The Stovebolt Site Forums The Shop Area Engine Shop Overheating again.....

I replaced a bunch of parts on my truck but it keeps overheating. I'm getting frustrated. Ok so the truck started to overheat some time ago and I decided it was in my best interest to replace rather then diagnose why based on the truck's age. (56 chevy 3200) Besides it all looked old under the hood anyways. So i bought a new waterpump w/ gasket, new t-stat w/gasket and new upper and lower rad. hoses. I had a vintage add-on heater but I decided it's hot outside so I'd plug off the heater hose ports. The rad. looks great for it's age so I left it alone. I put everything on and had no problems. I fired it up and everything was fine. However, I drove it down the street and it started getting hot within two- three minutes and then pegs on the "h".
I felt both hoses when I stopped and there isn't a huge difference in temp between the hoses. Any ideas? I think I'm missing something here. What is the right temp rating for these 235 engines? I'm pretty sure mine is a 180f.

If both hoses are the same temp and the engine is overheating, then it sounds like you don't have circulation. There's a number of questions to answer, however.

1) How do you know that it's overheating?
2) Are you losing fluid?
3) Do you know what the temp was when it overheated?
4) Were either of the hoses collapsed when you checked them?
5) Is the fan turning when the engine is running?

You possibly have a large air pocket with the heater blocked off. See if your radiator is low after it cools.
Scott

Ok went back out and tried to figure it out again, used what they call an anti-spill funnel for filling rad. I got it from snap-on and it's like a small bucket the fits on top of the rad. with an adapter so the water/coolant going in will be higher than the engine (air pocket problems) thought this would work for sure but it idled for about 5-7 mins then it blew coolant everywhere out of the bucket! This really [censored] me off, I use the bucket on Hondas and this never happens. I refilled it with water and ran it again without that bucket deal. Checked the hose temp. with a raytech infrared thermometer. Upper hose was around 178 at the top hose right around the upper outlet, lower was around 156 before going into the waterpump. I thought that the rating on t-stat's was at max. (like 180 was when the coolant reachs 180 it's fully open). I'm confused, I replaced the brass sender in the cylinder head last year and it worked fine. I'm ready to make the wife angry and start boiling t-stat's and sender's on the stove in a pot.

fyi, not losing any unless I turn the truck off, it then overflows a little. my truck never had a overflow bottle, it just has a tube down the side of the rad. to the ground.

The gauge is original and it seems to work fine, it gradually increases until it's in the middle.

When I removed the old t-stat it was a 180 but it was stuck open.

Hoses(new) have springs in them and haven't collapsed, the fan is original and the belt is new, the fan turns fine. It seems to do better at idle then on the road....

I hate to say this, but it sounds like you might have a blown head gasket. If you have access to a compression gauge, I'd check the compression on all the cylinders. If they all check normal, pull the oil dipstick and see if there's an water on top of the oil (look for a white foamy substance or clear liquid.)

I had a Willys that would overheat in spite of an OK looking radiator. On closer inspection - the top tank of the radiator showed signs of buckling outward.

Turns out the rad was plugged up fierce. Recore fixed the problem.

-Boyo

Run the engine with a vacuum guage hooked to the manifold. see what reading/readings you get...

Is your sender an original 1956 Delco? The aftermarket units for 1956 have incorrect impedance and show hot when the coolant reaches about 185 to 190 degrees. If you measure an aftermarket unit with an ohmmeter, it will read about 500 ohms at room temperature. An original 1956 Delco unit measure about 650 to 700 ohms at room temperature. I found a used Delco sender from a 1956 truck in a wrecking yard and my gauge works correctly now.

Get an under dash gauge until you can find the correct sender. You will find that you are not overheating.

I hate when the coolant spews out after refilling the cooling system. You had an air/steam pocket. Drill a small hole about a 1/16-inch in the thermostat to let the air/steam escape. Otherwise, if air is trapped in system after refilling coolant, the escaping air/steam pocket will spew coolant all over the place when the thermostat opens. I learned this after it happened to me. The original style thermostat had a butterfly valve that was not air tight, so spewing coolant is not a problem until a modern airtight thermostat is installed

What is the flushing history of your block and head? When you open the tiny drain cock on the lower back driver side of the block does nice clean coolant flow out? The hole in the thermostat is a good idea. I put in 3/16 holes in mine. I recently lost a head on a gmc 228. When I pulled it, I foung that most of the coolant nozzles at the head gasket surface were plugged off with rust and scale. Mineral deposits come with the tap water you add to the system. Use of distilled water can help with that. Modern coolants have corrosion inhibitors. If you are running less coolant with tap water, the job may not be getting done.
I would drain all your coolant into a clean container and examine it. Then I would pull the thermostat, bypass the heater with a crimped hose looped back to the connections at the water pump, install a 1/4" full port ball valve with a nipple replacing the drain cock at the back of the block (you can add a 90 on that so that you can drain down into a container.) Then do a flush with chemicals designed to break down the scale and rust. The factory shop manual has pretty good descriptions of the cooling system and flushing instructions.

Is it possible you installed the new thermostat backwards? If the radiator has never been cleaned and its original this would be suspect. Can you see the coolant circulating (not bubbling) in the radiator tank when stat opens up? Just installed a 160 thermostat in my 59 last weekend. Lowered reading on the guage by about half from previous 195 stat.

WB is right on the radiator. Have you had it hot tanked, rodded out, pressure and flow checks at a radiator shop? That is sop for any truck I adopt. Hope you have a good radiator shop in your area. They can make or break you. I recently had my gmc re-cored using the original tanks for under $200.

Is the radiator cap, the correct one. Radiator caps hold a certain amount of pressure in the system. Water boils at a higher temperature when under pressure. If its not holding, it will certainly puke out the overflow. And I'd make sure you put the thermostat in correctly. My dad always told me these old sixes would run too hot without a thermostat because the water did not stay on the block long enough.

Here's a quick check for seep leaks at the head gasket- - - -Remove the thermostat housing and the fan belt, and fill the engine up with water until it's level with the thermostat area. Run the engine, and goose the throttle a couple of times before the water in the engine gets too hot due to non-circulation. Bubbles, or coolant forced out of the thermostat casting indicate a pressure leak at the head gasket. From your description of the symptoms, I'm guessing you've got a radiator problem. Back-flushing the radiator helps sometimes, but you're probably going to have to do a rod-out or a recore. To backflush, remove both hoses at the engine, and rig an adapter in the lower hose to let you run a garden hose into the lower hose connection. Run the hose full force, and make the water flow backwards to its normal running direction. If you adapt a blow gun to the lower hose connection, you can also blast compressed air into the lower hose while you're back-flushing, giving the water a shock effect. It's surprising how much crud can be cleaned out of a radiator that appears to be in good shape that way.
Jerry

The symptom you described are that of the air pocket I described. To fill your engine with the funnel (I've used one for years) top off the radiator the best you can and run the engine. As the engine warms up, the anti-freeze will start to rise in the funnel. When it gets about 3/4 full, shut off the engine and let the anti-freeze draw back in. You will also need to add more at this time. Keep doing this a few times until air is out and anti-freeze stops rushing over. I now use a vacuum system that puts a vacuum on the cooling system and draws the anti-freeze in with out air pockets. It will also tell you if you have a leak as in a headgasket. It won't hold a vacuum if there's a leak. Everytime I service my '64 with a 350 in it, I have to purge the air out. Until the thermostat opens and stays open, that air will be trapped. If your head gasket is bad, it shouldn't boil out unless it's very bad. You would smell anti-freeze at the tailpipe and the system would be under high pressure as soon as you capped it. You might still have a gasket problem, but it would be more of a light stream of bubbles at an idle.
Just some food for thought,
Scott

Thanks for all the replys, after much thought I went and bought a new tstat again and found out from "napa" that the old one was the cheapo version of their line. I got a different one this time that looks better made and he says is better. Whatever, I drilled a small hole in it after seeing alot of posts on here about it and asking a few chevy friends. The old one was installed correctly by the way, spring and pellet down needle part up. I also bought a new rad cap as well. It is a 7lb. Also the new tstat is a 160f this time. The sender I bought at napa as well a year ago. It seemed to work ok until now. What is the temp. these 235's overheat? I also know it's not a blown head gasket, it runs fine and has no signs of coolant loss. I'm not going touch the rad. yet, I might try to back flush it later if this doesn't work.

I kinda am leaning towards an air pocket or the cap isn't putting any pressure on the system and it's boiling over to easy. I dunno but I'm tired of this thing getting the best of me I will be testing the old tstat.

I hope it's not a rad. The last rad. shop told me 80 dollars to rod out my old rad. on my 61 chevy and the guy said it leaked after and then wanted 280 to replace the cores and rebuild it. I said ok cause I had no options at the time but I think he took me. It never was the same when it came back, The tanks started to rust in about two weeks cause he crudely sparyed on cheapo black paint. I'll never go back to that place. O yeah it took three weeks too.

hondat,

Use tap water without too many minerals in it if possible. Use distilled water only in the battery. Antifreeze needs some impurities in the water so it can mix properly.

You can check this out with the companies that make antifreeze.

Ok for those still interested, I installed the new tstat and gasket, and rad. cap. It's not overheating anymore and all is well. I know the hole drilled into the new tstat worked cause the old one had no hole and when I pulled it off the engine it was stuck to the hose outlet side and when I actually removed the tstat completely water rushed from the engine side and went everywhere. I think it was air locked. I used the big funnel method and it never blew out like before. I drove it probably 15 miles and it never got hot. The old gauge is terrible though and bounces back and forth but at a dead stop it reads halfway. I felt the hoses and they feel like the same temp. I think it's fixed. I had no idea that these things had such a air pocket problem. Anyways, thanks for the info and help to everyone, great forum!

Next time raise the front of the truck a little so the engine is higher in the front than back. Next fill the engine with a 50/50 mixture with the therm removed. Then put in your therm and button it up. Top off the radiator and start. Raising the front of the engine will decrease the possibility of an air pocket. Finally go to the house for a beer.

Problem solved! Stovebolt attaboy!