The Stovebolt Site Forums The Shop Area Engine Shop 58 235 cooling system

I’ve recently done a tear down and rebuild of a Chevrolet 235 for my 58 fleetside.

Couple of simple questions.

What temperature thermostat should I use? It had a 180° thermostat, but temperature gauge seems to read in the low range. Doesn’t hit the painted ‘normal’ range. A friend said to use a 195° instead. Said it actually reduces wear on the engine.

I have the ‘deluxe’ heater. Which heater hose goes to the thermostat housing?

Thanks.

John D,

While I don't have an answer to your question on which "thermostat" to use, here is a link to help with your heater hose routing and connections question.

Am sure that others will chime in here to discuss and try to help on your thermostat question soon.

Dan

John D I must be using 180 in my 51 6400 because it stays on about 185 degrees summer and winter. This is with the original big radiator,heater works OK ,cab isn't real tight. If you have enough radiator to run 195 that would be even better if you don't overheat like in a traffic stall. Pressure cap is in that picture,along with how good your heater core is.

A 160 degree thermostat was fairly common on older vehicles, yours probably has one as well. It allowed the engine to warm up quicker and to keep from overheating while keeping the operating pressure lower. Most modern vehicles run a 195 thermostat to work with better with fuel injection as the fuel mixture is regulated by a computer and requires a consistent temperature.

As long as your truck is not running hot or having issues warming up I would recommend you stay with the thermostat that is currently installed.

Thanks for your answers folks.
Now I have to check which nipples are on the thermostat and water pump housings.

I put my 4 thermostats in a pot on the stove to see how they are operating. I think the old bellows type has higher flow rate. Two 180° modern type are fairly consistent opening and closing. One 160° likes to open early and close late. Not going to use that one.

I live in a small southern Ontario town. Our summers are moderate. No traffic to cause problems and I don’t drive the truck when it’s blazing hot and no A/C. Probably need heat on more spring and fall days. Rad seems to be in OK shape. So 180° thermostat is probably a good spec for me.

Thanks for your follow-up.

I like your multi-measuring device testing set-up - LOL!

Once you get your stuff back together and the engine up to normal temp, maybe use that digital temp reader to scan your engine to see what it reads VS your dash gauge. Doesn't hurt to compare and see if the issue may just be a slightly inaccurate dash guage???

Interested to see what results you get.

Dan

W/r/t "It allowed the engine to warm up quicker"
The thermostat temperature has nothing to do with it. The engine will reach 160 at the same time with any closed thermostat.

As said, a 195 thermostat gives better cabin heat, keeps the oil cleaner by boiling off the water vapor, and will allow leaner cruise mixture for mileage (if your system and heater core will stand the pressure).
The down-side? a 195 thermostat makes the engine more knock-sensitive.

You didn't say what type of cap you are using. You should not use a pressure cap with a bellows type thermostat. The 195 should not be used in a no or low pressure system.
The gauges on these trucks are just an indicator.

George

Hi Dan.
I did use my laser thermometer to check when I did my first check run after my rebuild. It ran for about 1/2 hour outside on a day about the freezing mark with heater not connected. Thermostat housing was about 185° but my dash gauge was just off cold. My gauge has no markings. Too much salt on the road for a proper test run. In the past I have seen my gauge go to hot area when it was low on coolant so the temp sender seems to work.

I wanted to know about plumbing for the deluxe heater as I had removed it to correct the temp control cables. Prior to this I had no leeks.

So today after reconnecting the heater hoses and thermostat housing, I refilled the rad.
I thought all was well until I found coolant leaking on the floor. Not from all the hoses. Seems to be leaking out of the heater. Arrrgh.

I had flushed the core before reconnecting the heat cable. Seems that I did something wrong and maybe buggered the ranco valve.

So tomorrow I’ll have to pull the heater out again. Such a painful job. Hope it’s a simple fix, though it probably isn’t.

John.

Hi George.
Thanks for your advice.

I have a 7 lbs pressure cap. I put a non bellows 180°thermostat back in.

Yes, I know the gauge is an indicator only. No graduations for reference. I just thought maybe it should read somewhere in the center when at normal operating temperature instead or reading at the low end.

After re reading my manual, I guess anywhere but at the hot end of the scale is OK, provided I know that the engine and cooling systems are functioning properly. F

Sometimes the only warning I have of overheating is that sour "penny in your mouth" taste from antifreeze boil-over.

What method did you use to flush the heater core? Anything with more than about 5 psi of pressure (shop air or garden hose) will split the seams and heater cores always seem to be the weak link...

Mike B

1958 deuxe heater has a rubber hose inside heater control assembly between heater core and control valve......may be source of leak

Update on heater leak.

I’m trying to figure out where the leak is without pulling the heater out of the cab.

When I flushed the core I didn’t have it under pressure. Just flowing through. Don’t think I could have over pressurized it.

There is no sign of a leak under the heater on my rubber floor mat. I pushed in some paper towel in a hole on the bottom right of the heater box. Comes out clean and dry. I removed the little floor heat grill, shoved my iPhone inside the heater box and it looks clean and dry.

I rigged up two 3/4” hoses and connected to heater inlet and outlet. Connected to my air hose with about 5 psi pressure. No sound of a leaking air.

I changed my hoses and filled the core with clean water and let it sit for an hour. Probably lots of trapped air. No loss of water at lower hose, which are higher than engine height. No air pressure. No different than when I first filled radiator. Engine never ran.

I I did find coolant under the foam flooring under pad. So between the steel floor and floor padding. After drying out the coolant, I left a clean dry paper towel under the floor pad directly under the heater. So far it’s staying dry.

When it was leaking coolant it was dripping pretty consistently, not a drip or two. I’m starting to think that I didn’t get the gear clamps tight enough and coolant was leaking past the hose and just dripping down the inside of the steel floor pan.

Any opinions on the use of gear clamps vs spring clamps?

Thinking about refilling with coolant and checking for leeks without battery box so I have better visibility.

Worm gear style clamps work just fine but make sure they're tight and sized correctly. Don't use one that's too big and try to crank it down to a small diameter hose that it isn't designed for. It won't keep its circular shape.

Be sure the hose nipples are round- - - -once they get squeezed oval by overtightening a clamp it's very difficult to get a good seal. When I worked part time at a radiator shop we had a special pair of internal expanding pliers to round out flattened hose nipples.
Jerry

John D Wont your thermostats on the bottom of the pan open from burner heat ?? I thought you lowered them in on a wire once the water was up to temperature.