Thermostats and their temp rating vs. heaters

[kc5mzd]

I have a feeling that the thermostat is not closing the port to the radiator, either because it isnt fitting properly or there is no gasket allowing water to flow past when it is in the closed position. I would lean in the direction of it not seating without the gasket but don't know without having it taken apart to look at.

The easiest way is to take temp readings after a 15 min warmup. There should be a signifigant diffrence between the head where the tstat housing bolts up and the top of the tstat near the upper raidiator hose.

Its important to go ahead and fix it. Not only will it not allow the heater to work properly but you could run into a lot of problems overheating especially in the summer. If the tstat is not properly closing off the bypass port when it is hot you will overheat when you are under any kind of load - like going up hills or pulling a small trailer.

 

[shootist]

I have a feeling that the thermostat is not closing the port to the radiator, either because it isnt fitting properly or there is no gasket allowing water to flow past when it is in the closed position. I would lean in the direction of it not seating without the gasket but don't know without having it taken apart to look at.

The easiest way is to take temp readings after a 15 min warmup. There should be a signifigant diffrence between the head where the tstat housing bolts up and the top of the tstat near the upper raidiator hose.

Its important to go ahead and fix it. Not only will it not allow the heater to work properly but you could run into a lot of problems overheating especially in the summer. If the tstat is not properly closing off the bypass port when it is hot you will overheat when you are under any kind of load - like going up hills or pulling a small trailer.

I'll check the temps tomorrow- I have a feeeling the gasket is the issue.
Like I said earlier there was none there-but also the tstat was a more"modern"
one also-about half the size of the new one-
any ideas where I could pick up one of the top gaskets?
I dont know why they wouldnt send one with it?

 

[kc5mzd]

is this what the new one looked like?

 

[shootist]

yes that is the one

 

[kc5mzd]

Thats good. You will know more when you get temp readings. I was looking for the ir thermometer I have. It works good but I didn't see one to get a pic of - I am away from home today. I did notice Harbor Freight Tools has one for $15.00. I dont know how well it is made but havn't seen them that cheep...

 

[shootist]

another update

Ok took temp readings after running for about a half hour 40 minutes......

IN radiator: 135
Tstat housing near head/bypass elbow: 157
Head at tstat housing: 167 +/-
Back of head at #6 cylnder: 170 176
Water pump: 155

There is no noticeable flow in the radiator- although I think there may be a very small amount.
I also closed the heater valves on the bypass and the #6 cylinder, to check the temps.
I ran truck with cap open for 20 min before closing.
Obviously the tstat never opened.
Idol was just about a hair above normal (to help heat it up)
When I did shut the truck down a couple times during the temp checks I noticed the temp jumped about 10 degrees in all locations almost instantly but the water pump,radiator, and tstat housing (housing jumped about 5 degrees)
stayed the same. When I restarted each time everything went back to the temps mentioned above.

Now Im even more confused.

 

[kc5mzd]

A 180 deg thermostat should start to open around 165-170 and could account for the head temps. If it is very cold outside 30deg is very cold (I'm from Texas) when the thermostat starts to open it will bring in cold water from the radiator which first enters the water pump making it colder than he rest of the engine. The radiator by the upper radiator hose should be even cooler because the hot water from the engine mixes cold water in the radiator. The radiator near the lower radiator hose should be the coldest point in the entire system. The colder the outside temp the lower the temp should be in the radiator by the lower hose.
It seems to be working close to what I would expect. When the engine is around 160 or more by #6 you should be getting considerable hot air out of the heater. At that point I would start looking for restrictoins in the heater lines. You can also check the temp of the heater hoses. They should be hotest by #6 and cooler as they exit the heater core. No diffrence might sugest a bad fan or heater core. A huge diffrence might sugest not enough water flow.

If you want to get the tstat to open you can try placing a plastic bag or card board infront of the radiator to stop airflow. When you get the water by the lower radiator hose up to around 140 or more you should start to notice considerable flow in the radiator. You should keep an eye in it to prevent overheating when covering the radiator.

Also what did the guage inside read when the engine was 165 -175? you should have an idea whether it is accurate.

 

[Oldfart]

I think some of these M37/M43 engine cooling arrangements were very efficient. I do recall a winter that was particularly cold here in Colorado and I never could get heat out of my system sufficient to run a engine coolant cab heater. I usually placed a sheet of news paper over the radiator allowing the fan to hold it in place. I could drive 5 miles to work and the engine would not overheat (but I could get some heat out of the cab heater.) One time when it was really cold, I placed a paper over the radiator and just let the truck idle for hours. It never did get hot and I surmised that if it was cold enough ambient temperature the block itself was dissipating enough heat to keep things from overheating. ~~~ I often thought I should switch from the civilian cab heater to the stock military gas heater mounted on the fender.

 

[shootist]

Ya, no hot air out of the blower at any temp. just "luke warm"
I figured I would get at least "warmer than out side" air.....
The temp gauge seems consistent with the head temp.
I used to be able to over heat a car with out trying-now Im trying
to over heat a vehicle and cant even get it "hot"!!
I'm going to try blocking off the air flow to radiator an see what happens-
I just find it so hard to believe that I cant get this tstat to open.
With the old tstat (stuck open)I had instant "luke warm" air in about 5 minutes
and flow in all the lines but with no pressure-now with the new tstat
(closed) I get nothing not even any pressure build up.
I'm slowly growing disgruntled.
Do I need the heater? no not at all, but now that I have it installed
I figure-better work and work right!
Originally I thought about putting a flamer on but I was concerned If I ever got hit or hit anything
it would look like a napalm incident

 

[Oldfart]

The reason I did not install a gas fired heater was the fact that the majority of my driving was off road in the Colorado Rockies. I hauled a 5 gallon can in the outside can mount and then usually a couple of 5 gallon cans lashed down in the bed. If I got in to snow or any condition that mean lots of time running without going anywhere I would have to add fuel before I got home. A gas heater just cuts the fuel mileage and it was bad enough as it was.

I did manage to get some heat out of the engine coolant heater when I went to a 195 degree thermostat and replaced the radiator cap with a higher pressure unit. I think I wound up with 13 PSI after trying 7 PSI. Note that I said "some" heat. Without the top on you could not tell there was a heater. With the top cover in place, I could get some heat to the defrosters, but there never was anything like "toasty" warm. My next step was to replace the civilian heater core with a different unit that I got out of the back of a passenger van. It was larger and should have provided more BTU's that what might have been available from a smaller core (came out of an old Dodge Pickup.) I never got that done, but I did also visit Jack Tomlin in Utah and I bought a military hot water under dash heater that was somewhat larger than the old Dodge heater. I never got around to installing that either. When I get some time, I plan on finishing the rebuilt engine install and replacing the civilian heater with the military unit.

P.S.
Just occurred to me that there is a tin tube that fits in the engine and helps distribute the engine coolant through the block. If that is rusted out, you might not be getting proper circulation.

 

[kc5mzd]

I would start troubleshooting the heater and hoses now that you can get the head to 160.
One thing I would try is disconnecting both heater hoses from the engine and taking a garden hose on low hold it to one of the heater hoses and see if the water flows easily through the heater system.
If you get good flow with a garden hose the next thing would be to take the fittings of the head and the bypass. Go to Home Depot or a similiar store nearby and get fittings that will fit the threads on the head and bypass that will allow you to connect the hoses directly without any valves or adapters.
When you get to that point after everything you have done I am confident that when the head gets to 160+ you will get heat. If the head gets over 170 you should get very hot air.

 

[shootist]

Im gonna try the old Indian garden hose trick later today.
I'll post after the experiment

 

[shootist]

Ok sorry for delay in posting what I did-
I got the paint and body work bug again
Drained and flushed heater unit and hoses- no restrictions there.
Drained and flushed cooling jacket around block- no issues there.
Drained and flushed radiator -no issues there

Ran it a bit after an afternoon of flushing filling and draining,
I even blocked off the airflow through radiator
when it was around 60 degrees out and STILL
cant get the **** tstat to open, cant even get the engine "hot"
although I did notice a slight increase in the temp from the heater
(only have to wear 2 insulated jackets now when cold out instead of 3)
I got the head around the # 6 cylinder to around 185-195 degrees this time
but I think that side of the head runs hotter maybe? or its reflective heat from the manifolds.
Radiator at top inside still only gets to around 134
tstat housing maintained around 160 that time
and the head around the tstat on manifold side was around 170 and 155 or so on the opposite side. I did notice a minor amount of flow through the top of the radiator after an hour at a moderate idol.
funny thing is like I said head on the manifold side runs around 10 to 15 degrees hotter maybe more (which Im guessing is normal )then the opposite side and rear runs 15 to 20 degrees hotter than front on same sides.
Maybe Im concerned over nothing. but the heat still sucks

 

[Oldfart]

OK, 185-195 is hot enough to get heat that you can feel out of a cab heater. By #6 is where the hot water comes from to the heater core. If the flow is unrestricted through the cab heater core, then there is not enough flow to supply your required heat or the heater core is too small to supply adequate exchange over the time the hot water is in the core.

What I am trying to say is the hot water is not flowing fast enough to supply the heat or the core is too small and only a small amount of heat is being transfered. I would install the cab heater return line to the metal elbow in the water pump return line from the bottom of the radiator. If installed there and out of the nipple next to #6 in the head That will be the maximum flow possible. If you are currently plumbed that way then your heater core is too small. When I was younger I used to scrounge junkyards for convertibles because they had a larger heater core than a regular sedan. They would look the same as the sedan, but they put out more heat.

 

[shootist]

Interesting concept I had thought about connecting it there. but something didn't seem right. Maybe Im missing something

curious--if the bottom line in radiator is the feed to the cooling jacket
and the top hose is the return from that jacket to the radiator, that means that the anti freeze entering the heater core from the #6 area is returned to the radiator after passing through the heater core via the bypass elbow.

so if I move the heater core return from the bypass elbow to the "feed"(bottom hose) from the radiator wouldn't that create a neutral type flow basically connecting it to 2 feeds
for lack of a better term?

 

[Oldfart]

No.

The water pump bottom hose elbow is taking the coolest water out of the radiator and the water pump is pumping it into the front of the block. This cool water is pushed down both sides of the cylinders gaining heat along the way until it gets to the back of the block. The block has small holes that allow the coolant from the block to enter the head around each cylinder. That water then travels back forward through the head to the thermostat housing where it is delayed by the thermostat on its return to the radiator. The reason the front of the head is cooler than the rear is the fact that the coolant has spent less time collecting heat in the front. As the water progresses farther back in the block, it has more time to collect heat before it enters the head for the trip back to the radiator.

If you are plumbed to anywhere on the head and anywhere on the return line (top) hose you have nearly the same head (pressure) on both sides of the heater core. You need your cab heater hoses to be attached to opposite sides of the water pump impeller. You can attach the heater hoses to the thermostat housing bypass instead of the nipple next to #6 Cylinders, but the water will be hotter back by #6. If you are attached to the #6 nipple and the thermostat housing, the only pressure difference would be caused by the extra drag of the water having to move through the block. Any real flow would likely be from the thermostat housing through the heater core and back in to the head. Either takes the hot water from the thermostat housing or #6 area of the head and returns it to the intake side of the water pump.

I did not mention the tin piping that fits in the block and helps to circulate the water through the block in an effort to keep the temperatures more even along the block. If this gets rusted out (it often does and usually does not get replaced on a rebuild) the temperatures along the block can vary greatly. I have seen some rebuilders that actually pull this "diffuser" and leave it out as it does not come in most rebuild kits.

 

[shootist]

update

Ok
I ran the truck today to check the temp of the air at the distribution box in the cab.
After running it for around 8-10 min at a moderate idol.
I turned the fan on and the air leaving the box was at around 150-160 degrees.
I guess this is much hotter than it feels on your hand!
I didn't check the head temp, took a quick look at the gauge it seems to be pretty close in past tests it was at around 140 or so (I'm guessing) only because it starts at 60 and then the next temp is 180.

I think I may try to connect at the lower radiator metal pipe, there is a fitting on it to connect. If I cant get the tstat to open.
I do have a pretty good flow at the heater core, since I flushed everything out and changed the fluid.

next on the minor issue list (not that this issue has been solved yet for sure)......which is before the major issue list.....
the clicking sound at the speedo............. does it ever end
Just when I thought I was finally done!!!!

 

[Thunder in NWOR]

Couple comments:
When I was a kid, my dad had a 1949 Dodge PU with the 230.
The heater in that truck never got above "warm" air out of it.
He frequently in the winter wired a piece of cardboard over part of the radiator to get the water temp to run higher.

When I bought my Dodge Command Car, I had temp problems. Pulled the tstat and it was broken - open. Replaced the tstat (NAPA part) and the thing overheated on a hot day. Pulled the tstat and dropped it in a pan of hot water - would not open (bad out of the box). Got another new tstat (midwest military) put it in pan of water - opened at correct temp (used mommas cooking thermometer - unhappy momma when she caught me) - result no trouble since.
Tip - many 230 (and 218 and 251) engines (with long time since rebuild) have a trashed water distribution tube that will cause water flow problems. Oh, and its easy to put the late market tstats in upside down.

now - lube the speedo cable before it hangs up and breaks! (you are never done!!!!)

 

[shootist]

now - lube the speedo cable before it hangs up and breaks! (you are never done!!!!)

maybe I should start a new thread speedo's cables and their issues

for now I guess I'll ask here:

I replaced the non functioning speedo with another I had
I found when I removed the original Pvt Pyle had placed electrical
tape around the cable end itself and "squeezed over" the actual speedo nipple.
WHen I got it out I found I could operate it by hand but not in the truck......go figure.
I put the spare in and found that the cable "clicked" in to that ones nipple.
When I drove it I heard a heck of a "clicking" that sounded like it was coming from the back of the speedo or the cable itself and the needle was bouncing all over the place-
Im gonna pull that one tomorrow to make sure the cable is still locked in
now for the question: Ive read here you can "oil" the speedo itself- how??
and how does one "lube" the cable?

TO answer above: Im pretty sure the tstat is in correctly key word being pretty sure... its an original type I think there's a pic of it here a couple pages back

 

[Oldfart]

It sounds like the drive nipple in the speedo head is slipping on the cable or the cable is dry and catching on the cable housing. You can lube the cable with graphite, leave lubricants out of the speedo head with the possible exception of odometer gears. A kinked or pinched speedo cable housing could cause the problem. Noise is heard at the speedo head because that is where the erratic cable movement is being delivered.