The Stovebolt Site Forums The Shop Area Engine Shop Help with Overheating problem (1952 GMC 228)

It's been 5+ years since I flushed the cooling system on my '52 GMC 228.

I bought 2 gallons of antifreeze, 2 gallons of distilled water and 5 pounds of citric acid powder.

Parked the truck nose down about a foot in the driveway and then drained the old coolant into a 5 gallon bucket. Got about 4 gallons as expected.

Connected the garden hose to the "flush fitting" I put into the return hose from the heater the last time I flushed the system.

Removed the thermostat and put the thermostat housing and upper radiator hose back in place. Left the drain cocks in the lower rear of the block and in the lower radiator hose open and the radiator cap off.

Cracked open the temp sensor fitting at the rear of the head to allow air to escape. GMC engines are known to run hottest at the rear of the head. When I bought this truck it had modern aftermarket gauges that sort of looked like stock, but were very hard to read accurately, especially oil pressure and coolant temp. So I installed a 270 degree sweep mechanical temp gauge at the rear of the head and moved the electric gauge's sender to the engine side of thermostat housing. Historically, the gauge in the head has read about 10 degrees hotter than the gauge in the thermostat housing.

(This is paragraph A) Refilled the cooling system with just water from the garden hose, then adjusted the hose flow until it barely overflowed at the radiator filler. Fiddled with the drain cock at the rear of the block any time it would partially clog. Let the hose run like this for 10-15 minutes. Then started the engine at about 1000 rpm and let it run another 15 minutes with the hose flow adjusted to keep a slight overflow out of the radiator filler. Shut the engine off. Allowed the system to drain all the way down and repeated this paragraph one more time.

Closed all drains, mixed the citric acid with 5 gallons of water and filled the cooling system. "Burped" the temp sensor at the rear of the head until only liquid came out, then tightened it up.

Drove the truck for about a week. Never got over about 170 degrees (A/C on, 90F air temp, NO thermostat). Maybe 100 miles total. The longest was 30 miles to the dump to dispose of the old coolant.

Drained the citric acid mixture and did the flush with water routine as noted in paragraph A above.

Drilled a 1/8" hole in the flange of a new 160 degree thermostat and installed it. Closed all drains, mixed the 2 gallons of antifreeze with 2 gallons of water and filled the cooling system. "Burped" the temp sensor at the rear of the head until only liquid came out, then tightened it up.

Then started the engine at about 1000 rpm and let it run. "Burped" the temp sensor at the rear of the head again. Checked both the coolant temp gauges after 2 minutes. They were both starting to register. Started picking up tools. Felt the upper radiator hose. It was starting to get warm. The next time I looked at the temp gauges the electric temp gauge it read about 150-160 degrees. The mechanical gauge at the rear of the head read 230 degrees and climbing!

Shut the engine down, said a bunch of words I wouldn't have said if my mother was standing there, cried a bit and gave up for the day.

In my mind only 2 things can be wrong.
1. I put the thermostat in upside down. I do know the difference.
2. The thermostat was defective when installed.

This morning I took the thermostat out. It had been installed in the proper direction. Then I suspended it in a pot of water on the kitchen stove and warmed it up, testing the water temp with a cooking thermometer. It started to open at 162 degrees and was completely open at 170 degrees. It is stamped 160F.

What now, oh temple of knowledge, aka 'Bolters?????

1) Have you tested that mechanical gauge against another one, on the same sample? Or perhaps just test it against a thermometer of some sort. My first inclination is bogus result from a bogus gauge.

2) That coolant port near the back of the head is very near to the exhaust manifold. Perhaps it is picking up some radiant heat from that area. It shouldn’t behave that way. Still evidence of a bogus gauge, just a slight twist on the failure mode of bogus-ness.

230 degree coolant on a low pressure system should be been boiling like nobody’s business. My bet is that your system is working as it should.

Bill, sorry to hear this. The 228 I had 40 or so years ago was doing the same thing. It turned out the whole back side of the number 6 cylinder was full of old junk. Couldn't see of course but I suspect it may have been a couple of inches deep. Since I didn't want to pull the engine I drained all the coolant, removed the water pump and made a long tool out of a coat hanger. Just straightened it and bent sort of an L shape at the end. Then I worked it all the way back to the rear and jerked it back and forth and twisted it around to dislodge as much of the crud as possible. I tell you about this to save you the trouble.

Then frustrated that wasn't working as well as I hoped I got one of the cheap spring-like plumbing snakes and I worked it in and back there. It was the one that had a spring diameter of about 1/4"...not the heavier 1/2 or 5/8" one the plumbers use. It was much more effective at twirling around and it broke up much more junk in the process. Still wasn't easy, however. I was at an angle and flushing with a garden hose out the water pump opening. I did this for most of an afternoon and then I jacked it up so it would lean backwards and poured some stuff I got at the auto parts store (which was sold as rust dissolver) in there and let it sit for a couple of days. Then I got the plumbing snake and repeated all that action I mentioned earlier. After that it ran normally again.

When I had this same problem with my 235 about 6 years ago I did the same thing but I didn't have that plumbing snake any longer so I poured CLR straight in there and let it sit for 2 days. Drained it out, neutralized with soda and repeated two more times. Finally I was able to break up enough to get it flushed out okay. Good luck.

If it is suspected there is crud built up back there, couldn't you have better access through a freeze plug?

Yes, but you have to pull the engine, remove the transmission, clutch, pressure plate and bell housing to get access to that freeze plug.

A GMC has five freeze plugs down the driver's side of the block. Pull the intake/exhaust manifold assembly and remove those plugs. That will give you a clear shot at the bottom of the water jacket for a detailed cleaning. Replace the press-in plugs with the rubber expansion type that bolt in.
Jerry

But the engine did not have this overheat problem before I started the flush and refill. Nor did it overheat while I drove it 100 miles with the citric acid flush and no thermostat in the cooling system.

Plan for later today is to drain the antifreeze mix, remove the thermostat and refill with just water. That should take me back to the conditions I had last with no overheating. While I'm at it, I'll pull the sensing bulb from the rear of the head and test the mechanical gauge against my cooking thermometer.

By the way, the radiator has a 7# cap, which should raise the boiling point of 50/50 antifreeze mix to 245F.

On my original flushing with water and later citric acid the coolant drain at #6 cylinder new did "clog up" so much that it stopped draining. Mostly just slowed down a bit and gentle twisting of the handle would resume "full flow".

I use a laser type temp gun pretty frequently to check different places on the block, the cylinder head, the thermostat housing, and the radiator to monitor how well the temperature is distributed in the cooling system. A localized hot spot indicates low or maybe no coolant flow in that area.
Jerry

Good idea Jerry. I have one in a kitchen drawer. I'll drag it out and see if I can gain any additional information.

It could be as simple as an air pocket at the sensing bulb, that would be a spot that steam would be pushing the temperature above the water temperature.

I "burped" the sensor by slightly loosening the sensor until just coolant (no bubbles) flowed out around the threads.


It will be tomorrow before I can get back to working on it. 6:20 PM here, with a 96 degree air temp and the truck is on the west side of the garage. Too darn hot.

If your infrared thermometer verifies that the temp is really 230, I'd suspect that the coolant flush washed a bunch of crud into a bottleneck area and stopped up the coolant flow.

Of course verify the coolant temp at the T stat and upper radiator hose outlet.

As stated above, I "burped" the sensing bulb until I had liquid come out by slightly loosening the nut on the tube that holds the bulb in place. I checked it a number of times while running to make sure it was still immersed in coolant.

Update this morning.

By the way, the coolant is Walmart house brand ethylene glycol that I mixed 50/50 with distilled water. Color when new is kind of [censored] yellow. When I drained the antifreeze/water mix
last night I ran it into a non-transparent container. This morning I decided to pour some through a clean white rag to see if there were any large chunks of rust or whatever in the mix.

Found 2 interesting things.

The color of the mix now has a definite dark brown coloring when you are looking through more than an inch of liquid in a clear glass container. After 3 or 4 inches a light will not shine through the mix. Looking at the color through the clear plastic radiator catch can hose (5/16" ID) it was closer to yellow, but still had a brown tinge to it and you can see small "blobs" of the slime in the hose. If you drain the hose much of the slime remains in the hose until forced out with a water stream from my garden hose. The clean white rag that I poured the coolant through was yellow and had small amounts of the same "slime" in it. There were no "chunks" of material caught in the rag.

The upper part of the thermostat housing (where the top radiator hose attaches) was left on my workbench overnight. It also had some of that "slime" noted above in it. When I looked at it this morning the inside had dried leaving behind a yellow (antifreeze colored) powder deposit. The deposit rubs of easily with just a touch of my finger.

I also tested the accuracy of the mechanical temp gauge (the one at the rear of the head). I boiled a pot of water and immersed the bulb (after wiping a small amount of that same slime from it) in the pot. By the time I got the pot from the stove in the house to the garage 100+ feet away and sitting steady under the hood my IR thermometer measured the water temp at 186 degrees and the truck's mechanical temp gauge read it at 193 degrees. Not exactly equal, but not so far off that the 230 degree reading I had yesterday morning was just instrument error. I gotta believe the engine was really hot.

Question: Could the "slime" be the result of insufficient rinsing after using the 1 pound of citric acid per gallon of water flush mix? I have used this method before (in another truck as well as this one) and did not experience slime.

Plan for the rest of the morning is getting the truck's nose pointed downhill to drain as much more of the coolant out. I may even try blowing through the radiator filler with my shop vac to get as much more of the coolant mix out as I can.

Then back to draining the system by running the garden hose into the running engine with all draincocks open and enough flow to slightly overflow the radiator.
Question: Should I do this with or without the thermostat in place? If you answer, please state why you have that opinion.

You could take one of those really strong, rare earth magnets and see if your “slime” will stick.

You’re actually just a step ahead of me doing something fairly similar. I bought some muritatic acid (for rust) and TSP (for greasy deposits) based on a procedure HRL recommended here some time ago. My coolant (green) has turned pretty awful looking and it’s very much time to do a big flush.

I have some ideas about adapting some small diameter hose to barb fittings in both the block and radiator drains to make a multi-step flushing a lot easier and provide means for some compressed air blasts both directions.

I’m actually curious about the thermostat question you raised. I hadn’t planned on removing mine. Mine does have the hole drilled in it already.

I'm in the process of flushing the block now. Been doing it with the engine running for about 20 minutes. Petcock at the rear of the block and bottom of the radiator open, radiator cap off, flush hose attached to the fitting in the return heater hose going into the water pump. Adjusted the flush hose flow so radiator filler (highest point in the system) overflows slightly.

I'm leaving to go to the gym in 30 minutes. Before leaving I will turn off the engine and adjust the garden hose flow to barely overflow the radiator. Wont be home for 2 hours, at which time I'll start the engine again.

I'll probably use the old thermostat just for giggles the next time I install one.

Does the water running out look like it's bringing crud with it? I think that slime is what's clogging up the works.

I'll be curious. Aside from crud at the lower back of the 6th cylinder (which might or might not be the case here) "stuff" blocking the tubes in the radiator is what I'd say might be the next in line of problems. If you disturb things those can get clogged and that'll be a problem. Thermostats? I've had two fail. The new you you have wasn't sold under the name "Fail Safe," was it?

Fail Safe! I wonder if it was made by the same company that made the SELD-M-BREAK hydraulic hose for the Springfield monorail?

Engine has been flushed for 3+ hours now with the engine off, no thermostat, drains open at the bottom of the radiator, the rear of the block and radiator cap removed. Just enough flow from the garden hose to cause overflow from the radiator filler. Now that I'm home I started the engine and adjusted the garden hose flow to maintain slight overflow from the radiator filler.

I'll let it run like that for an hour or so. Then shut off the engine and garden hose flow. Wait for the system to drain down, close the drains, refill with water only, burp the rear temp sensor to clear air from the system and start driving it around the neighborhood.

After 30 minutes of running in 99F air temp with constant flow from the garden hose, the back temp gauge is reading about 140 degrees and the front temp gauge is about 130 degrees.

NAPA #60 thermostat, but it is stamped MOTORAD 0323.

Maybe, but Homer might like this more...the Fail Safe thermostat is a really interesting design. If your engine ever overheats, the thermostat locks open...fully open. To get it to work again you have to remove it and use needle-nosed pliers to try to extract the gizmo that has just disabled it without ruining the whole she-bang. Actually there are two. One diametrically opposed from the other one. Very special.

As you see, you now have no thermostat whatsoever and you may not be able to figure out what is wrong with your cooling system and why it has suddenly gone all wonky. Rube Goldberg at his finest and proof that if P. T. Barnum said "there's a sucker born every minute" he understood the business plan of the Fail Safe company.

When I realized what a poor design it was I never installed the one I bought. A friend however said he learned the hard way if you have anything floating around in your cooling system it can lock the thermostat shut causing your engine to constantly overheat until you remove and discard it. That's why I ask the question.

0323 isn't the Fail-Safe, but the Fail-Safe was either bought by or started by Motorad.

Bill, what you reckon the slime was? Just some residue from the flushing process?

An hour + later ...

Refill with water only, burp the rear temp sensor to clear air from the system and start driving it around the neighborhood. 100F air temp. No thermostat.

Engine temp stabilized at 178F at the rear of the head after about 1.5 miles of driving. The rear gauge had been tested earlier and found to read about 7 degrees high between 180 and 190, so this 178 indicated was more like 172 real. Front temp gauge read somewhere around 170.

Drove a total of 4 miles and neither temp gauge changed a bit. When I turned the engine off the rear (mechanical) gauge peaked up to about 192-195. This truck has always done that.

Plan now is for another trip tomorrow morning, maybe 10 miles or so. If that goes well I'll put in a thermostat (probably the old one) and test some more. If THAT goes well, maybe put in new antifreeze over the weekend.

I'm kind of up against a deadline here. The truck is supposed to represent the Gillespie County Historical Society in the 4th of July parade next week with a bunch of kids riding in the back and the Big Kahuna of the GCHS riding shotgun. But I won't risk a breakdown or overheat during the parade.

Just a suggestion Bill, but I don't think a lot would be hurt by running water and a little anti-freeze (to discourage rust) with no thermostat. Could you just do that until after the parade and then start chasing the problem again?

When I drained the old coolant I didn't notice the slime. Then I flushed the system using a pound of citric acid powder per 1 gallon of water. I've used this mix in the past and never had a problem. I don't recall seeing the slime when I drained the citric acid mix and flushed with water. The slime showed up when I added the new antifreeze. I'm guessing that I didn't properly flush with water the citric acid mix and that it reacted with the antifreeze, producing the slime.

JonG:

Assuming all other testing goes well, I think I'll try your plan for the parade. I might even do a "dummy parade" here in the subdivision to test the system.

A dummy parade sounds like an ideal plan, Bill. That way you'd know there would be no surprises. I suspect it is hot down your way. Here the thi has been incredible. 108~109 today and they say the same for tomorrow. Hope the parade will be early and passing through some tree-lined streets!

I used Google Earth to measure the parade route at 2.24 miles. Total length of one "lap" in my neighborhood is 4 miles. The parade kicks off at 10am, but I think I'll use hotter 4 pm as my test.

We haven't had your kind of heat yet Jon. 101F at 5:25PM yesterday was the high for the year so far.

After an acid flush, I use a box of baking soda dissolved in water to neutralize the acid. Then I follow up with a strong TSP/water flush to take care of any greasy deposits the acid doesn't remove. One more water flush, and then add a 50/50 antifreeze/water mix. A 50% solution has a freeze protection of -37 degrees F. and it preserves rubber parts better than straight water.

DO NOT run straight antifreeze. It does not transfer heat well, and it gets slushy at +9 degrees F. An 80% antifreeze 20% water mix should be the absolute strongest solution to run. A little water in the mix is required to kick off the proper freeze protection.
Jerry

Jerry:
I've got the baking soda and will use it soon (I hope, see next post). What mix ratio?

What ratio is a "strong TSP/water flush"? Local ACE hardware has TSP in 4 pound tubs.

The cooling system holds almost 4 gallons. I used 2 gallons of antifreeze along with 2 gallons of distilled water to start this whole mess.

Went out this morning to clean out the radiator overflow bottle that I forgot to clean yesterday. It has been unhooked for 2 days, so no chance of "slime reinfection" during yesterday's testing.

I left the cooling system full last night with the radiator cap on and tight. When I took it off this morning there was some evidence of the yellow slime on the top of the water under the radiator cap. Not a lot, but some. Maybe 3 or 4 globs, each less that 1/8" diameter.

I turned the cap over and found additional slime there. Didn't get a picture of that, but the picture below shows the slime on the radiator cap an hour later as the water dries out. It is about 1/2 dry. The slime coagulates into small pieces and when totally dry is a yellow powder (same color as the antifreeze) and can be easily brushed off any surface.

So I started the flush with water routine again, sometimes running, sometimes not.

When I get home this afternoon and it cools down a bit (say 8pm) I'll do the baking soda flush next.

Now that I look at the picture of the radiator cap close up, it looks like I need a new one. Cracks in the rubber at 2 o'clock.

I'm assuming the "box" is the common 1 pound box. I have a 13.5 pound bag that I'll take some from. Maybe 2 pounds for my 4 gallon cooling system.

I bought a 4 pound tub of TSP today, but I'm still waiting for a definition of

By the way, with the 300+ gallons of well water at 7.2 pH that I've run through this thing the last 2 days I'll bet the acid is all gone. Still going to run 2 pounds of baking soda in it overnight.

Put in the 2 pounds of baking soda and 4 gallons of water about 6pm. Let it run for about an hour in the driveway. Temp stabilized at around 165 in the thermostat housing (still no thermostat installed) and 170 at the rear of the head at a fast idle. Then adjusted the idle speed to give 4 mph in 2nd gear of my SM420 transmission. Let the idle speed get me to the gate out of the subdivision, just under 1 mile, simulating parade speed. The temperature may have varied 5 degrees max. Air temp was 94 to 92 degrees.

I'm planning to leave the baking soda in the truck overnight, then crank it up for an hour of idling in the morning. Then another slow trip out of the subdivision followed by 10 miles or so of 40-60 mph driving.

Hopefully Jerry will check in with a recipe for the TSP flush by then.

Sounds like a good scheme, Bill. I think we're supposed to have a heat index of 115 today. All the man-made lakes that ring DFW make sure our humidity stays close to what you might enjoy in New Orleans.

Do you have a coolant recovery tank? Nice that you have a water well!

Yes

Bill, after the parade and the dust settles on you cooling system project, consider installing a coolant filter. You can use a remote filter base and a couple of METAL quarter turn valves and plumb it all into the heater circuit. Wix makes spin on filters with sacrificial zinc sized for various engines. I think the part number I used was a Dodge/Cummins application. Under the radiator cap inspections shows squeeky clean tubes after 2 years and 10,000 miles.