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Can I have two bad thermostats in a row

Nekkedbob
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Nekkedbob

Nekkedbob

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I have worked on vehicles off and on since the late 60s, gas  and diesel , air cooled and water cooled and haven't had this happen before. I did a coolant flush as it was due and changed the thermostat because it was running about 5 degrees hotter the last year. The first new thermostat that I installed was listed as 190 degree and it did not open until 207 and not close until 183. I filled the radiator through the thermostat hole as i normally do and topped off in the cap , let it run through open 2 cycles. All good . Took it out for a drive of 20 miles with short but steep hills and flats. The first thermostat was very consistently opening at 207 to 208 and closing 182 to 183. Any motor that I have worked on before never varied more than about 3 degrees after maybe 4 open and close cycles on flat road with it being 75 degrees out. I installed a second one that was a 190 by a different parts house and it is doing the same thing but opens at 197 to 198 and closes at any where from 177 to 182. The second one was driven about 135 miles with no change. I did install the old thermostat and all is well but it is a 190 that was installed 4 years ago and after I brought it out of winter storage this year it has been about 5 degrees over normal but very consistent. I have changed more thermostats then I want to remember and cannot remember a bad one out of the box more or less two in a row. The first one was from advance auto and the second one was a napa premium. Is this the new standard or am I the luckiest person in the world this week. My next move will be to go to cummins and just bite the bullet and pay the price unless someone can come up with a better way to go.

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Guest 04Mach1

Guest 04Mach1

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Possible that you may have gotten bad thermostats. I usually check thermostat function with a metal coffee can half full of water heated with a propane torch and monitor the water temperature with an infrared temp gun. 

 

Likely cause of running a little hot could be the outside of the radiator plugged with oil and dirt from the factory located CCV on the front of the engine. I would remove the radiator and clean it with degreaser and low pressure water then reinstall. That may fix your hot issue.

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Tractorman

Tractorman

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7 minutes ago, 04Mach1 said:

Likely cause of running a little hot could be the outside of the radiator plugged with oil and dirt from the factory located CCV on the front of the engine.

 

This is definitely worth looking into.  It took me two years of driving my truck to figure this out because the symptoms manifest slowly over a long period of time.  The blockage that you see on my radiator in the photo covers the front of the radiator between the charge air intercooler and the radiator where it is very difficult to see.  I was always inspecting the radiator on the engine side because that is where I thought the blockage would be.

 

After I cleaned that radiator I was amazed at how much quieter the engine fan became because the air flow became laminar again.  And, of course, the overheating problem went away.

 

- John

6-22-2016 Truck Radiator Blockage (1).JPG

6-22-2016 Truck Radiator Blockage (5).JPG

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Nekkedbob

Nekkedbob

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I all ready cleaned the radiator and installed MPM CCV breather that dumps at the back of the block and the radiator is still clean. Mine looked worse then that when I pulled it. When it was dirty the only time that I noticed a problem was pulling my trailer up hellish grade on highway 88 from NV. into CA.Just a FYI I replaced the radiator 4 years ago when I installed the thermostat and MPM CCV and had to reclean it in the spring because of a failed pvc joint.

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dripley

dripley

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42 minutes ago, Mopar1973Man said:

I've been running NAPA thermostats and never found a bad one yet. :shrug:

I thought I had some bad ones but they worked for you. On top of that my temp is spot  on for 6 months since I messed with the map sensor harness the first time. Maybe longer, I woul have to look that thread up for the time frame.

Edited by dripley
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Nekkedbob

Nekkedbob

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The one from napa was the one that looks like MPM 190 but was listed as premium unit. So far I have asked for Stant and Gates both  and the just list as house brands, no manufacturer. I had a interesting thing today . I crested a fairly steep hill at 189 and about half mile down the other side the temp hit 207 then dropped to 172 before it closed again and was at 198 at the bottom.

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Guest 04Mach1

Guest 04Mach1

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38 minutes ago, Nekkedbob said:

The one from napa was the one that looks like MPM 190 but was listed as premium unit. So far I have asked for Stant and Gates both  and the just list as house brands, no manufacturer. I had a interesting thing today . I crested a fairly steep hill at 189 and about half mile down the other side the temp hit 207 then dropped to 172 before it closed again and was at 198 at the bottom.

Is it possible that there is still air in the cooling system that is being difficult to burp out? I've had a couple of 6BT engines in F750 trucks give me grief like this and it took me putting the cooling system under -30 inhg vacuum to get rid of the air. I filled the cooling system under vacuum to keep air out. After the air was purged from the cooling system the coolant temp would stay steady to almost the thermostat setting no matter how hard it was driven 

I use the Snap-on equivalent to this to fill almost any cooing system I work on now so I don't entrap any air that will cause overheating.

 

https://www.tooldiscounter.com/ItemDisplay.cfm?lookup=MITMV4533&source=froogle&kw=MITMV4533&gclid=Cj0KCQjwn4ncBRCaARIsAFD5-gVxXgxIR4xIMiVNoYha5IVHhSvwmDulNTs1iuZ0UmePMzaoQi4CRjAaAqPhEALw_wcB

Edited by 04Mach1
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Mopar1973Man

Mopar1973Man

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11 hours ago, 04Mach1 said:

Is it possible that there is still air in the cooling system that is being difficult to burp out?

 

Simple solution. When I do my coolant flush on my trucks I leave the thermostats out during the flushing. Then after the system is drained out. Then I close the drain cock and then proceed to fill the block back up with coolant mixture till it just about to run out the thermostat hole. Now install the thermostat and finish filling the cooling system. Now there is nothing left to burp out of the system because its full now. 

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AH64ID

AH64ID

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On 8/25/2018 at 8:26 PM, Nekkedbob said:

The first thermostat was very consistently opening at 207 to 208 and closing 182 to 183. 

 

That appears correct for a Cummins 190° thermostat. 

 

Aftermarket ones should do the same, but I hear too many horror stories about non-OEM thermostats so I stick with Cummins. 

 

Anyhow.. the 190° thermostat crack at 190°±3° and aren't full open until 207°. Max allowable temp 225°. So it seems like everything is operating normally. The fully closed temperature will depend on several things such as radiator temp, engine load, etc. I'll see it dip to the low 180's in the winter if I'm not towing, but normally it won't go much below 187°. 

 

So... I think you're good on the thermostat, but I am surprised you're able to hit 207° without a load. I've never seen my thermostat go full open without towing a decent load. The hottest I've ever gotten without a trailer was 204°, and that was on a 113° day doing 75 up a 6% grade in Az. It's very rare for me to even break 200° without a trailer. I cruise with or without a trailer at 193-195°. So I would double check the radiator for cleanliness or any other blockage.. which could be a/c condenser or intercooler blockage as well. 

Edited by AH64ID
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