Thermostats and their temp rating vs. heaters

[shootist]

Ok
what really is the difference between a 160 and 180 degree
thermostat-besides the obvious temp rating/opening/closing

If running a water heater-Can you run a 160 tstat?

will it be "warm enough"?

is the reason the tm calls for a 180 tstat with the heater so it generates more heat?

Has anyone run a 160 with a heater? how did it work? good enough, not well etc-

how about a 180 vs 160 tstat in the summer?

Reason I'm asking is: I'm pretty sure I have a 160 in my truck only because it never really gets "hot" no matter how long it runs-gauge it self barely moves (bad maybe) it has descent flow in radiator but nothing like I think it should be- it's more of a very slow steady flow not very turbulent like I expected, but the heat at the distribution box is more like "slightly warm air" no good for chilly driving-and oddly enough- although all lines (feeds and returns) get hot -there is no pressure........ so my guess is probably a bad tstat
not sure what to replace it with- I haven't really found much info in the tms or here on the site regarding the 160/180 tstats and heaters vs. summer/winter etc

 

[YTS Deuce]

160 degrees is really too cool for an engine to operate ideally. High horse gas motors can do it, but no advantage whatsoever in a Diesel. In fact, a diesel will be much happier at 195 degrees than it will be at 160.

I would recommend putting a 180 thermostat in it. If it gets cold where you live, I'd try to get a 195 degree thermostat.

 

[Bill W]

I ran a 160° stat ( napa THM-55 ) in my 37 for years and felt it was fine, other have stated that running a 180° stat (napaTHM-155 ) gets the engine hot enough to burn off moisture & impurities in the oil and makes for a better burn/combustion in the cylinders....I still ran a 160°. NAPA still sells the stats ( I just checked their website )

 

[Oldfart]

I am old enough to remember changing T-stats between summer and winter as a part of the regular service on some older cars. The usual switch was from 180 to 195 for winter and back to 180 for summer. Worn out engines got a 160 in the summer to keep the oil from thining too much. I had an engine so worn I ran 50 weight and modified a T-stat to open even eariler than 160. I managed to squeeze an extra 3 years out that engine.

That being said, I don't think the lack of personell heat is due totally to the T-stat temp range. It sounds like there may be a restriction in the heater line. I did run across an M37 once that someone had added a cab heater supplied by engine coolant. It was plumbed to two different locations on the same side of the water pump. Things would heat up, but there was very little flow through the heater core as the pressure on both sides of the core was essentially neutral. I have seen cases where increasing the heater hose size made a difference in the amount of heat out of the heater.

 

[shootist]

Well it seems there is plenty of flow through the heater unit lines.
I think the tstat may be stuck open, because no matter how long the truck runs
I'm not getting any pressure in any of the coolant lines.
I've drained re-drained and bleed out the air.
I guess the next step would be to decide on a 180 and a 160
I think I may pick up both and see which one seems to work better with the unit.
Although with summer approaching ..............
not much need for heat. but I would like to figure out what the issue is.
I suppose NAPA wont have the water pump and by pass gaskets?

 

[shootist]

I don't think the lack of personell heat is due totally to the T-stat temp range. It sounds like there may be a restriction in the heater line. I did run across an M37 once that someone had added a cab heater supplied by engine coolant. It was plumbed to two different locations on the same side of the water pump. Things would heat up, but there was very little flow through the heater core as the pressure on both sides of the core was essentially neutral. I have seen cases where increasing the heater hose size made a difference in the amount of heat out of the heater.

Thanks for the tip here is what I did: I connected it per TM to bypass elbow at water pump, and to connection next to the #6 cylinder, opened the new valves all the way only because it doesn't tell ya how much to open 'em, there's flow but no pressure.

 

[rosco]

The noticeable heat at you heater comes from the top of your heat range. You can't trust the readings on your gauges!. Use something like and inferred thermometer to see what you have. I Always run here, the hottest thermostat I can get - especially on a diesel. They get tired and usually the temp drops with age, both on the engine and the thermostat. The hottest thermostat will not make your engine overheat. A faulty cooling system or head gasket leak does that.

 

[Oldfart]

Going into more detail about my experience with my M37 and its after market engine coolant cab heater, I will say that I went from 160 to 180 and then to 195 T-stats trying to get enough heat out of the cab heater. After that I discovered two things. One was that the cab heater was plumbed from the back of the head to a nipple on the T-stat housing. Second was that in the install of the cab heater, one of the water line nipples to the heater core was bent up to clear the fender inside the side cowl resulting in a restriction to flow. When I plumbed things correctly I got more heat and when I opened up the core nipple the heat got even better.

I did encounter an overheating problem with the 195 degree T-stat. While operating in the Denver, CO area at about a mile in elevation, things were fine. However wandering around some gorgeous mountain spots above timber line, my M37 would boil over. I eventually replaced the radiator cap with a more modern version and stepped up the pressure range. I saved the old cap because it was original, but it was definitely weak.

You mention pressure in the heater coolant line and turbulence in the radiator. There is not much pressure produced by the water pump. A city based garden hose is usually around 45 psi or less in an effort to keep sink faucets from dripping. Most home well systems are even less because most home/farm domestic wells need to keep delivery below available volume. I don't recall the pressure specs off a new Dodge 230 water pump, but I don't think it would be much above 10 lbs. At idle 5 pounds would not surprise me. ~~ Lack of turbulence in the radiator might mean your T-stat was stuck shut or that your water pump was worn out (both conditions should make your engine over heat.) The M37 radiator is fairly large for the engine size and it is possible the T-stat is stuck open (or missing) causing the engine coolant to not stay in the engine long enough to reach any driving range temperature. The radiator is large enough it can dissipate the engine heat passed into the coolant even though it is not retained in the radiator very long. (Most vehicle systems will over heat without a T-stat as the fluid does not spend enough time in the radiator to get very cool.)

Why don't check the T-stat by making a cold start and observing the flow with the rad cap off and feeling the return radiator hose at the top. You should be able to feel an increase in temperature in the hose when the T-stat opens and also see an increase in flow in the radiator top tank.

 

[WillWagner]

There could be no stat in it. That would cause low heater temps and lots of turbulence in the radiator.

 

[shootist]

I ordered a 180 this morning and a new radiator cap (original is still on truck)
I think that its probably one of two things mentioned above-
either the tstat is stuck open or stuck partially open
or just plain missing.
reason being is there is no pressure build up at all in lines or radiator,
with a constant flow of fluid.
The lines get warm, funny thing is the radiator is cool to the touch
after running for a couple hours.......
So Im guessing (hoping really) that its just a tstat issue
should be in by Friday.
I appreciate all the input!

 

[kc5mzd]

Make sure the hose connected to the waterpump is near the lower radiator hose. If it is anywhere near the tstat or the upper radiator hose you won't get enough flow.

I always use 160 - 170 tstats here in Texas. The engines will run at about the same temp as a 180 -195 will up north.

The rating is the temp the tstat is fully open. If you use a 195 in 20deg weather the engine will run at about 170 because the water coming in is very cold when the tstat first starts to open. Also the tm considers 90deg extreme heat. I run in "extreme heat" most of the time. When I use a 170deg tstat the engine will run about 170-185.

It sounds like you may be missing the tstat in your case. I also agree that a inexpensive infra red thermometer is a "Must Have". Your hoses may not be connected to the ideal location if it is not on the side of the waterpump that has the lower radiator hose connected to it.

 

[shootist]

Make sure the hose connected to the water pump is near the lower radiator hose. If it is anywhere near the tstat or the upper radiator hose you won't get enough flow.
Your hoses may not be connected to the ideal location if it is not on the side of the water pump that has the lower radiator hose connected to it.

I connected it to the by pass elbow at the water pump like the TM said.
are you saying to connect it where there is a plug in the lower radiator hose?
I thought that "plug" was a bleeder of sorts?
I have flow at the heater I mean it doesn't "shoot out" when I open the air bleeder on it but it does flow out?
I'll take a pic of the connections.
let me know

 

[shootist]

ok- the first pic is the connection at the bypass elbow on top of water pump before the tstat housing-
second is at the #6 cylinder near back of head.

 

[kc5mzd]

Thanks for the pics. From what I can tell it looks like a very good spot for hoses. It looks like the one on the bypass is right on top of the water pump. It should about the best flow there that you will get anywhere on the engine. The one on the back of the engine looks good also. The top of the head is usually the hottest part of the engine so you should have a good supply of hot water.
The next thing will be to look to see if there is a thermostat. I would guess there probably isn't one. If you are in RI you should probably use a 180 or hotter thermostat.
Be very careful taking the thermostat housing bolts off. If they seem to tight don't force them or they will break. If they are old and corroded inside then you will need to use LOTS of heat on the bolts. Antifreeze can crystallize over time and the heat will melt the corrosion and loosen the bolts enough to take them out without breaking them.

 

[shootist]

update

OK here it is:
old tstat was stuck open it was a 190-that explains the flow in radiator almost immediately and the lack of pressure or heat build up-
now new issue
Installed a new cap and a 180 tstat today...................
Ran the truck at a moderate idol for an hour..........
tstat did not open........
checked the temp in radiator (due to no pressure again)
and it only made it to 140-145. (the truck gauge reads about that also)
Drove it down the road (first time on road by the way! thats a story for another time though) about 5 mi total - still tstat didn't open and radiator at about 140-5
it is about 35 here today but that shouldn't really matter
by the way I could not find in the tm which way the tstat installs so I put it in "spring" down "gate" up.
any ideas or suggestions on this new potential issue

 

[kc5mzd]

The Thermostat has a pellet side I cant remember if it is the side with the spring or not. Be sure the side with the round tube or "pellet" is facing the engine and not the radiator. If you install it backwards it will not open and the engine will overheat. Your engine block should get to about 160 - 170 before any water moves through the radiator. The top of the radiator should start to warm and the bottem of the radiator should stay cold.

It would help if you got one of those infra red Thermometers (about 25.00) at a nearby auto parts store. Then take a few temp readings, on the head by the exhaust manifold (not on the exshaust manifold), at the base of the thermostat housing by the head, at the top of the radiator and at the bottem of the radiator.

Make sure you do the tests with the heater off first. Let the engine run for about 15 min to heat up.

 

[kc5mzd]

I forgot - run it without the cap for the first 15 min to allow the air to bleed out...
Don't drive it without the cap.

 

[kc5mzd]

Also looking back at the pics I noticed the Tstat bypass is looks like it is part of the tstat housing. If the thermostat is below the bypass (on the engine side) then the bypass won't work properly and the heater might be allowing water to go around the thermostat and into the radiator.
If you could take more pics including the thermostat housing without the thermostat off the engine. the top of the water pump when the thermostat housing is removed it would be helpfull. Also I can't seem to find a copy of the tm is there any way you could send me a copy?

 

[kc5mzd]

Found this, make sure that the top thermostat gasket is in good shape and properly installed.

 

[shootist]

funny the tstat doesn't look anything like that one in the tm?
I got it from Vintage pw
and there was no gasket for the "top"? even on the one I took out?
just one for where the tstat housing meets the head.
here are couple pics
it looks as though the "gate" portion of the tstat
is about at the same elevation as the bypass connection to the tstat housing
I drew a terrible sketch of the tstat instead of removing it again.
I will if I have to but would rather not LOL. I dont think I could put it in the opposite way (with valve down toward engine and "spring" up
which tm do you need?
the one for the heater install or?