Another temp control issue?

[1993]

ok, to start off. My temp gauge seems to work quite accurately.
when it reads 200, the hottest part of the block that I can find(Using a laser thermometer) is at 206, just above the exhaust manifold.

I just flushed the coolant.
lots of tap water(high volume garden hose) with the thermostat out and even the engine running for a short time.
then two fill ups with distilled water and running the engine a few miles at full temp for a few miles.
After final drain, I filled up by adding approximately 3.5 gallons of Rotella ELC(orange). that's as much water volume as I could drain with bottom hose off. I'm guessing it all gets to mix together when the thermostat opens?

I also replaced the thermostat and the thermostatic switch.

temp stays pretty much perfectly at 200

the problem?
if the temp goes a hair above 200, the fan kicks on and does not turn off.
I turned the engine off and then back on when the temp was back at 160.
The fan came back on with the engine and stayed on as the temp slowly crept up to 200.

BEFORE the flush, the thermostat replacement, and thermostatic switch replacement, the fan would either kick on at 160 or not at all.
When the fan did kick on, the temp would hover around 190 and the fan would not turn off.

 

[911joeblow]

Did you open the heater valve during any of this process? If not you might have a lot of air in the heater circuit that is burping into the system and causing steam pockets.

Is your coolant level dropping at all?

Try placing jumper cables from the battery to the block and the chassis and see if all of this changes. If it does you have some ground issues.

Good luck!

 

[1993]

Did you open the heater valve during any of this process? If not you might have a lot of air in the heater circuit that is burping into the system and causing steam pockets.

Is your coolant level dropping at all?

Try placing jumper cables from the battery to the block and the chassis and see if all of this changes. If it does you have some ground issues.

Good luck!

Yes coolant dropped a little, i filled it back to the cold fill line once the engine cooled off.
Going to drive around a bit later and see if anything changes.
all grounding cables I could locate have been cleaned and greased with dielectric grease.
I also installed a massive ground kit upgrade. much heavier gauge than any people are selling online. every connection has a crimped on copper ring connector with dielectric grease and heat shrink tubing.

 

[911joeblow]

So the fact it dropped tells me a couple things might be going on. One as mentioned you may have or had large amounts of unfilled areas of the cooling system that are burping to the overflow tank. Air in the system will cause all manner of weirdness as is can impede the flow of coolant and create localized areas of super-heated steam. This can show up as strange fan engagements, rapid temperature fluctuations, sudden loss of coolant, sudden purging of coolant from the overflow etc... So again turn on your heater full open and drive the truck to see if you have purged it all.

The other more dire possibility is a head gasket, head crack, or block crack. Lets leave those for now though so you can do more testing. Good luck!

 

[JoeJrTheBarber]

Easy way to purge air from a coolant system is to "ice pack" the system. When going for final fill add a bunch of ice with the motor running. As the ice cubes melt they obviously turn to water and will find the / fill the smallest of air pockets. Have done this trick on many vehicles both gasoline and diesel and have had great results.

 

[1993]

is it really that much trouble to purge air out of the system?
My heater valve is always on because the linkage at the valve pops off(dont care to deal with it). when I turn the heater fan on I get plenty of hot air.

I drove the truck around a bit more.
coolant level looks good.
fan kicked on before 200 and stayed on.
temp stayed unflinchingly just under 200.

Any other thoughts?

 

[Thecaptain]

A couple of quick thoughts- have you put a new radiator cap on? When I swapped my thermostat it was bad out of the box. Beyond that, unfortunately, I think your going to need to crack open the tm and follow the troubleshooting procedures for your fan. Checking voltages and functionality of the individual components. From what you’re describing your system isn’t functioning as it’s designed to: thermostat should open about 195, fan should kick on at about 205 and cut off about 190 - but your temps should drop back down a little lower than that. If the fan is running full time - should operate about 180.

Cap

 

[1993]

A couple of quick thoughts- have you put a new radiator cap on? When I swapped my thermostat it was bad out of the box. Beyond that, unfortunately, I think your going to need to crack open the tm and follow the troubleshooting procedures for your fan. Checking voltages and functionality of the individual components. From what you’re describing your system isn’t functioning as it’s designed to: thermostat should open about 195, fan should kick on at about 205 and cut off about 190 - but your temps should drop back down a little lower than that. If the fan is running full time - should operate about 160.

Cap

wow! my temp definitely does not drop down anywhere near 160 and the fan is running.
What part of the engine should I be testing the temp with my laser thermometer?
radiator cap is new.

 

[1993]

A couple of quick thoughts- have you put a new radiator cap on? When I swapped my thermostat it was bad out of the box. Beyond that, unfortunately, I think your going to need to crack open the tm and follow the troubleshooting procedures for your fan. Checking voltages and functionality of the individual components. From what you’re describing your system isn’t functioning as it’s designed to: thermostat should open about 195, fan should kick on at about 205 and cut off about 190 - but your temps should drop back down a little lower than that. If the fan is running full time - should operate about 160.

Cap

how did you know the thermostat was bad out of the box?
I bought a duralast from my local autozone.
supposed to be the same, it fit but does look a bit different. they told me it opens at 190.

 

[Thecaptain]

Thermostat wasn’t opening. You can feel the lower hose and return hose - if the engine is hot and those hoses are not - thermostat isn’t opening/coolant isn’t circulating. I can usually watch my gauge and when my temp hits about 190, I see it drop and hold for a while because the thermostat opened. But if you run at 200 for extended periods, your thermostat probably is probably opening. I think most people recommended testing at the crossover.

I used something like this to troubleshoot (I’m on my phone, so this may not be the exact one I used). https://hummerhuren.files.wordpress.com/2013/01/hmmwv_test-diagnostics.pdf#page9

Cap

 

[Action]

how did you know the thermostat was bad out of the box?
I bought a duralast from my local autozone.
supposed to be the same, it fit but does look a bit different. they told me it opens at 190.

Put it in water on the stove. Use a thermometer to see what temp the water is when the thermostat opens.

 

[Thecaptain]

Put it in water on the stove. Use a thermometer to see what temp the water is when the thermostat opens.

This is the most accurate way to determine without having to consider other variables like air pockets.

 

[1993]

Thermostat wasn’t opening. You can feel the lower hose and return hose - if the engine is hot and those hoses are not - thermostat isn’t opening/coolant isn’t circulating. I can usually watch my gauge and when my temp hits about 190, I see it drop and hold for a while because the thermostat opened. But if you run at 200 for extended periods, your thermostat probably is probably opening. I think most people recommended testing at the crossover.

I used something like this to troubleshoot (I’m on my phone, so this may not be the exact one I used). https://hummerhuren.files.wordpress.com/2013/01/hmmwv_test-diagnostics.pdf#page9

Cap

Yup that's the one I've been looking through.

So I just went out to the shop and started it up.
was still warm from the short drive a little earlier.
started up at 160. same temp at the crossover and the gauge on dash.
fan running right from the start.
Earlier, when I started the truck cold, the fan did not engage until just under 200.

with laser thermometer in hand, the temp on the crossover near the thermostatic switch rose perfectly along with the gauge inside.
right up to 200.
I kept checking the temps just past the thermostat, as well as the upper radiator hose, and the radiator.
At about when the crossover got to 198, the temps past the thermostat began to rise.
the highest temps at the crossover briefly kept rising to just over 200 and then dropped down to 196 and stay there.
the temp on the dash gauge also got to 200 and then dropped a hair below.
fan keeps running.

could the new thermostatic switch be bad?
is the thermostat waiting too long before opening?
​and..
What could be happening with the fan?!

 

[ken]

If the thermostat you used is a 195 then It should not drop below that. Even if the fan runs all the time the thermostat will close and hold the temp. I think you have a caddy valve problem and or a module problem. They are the round valve and little black box mounted on the drivers side right by the washer bottle.
As for purging the air, not it's not that much trouble. The 3/8 inch hose mounted by the thermostat that also goes to the overflow tank will purge the air out. With the cap off and the engine cool, start the engine. Along with the heater valve open, and you mentioned that it is. The water pump will force the air out and drop the coolant level in the over flow tank. Since you had this happen already and you have drivin it, I'm pretty certain you have gotten the air out. These two parts, the valve and the module are common failure parts. I too have replaced mine. I also replaced my thermostat with a 180. And my thermo switch with a 195. So now my fan comes on at 195 and off at 184. No more over heating!

 

[1993]

If the thermostat you used is a 195 then It should not drop below that. Even if the fan runs all the time the thermostat will close and hold the temp. I think you have a caddy valve problem and or a module problem. They are the round valve and little black box mounted on the drivers side right by the washer bottle.
As for purging the air, not it's not that much trouble. The 3/8 inch hose mounted by the thermostat that also goes to the overflow tank will purge the air out. With the cap off and the engine cool, start the engine. Along with the heater valve open, and you mentioned that it is. The water pump will force the air out and drop the coolant level in the over flow tank. Since you had this happen already and you have drivin it, I'm pretty certain you have gotten the air out. These two parts, the valve and the module are common failure parts. I too have replaced mine. I also replaced my thermostat with a 180. And my thermo switch with a 195. So now my fan comes on at 195 and off at 184. No more over heating!

What part numbers do you have for the thermostat and thermostatic switch that you installed?
I didn't realize that there is more than one option for the switch. Thanks!

 

[Thecaptain]

Have you tried unplugging the tdm? You could check your Thermostatic switch - boil some water and see if the circuit opens. It’s not unusual to have bad parts out of the box.

 

[1993]

Have you tried unplugging the tdm? You could check your Thermostatic switch - boil some water and see if the circuit opens. It’s not unusual to have bad parts out of the box.

Well it definitely opens because the fan turns on. but it stays on until the truck has cooled to way below 160. if I restart the truck at 160, the fan will still be on.
when the truck is cold, I can turn the fan on by disconnecting the TDM.
Is there a part number that supersedes the original TDM? I have found different part numbers out there for the M998

What is the difference between the thermostatic flow control module and the TDM?
Which one should I replace first?

 

[ken]

What part numbers do you have for the thermostat and thermostatic switch that you installed?
I didn't realize that there is more than one option for the switch. Thanks!

I used a Milodon 16406 thermostat from Summit Racing. For the switch I used Switch number 8037024 from Fanclutch.com You have to cut the wires off of the old switch and use connectors or soder them onto the new switch. Now mine never gets hotter than 195 and no more worries about blown head gaskets and or cracked heads.

 

[cwajciec]

Sounds like the Time delay module is not kicking the fan off at the right time. It could be a bad tdm or a bad temperature sensor that tells the tdm to engage. The tm has procedures to test the system.

 

[Action]

Well it definitely opens because the fan turns on.........,,,?[/FONT]

What does one of those have to do with the other?