VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Foaming Radiator - 41 Special Deluxe

Okay. I have a new radiator, new hoses, new water pump, new thermostat housing, new thermostat, and new belt. I used Thermocure to clean the rust and gunk out of the block so now the block drain actually runs freely.

But now after I run the car around my little 10-mile test section, I lose up to a gallon of water from the overflow hose on the radiator. Just ran her again and noticed it's foaming like I put bubble bath or something in there (started out as a 50/50 mix of antifreeze and water). I don't see water running from anywhere else on the engine.

What would be causing this? It never did this until after I tried fixing the occasional overheating problem by replacing everything and cleaning the block. And it doesn't do it if I just leave her parked and run her up to temperature - only after taking her out for a drive.

I have a feeling it could be a bad head gasket due to age and previous overheating.

I would suspect a bad head gasket or cracked head.

Like Gene I suspect head gasket or cracked head.
A quick test is to examine the spark plugs, if 1 is cleaner than the rest that is most likely the problem, a little water in the burning process will clean the chamber.
If you can do a cylinder leak test will confirm the issue and which cylinder is the problem.
Tony

Will update this later. Remember the importance of doing ADVANCED SEARCHES of our old posts.

Overheating Issue I am stumped

Good luck, Mike

Actually, Mike, I did search and read that post, among others, before cleaning the block and everything else. I'm fairly certain the block is clean now after running Thermocure in it for a week. All other stuff I tried came out the same color it went in. Thermocure started turning red on the first engine run. It came out filthy black and full of little rust grains when I finally flushed it. And, like I said, the block drain wasn't working at all before. It's running with a good flow now when I drain the block.

That's why, with everything I've done, I'm thinking it's not the cooling system per se, and that's when I started thinking it could be a blown head gasket or cracked head/block. Better be the gasket if anything.

I'm going to check the plugs like TonyW said and start her again this afternoon and watch to see when bubbles/foam start appearing. Will also check the tail pipe for excessive moisture. I don't see anything in the oil. Just want to confirm what's going on before going to all the work of taking the head off, checking for cracks, and replacing the gasket.

Checked the plugs. They are all equally clean - not even any soot/oil buildup on them.

Wiped down the sides of the engine so I could see if there is a leak/crack anywhere. Started her up.

For the first five minutes or so, there were spurts of black moisture from the tail pipe but it was not oily. Figure condensation and carbon. After that first five minutes or so, no more moisture, black or otherwise.

Watched the radiator, occasionally revving the engine. Started getting a little foam but not as much as before. Kept running for 20 minutes. Got more foam but no overflow. Went out and looked again after a few minutes. There is foam in the inlet from the thermostat.

No moisture on the side of the engine. Nothing in the oil.

Is now making me think that I need to run clean water through the engine a couple more times. Maybe there's still some Thermocure or something in there that's causing the foaming. Either that, or there is a small break/crack in the head and/or head gasket. Opinions?

Question: Does the heater/defroster need to be turned on to run water through it? I was assuming the water always ran through it and the heat/defrost is generated by the fan. Wondering if that's where some leftover cleaner may be hiding.

If you did not turn the heater on that may be where the air is coming from.

Yes make sure there is a good flow of coolant through the heater though it may well be big bubbles until there is a good flow through it but will eventually subside from that scource.
If you can pressurize the system try fitting a guage while the engine is running, there will be a increase from cold but should be negligible increase from normal running temp.
Tony

Got her all straightened out, and thankfully it's not a blown head gasket. Though I ordered a complete set just in case. At least I'll have them handy if/when I need them.

Started her up and watched a little foam form. Turned the heater on and got a ton of foam. So that's where it was hiding.

Flushed system twice with clean water and refilled with 50/50 mix with the heater running this time and didn't see a single bubble.

So now I know. When draining the entire system, including the block, refill with both engine AND heater running.

Now, we just need another day or two of good weather so I can take her out again before having to park her for the winter and begin working on the body.

"turning the heater on" with the eletrical switch has nothing to do with the coolant passingthrough the heater core. The coolant is always passing through the core UNLESS YOU HAVE A SHUT-OFF VALVE FOR THE COOLANT.
The eletrical switch merely operates the blower fan.

That's what I was originally thinking.

And yet, when I drained the cooling system this one last time and went to refill it, I started with just 1 gallon. I then started the engine and turned the heater/defrost on. It made a noise I'd never heard before which I took as a pump trying to pump fluid when there was none. As I added the remainder of the 50/50 mix, the noise went away. And, lo-and-behold, not a speck of foam in the radiator.

Like you were saying, I assumed the fluid was always flowing and the switch just controlled the fan. However, the results of what I just did seem to indicate otherwise. Is it possible I have a different type of heater? Mine says "Chevrolet Super Deluxe Heater" on it. Based on everything I've observed, I can only assume it has a fluid shut-off switch connected to the fan.

Well, back to suspecting a head gasket. Thought it was cured but took her out for a drive today and saw the temp climbing. Pulled into the garage and, sure 'nuff, had foam in the radiator again. Though, this time I noticed steam coming from the valve cover. Took the valve cover off and it looks to be coming from the push rod holes - mostly from the center ones.

Still possible head gasket or am I looking at something new?

Might be a crack in the head. If it were mine I would remove the head and take it to a shop and
have the head magi fluxed just to be sure.

BJ,

Try this:

a. Trip the fan belt so the pump doesn't work.

b. Take the thermostat out. Put the housing back on.

c. Fill with water to the top of the housing.

d. Start the engine. Bubbles to gushing of water out the housing indicates compression entering the water jacket. Head gasket, cracked head or cracked block.

If that is all ok then remove the lower hose(s) and fill the radiator with water. Water should't be able to fill the radiator. Hold your hand over the lower outlet and let the radiator bill up. Release you hand and the water should rush out to a height of about five inches and deplete with no significant sucking sound.

I suspect all that block flushing has stopped up the radiator even more than when you started. A good reverse flush may free up enough flues for normal operation but a new radiator, better radiator or core may be the answer.

Good luck with it.

Charlie

Thanks, Charlie. I'll give that sequence a try this weekend (not retired yet so most work relegated to weekends).

I'm still suspecting a blown head gasket. This problem didn't show up until after I had a really bad backfiring problem with the broken rocker arm. And I know bad backfiring can blow a gasket. Had it happen on a lawnmower once - blew a small chunk of the head gasket out.

My heater seems to work fine, but I'll check that out too. Maybe the flow works but is inhibited.

Did as you said, Charlie, for the first steps - took belt off, removed thermostat, added water, ran engine to hot but didn't see a single bubble in the upper thermostat housing. Good news on that is it must not be a cracked anything.

Going to back flush everything again, especially the heater since I'm thinking that may be where the problem is originating. I don't have any leaks and it seems to work fine, but it's the only part of the system that hasn't been back flushed.

One question - does it matter which hose is used for the inlet or outlet for the heater? Just wondering if I didn't mix them up at one point but I'm thinking it shouldn't matter.

The hose location on the heater may indeed make a difference. The hot water from the engine should enter the heater core at the bottom and exit higher up the core. That way any air will quickly be removed. Otherwise air can bleed into the coolant slowly as the flow through the heater core will pickup more as turbulence mixes it in. I am not saying it is the problem but could be. Once the air is removed from the heater core it should cease to be a potential problem.

Thanks! I'll check that. Going to do the whole back flush (block, radiator, heater core) tomorrow. Probably the last decently warm day here in Iowa until next spring.

If all else fails do a pessure teat.

Back flush the engine and radiator separately. May be better to pul the radiator but it is a bit of trouble.

I think that you have plumb stopped up the radiator flues. Now the best you can hope for is to flush out enough flues to sufficiently provide cooling

You may need to have top tank taken off and the core boiled and rodded.

Listen for sucking sound as you release the radiator full of water out the bottom outlet. You should get a good, reasonably tall, rush of water with no sucking sound.

Advice for all: Be careful using flushing chemicals. The top of the flues in the radiator acts as a sieve and will collect a detrimental portion of that gook that gets turned loose.

Good luck, BJ

Charlie