bad head gasket = pressurized rad ?

denns1989

denns1989

Member
My 8BA was rebuilt in early 60's, hasn't ran since 1970 - just got it in shape to actully run for more than a few seconds, I have flushed the block, replaced water pumps with speedway unit's, installed 160 thermostats -previous owner was running with no thermostats so I discovered (I'm well aware about the million opinions on thermostats, no thermostats, washers/restrictors etc) I also had the radiator flushed, repaired & tested, installed new rad hoses... Previous owner had a 13lb cap which I replaced with a new 4 lb cap as I understand that 13 lb is a bit excessive in most circumstances for these engines.
The first time I had it running with coolant I had a little bit come out the overflow, but it had been running for a few minutes & didn't think much about it, however the next few times I had it running I noticed more coming out of the overflow, my initial thoughts were that maybe the overflow port was below the rad cap seal (I had never really paid attention), basically working as a non pressurized system like my wifes Model T & it was just finding it's happy level... but I checked & the overflow is above the rad cap seal... so I started wondering what can make that kind of pressure in the cooling system if the coolant isn't even warm yet...
There is no "sweet" smell to the exhaust, the oil isn't milky & no visual leaks on the engine... I'm assuming it's possible that the head gasket is failed & cylinder pressure is pushing the coolant out ? I plan on pressurizing the cylinders & see if I get some bubbling in the coolant but wanted to check with people that know much more than I to see if I'm thinking straight :-)

Thanks in advance, sorry for the long description.
 
What's the longest run time you had? My new rebuild violently erupted the first run-up. I blamed it on trapped air. Filled it back up without thermostats and it had the typical overflow. Put a coolant recovery tank on it and everything has been good.
 
You've got a good plan. You can do a valve/ring/gasket leakdown check all at the same time. Remember to be on TDC and be careful to stay away from engine driven parts.

Lonnie
 
flushing the radiator if its plugged is useless, you need to have it rodded out, these old radiators like the water down about an 1 1/2"s, just above the radiator cores, the rest will be spit out, a parcially plug radiator will cause water to be lost, the water is being returned to the radiator faster than it can be sent back to the engine, run a compression check, all readings should be about 5# of each other, if exhaust pressure is getting into the radiator there will be water coming out the tail pipe, a blown head gasket into the water jackets will cause those plugs to be real white with no carbon on them
 
Compression check for fun, will explain a lot if done properly. What's the rad level. Is it really low? How's the engine heat on start up? Put a infrared gun on it don't rely on a gauge. Couple easy things to check.


Is this a stock raditor and engine?
 
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Check and make sure the bottom of the pressure cap is seating down on the seat washer about an inch down in the neck, most don't. A thin rubber washer down on the seat will do the trick. If you had a compression leak and a 13 lb cap I think you would see a puffed up tank or other signs of damage. With a working pressure cap you can run the water up near the top of the tank, more coolant in the system and more flow through the system equals better cooling. G.M.
 
Tony said:
What's the longest run time you had?
Click to expand...

Aside from the first time I was filing the cooling system it was probably running around 10 minutes, most other times 5 minutes or less, I was wondering about an air lock, I understand sometimes people drill a small hole in the thermostat to let the air out ?

Thanks all for the other ideas, I will takes these ideas & continue the investigation !
 
My 34 FWIW will idle forever it seems with no issues and when I drive her it runs cool for about 20 minutes then it heats up (looking at the temp gauge) quickly and within another couple of minutes it is boiling. I've tried everything, with help from folks here, without any significant change. My next move is to remove the heads and check for cracks in either the heads and/or block.

I'll be following this thread for possible additional ideas. Good luck.
 
I had a similar problem with I installed a 8BA in my 41 pickup. After trying several things I figured out I was filling the Radiator too full. I found you just need to cover the core. If you fill it to the neck the coolant will go out the overflow. I stopped overfilling and haven't had a problem since. The engine does not overheat. Hope this helps, it worked for me.:)
 
carguybill said:
My 34 FWIW will idle forever it seems with no issues and when I drive her it runs cool for about 20 minutes then it heats up (looking at the temp gauge) quickly and within another couple of minutes it is boiling. I've tried everything, with help from folks here, without any significant change. My next move is to remove the heads and check for cracks in either the heads and/or block.

I'll be following this thread for possible additional ideas. Good luck.
Click to expand...

Carguy, Try to find the problem before pulling the heads. If it is a crack you would have one of the following, water in the oil, a lot of water out the exhaust pipe or compression pressure in the radiator. No water in the oil or not a lot out the exhaust lets look for compression in the water. Take radiator hose off the top at the radiator leaving them on the water pumps. Remove the fan belt, fill the hoses up to the top so you can see the water good. Start the engine and look and look to see if you have bubbles. You can run for a few minutes before it gets hot. No bubbles and it is unlikely you have a crack or a blown head gasket. I would say you are loosing to much coolant out of the overflow, try Skips 3 LB valve on the bottom of the overflow tube. To test cooling it is best done in your driveway as the conditions are the same all of the time. When testing put a large electric house fan AGAINST the center of the grill turned on high speed. It is best to have a laser pointed temperature gun. The left and right side of the block are not connected in the block but are separate water systems only connected in the radiator. Take temperatures every 5 minutes on the hump on both heads 1/2" behind where the pump bolts on and write them down. I run the engine at a speed of about 20 MPH. Not having the 3 lb valve you could put a rubber or plastic hose on the bottom of the overflow tube and put something like a plastic pen in the bottom end of the hose to keep the water from just backing out the tank. As long as the engine temperature don't get much over 200 there will be less than 2 lbs pressure and as long as the pen isn't in to tight it will blow out from exhaust or compression pressure. I went to a car show once and had the same problem with low water and over heating. Put the pen it the overflow, filled the radiator and drove home with no problem. Added Skips 3 lb valve and never had any trouble after that. I had a picture of the pen sticking out the over flow hose but I just looked and it disappeared. G.M.
 
Allright, things are looking up.
I drilled a small vent hole in each thermostat & filled the block before installing the thermostats (I know redundant, but I thought I might as well), then just topped it off to cover the top of the cores, fired it up & no more boil over !! Seems it was one heck of an air lock.
Also during my investigation I discovered my rad is out of a Henry J ! with extra ports added to fit the flathead, 4 lb cap and so far so good !

Ohh yes also did a compression test after it was warmed up & with throttle wide open during compression test.

#1 Cyl - 98
#2 Cyl - 102
#3 Cyl - 105
#4 Cyl - 105
#5 Cyl - 105
#6 Cyl - 108
#7 Cyl - 110
#8 Cyl - 100

Considering the car wasn't ran since 1970, was lightly siezed when I got it last summer & I have had it running only a few times for a few minutes at a time, I think those are some decent numbers the worst (98) is still in range of the best (110) I believe, at least close :-)

Thanks again for the advice
 
Sounds like you did good. 15 percent is he usual rule of thumb for variability between cylinders, and you are with in that range already. As posted many times here and other places, change the oil and filter a couple of times, put some Marvel Mystery oil in the crankcase and the gas tank and drizzle a little down the carb and make some smoke. It looks like things can only get better from here

I had stored my '51 for 5 years in the 90's and it didn't run for squat when I finally got it out, with a couple of cylinders in the 80's. A little TLC and all was well. The worst thing you can do is let these things sit for any period of time.
 
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