not, they will have the gauge reading low.

Drill a 1/8" hole in the thermostat flange and try that.
(There's usually plenty of room for the 1/8" hole without impinging on the thermostat mechanism or ending up with it sealed off by the gasket.)

With the engine and radiator full of coolant, the problem will probably go away.

(It doesn't take long for the air to bleed through the 1/8" thermostat hole and you'll be assured of a complete coolant fill.)