Help! Rocketeers and motor guy in general. Exploding radiator!

Ok, first of all Im not a poet or writer and Im sure Ill misspell some words. I have a punched out olds motor with some work done to it. I had a problem with the system building presure in the radiator and blowing a 18 psi cap under acceleration. The radiator is a 3 core 66 mustang radiator. Now ive run this radiator for three years with no problems but have blown a few holes in this motor and thought it might be cloged so i replaced it. It did the same thing with the new one. So I diagnosed by a radiator presure tester a quick rise in presure and found a blown drivers headgasket which i had suspected from some visable moisture. So i replaced it was blown.

Took it out last night let it warm up good to bring the oil presure down. Does fine under normal driving conditions. Stoped and did a full 4000 launch and in two seconds she started flowing like a gieser the whole time the pedals down. Tempeture never went above 180. But in 1/8 mile full out i lost probably close to a gallon of water. I checked the water pump before i replaced the radiator. its intact.
Kanter rebuild piece that i had to weld the day i got it but thats another story. I pulled the plugs after i got back they were dry so headgasket held.

Is there another way im getting compresion into the system or is this radiator not able to handle this motor. Im at a loss

 

ok... so you did a hard launch, noticed it was haemorrhaging coolant, and never lifted... ok i kinda see where you're comming from

anyhow,

from where was the coolant coming? head gasket? pump? hose? rad?

 

You got a thermostat in that thing ?-MIKE

 

You've got to realize I've been dealing with this for over a month. I'm a little over the whole car getting washed with water. The temp stays cool the oil presures fine the roads straight ! Anyway the water is coming out the cap overcoming the entire cap. I've put four caps on it. Overflow is atached. Even driving 70 down the highway it will start pushing water out. Drive it normal and it's fine. Put it under load and it starts. No other leaks. I'm not running a thermastat right now cause of all the issues I've had with them but it does it either way

 

I also tried to restrict some flow when I did have it out with a drilled plate still did it. Normal therm, highflow therm I've tried it all

 

You can have a high frequency compression leak from the cylinder to the water jacket without water in the cylinder or oil. I suggest you put the pressure tester back on the radiator with 0 pressure and run the engine up. If it pressures up you still have a compression leak. If you do I suggest you remove the heads and check the surface to make sure there flat and or take them to a machine shop for pressure testing and while there in the shop clean and inspect the deck of the motor.

 

Sounds like the radiator core will not flow as much coolant as the water pump puts out at high RPM. You could try putting a restricter in the top radiator hose to slow down the coolant flow. I did this on a 32 Hupmobile I had and it cured the problem. Or put a bigger pulley on the water pump to slow the rpm of the impeller.

 

What is the rad out of? Old rads don't like 18 lb caps. The tanks weren't designed for that kind of pressure. Pat.

 

66 mustang rad.

So it should never build up to 18 right?

I used a SO straight bar to check the deck and block they were good. This is a pretty heavly worked over 346 prob 11+ compresion. Bigger exhaust valves ported.

 

I'm suspected another comp leak just don't want it to be true so looking for something I could have missed. There is no water in the oil or oil I'm the rad

 

I would also look very closely at the exhaust ports since they were ported. Could have nicked a water jacket on the exhaust side and under normal driving it would burn off a little coolant probably not even noticeable. Then under hard acceleration with backpressure the reverse happens and you pressurize the cooling system.

like what one of the other guys said, probably going to need to get them pressure checked.

 

Is your upper hose or any other part of your cooling system higher up than the radiator cap?

If so,you couid be developing some major air pockets in the system.

If that`s the case,you can try to install a bleeder or a remote filler cap.

 

I put the presure tester on and let the motor warm upfor five minutes. The presure slowly rose up to 15 psi every pump of the throttle picked it up. I then reved the motor three times each time raising the prsure up to 21 under revs it would go down two or three then climb higher after back to idle. I believe I could continue to grow presure but stoped at 23.

 

Take the cap off and let the engine run and see if your getting air bubbles in the coolant. You should see coolant movement with no thermostat but no air bubbles. Then give it some gas and keep looking to see if you ever get air bubbles in the tank. Sounds like a cracked head or block to me.

 

Napa can supply you with a block checker for a few bucks. It will tell you if you are getting combustion products into the cooling system. If you are, there's a leak somewhere. If there isn't, your looking at a coolant delivery problem, but that's not likely unless you have a severely restricted radiator.

 

Ok I will get the napa tester. I'm pretty sure I'm leaking compresion into the coolant.

Next ? there might not be time for me to fix this by the 22. I'm thinking of running a closed water system, no raditor with a water tank located in front with a presure release sytem to feed a tank in the back to be able to make some p***es. Push to the line. Make a run and refill the system. Do u guys think this could be possible?

 

I bought the tester will check it tonite. This is prob what it is if so I bet it's my drivers side that had the blown head gasket. The other side has always been dry.

 

Well i did the test last night. Thank the hotrod gods no combustion in the radiator.

What i did to diagnose 1/2" hole in a washer in the thermastat housing to slow down the flow. i also tightened down the cap ears which pushed the top down tighter.

Bottom line the radiator can not keep up with the flow and heat. so im ordering a walker today. i will probably get two row 1 1/2" or what the suggest will be best. thanks for all the help looks like i should have her all ****oned up unless i blow it up first!

 

Never seen a water pump create 21 LB. of instant pressure but Good luck

 

See post #7

 

This type of problem will drive you CRAZY !! I have chased **** like this until it made me pull my hair out. The only way I've been able to track a leak like this is as follows. Warm up the engine to 190*,remove all of the spark plugs, remove all of the rocker arms, do a leak-down test on each cylinder with 150# of air,watch for bubbles in the radiator as each cylinder is tested,when bubbles appear Presto you've found the cylinder that's giving you the trouble. Then it's another game to figure out what is actually leaking !! I hope this helps >>>>.

 

You said the temp never got over 180, so it's not a heat issue. You said it pumps up 21 lbs of pressure with or without a thermostat, so it's not a flow issue. Doesn't sound like a radiator problem. Did you look for air bubbles in the coolant with the cap off? I've never seen an engine with a new radiator that builds 21 lbs of pressure at 180 degrees. I don't think it's the radiator.

 

did you not see the thankyou..

the presure build up is in the top of the rad tank. With the cap off and the water just sitting on the tubes it flows freely at 1500 rpm. raise the rpm to 2500 and the level starts to rise to the top of the tank. 3200 and it starts to flow out the top. The presure is created because the water can't get through the tubes.

 

Sounds like either your radiator is clogged and creating artificial pressure, or there's a head gasket leak.

Put your nose down in that radiator and smell for gas & exhaust, it's more sensitive than a pressure tester. If you're leaking past the head gasket, there's already enough fuel in the antifreeze that it'll stink.

good luck

 

I'm with this guy

 

^
One thing to remember with the backpressure theory. The actual backpressure.

Data point.....LT1 caprice with 2 1/8 duals with factory bends that go down to 1 7/8, manifolds, dual cats, dual quiet mufflers, dual resonators. Basically something that hushes 280 horse down to a level acceptable for bluehairs.......They develop around 14 to 15 psi in the manifolds.

Basically I'm wondering if there's actually enough pressure differential to push exhaust into the cooling system. My understanding is most performance exhaust develops more like 6-8psi backpressure, which is not going to be overcoming the pressure in your radiator.

I hate disagreeing with Rich Fox. Only a matter of moments til I'm proven wrong

Good luck!

 

You may be right. I had the same experiance in years past BUT it was a turbocharged GMC. Had a crack in the exhaust port that didn't open up until it got hot. Back pressure would be much greater driving turbos hard I am sure. But that thing would split the seams in any radiator I tried. However, Shifity may very well be right. Without the turbos maybe it wouldn't have happened. Would have been a boring ride though. PS I wouldn't want to dissagree with Squirel or Bruce Lancaster. Those guys know thier stuff. Dissagree with me and you have at least a 50-50 chance

 

ok fellas, you know i dont want it to be a cracked head but i went ahead and did the combustion test again this time even revving the motor to help simulate the time when the pressure happens but not enough to plug the tester. I saw no signs of yellow if anything a dark green blue. I also smelled per a sugestion my sniffer ****s but couldnt tell. So i am ordering a walker 4 core z radiator tomorrow. 4 row 1/2", 1/4" spacing. $650 Ouch! Lucky for me the ford set up work great for a olds, Top center bottom drivers. Im hoping its flow, if not i needed this rad just never wanted to afford it. Remeber my mustang is a three row 1/2", 1/2" spacing.

I hope it works thanks for the help! And to all those that think is combustion its still right in the back of my mind i just am hoping its not true. Thanks guys see ya at the drags!!!!

 

This should prove to be interesting (sorry it had to happen though).
The performance rad over the Mustang unit will not be a waist of money, good investment...as it sounds like your making some HP.
I could see hot exhaust super heating the water and producing the pressure above normal...

 

Sorry to post again, but just a thought.
Couldn't you pull the fan belt to isolate the water pump and start the engine and observe the coolant level without it being masked by the water pump flow? If it happens to be a cracked block/head gasket, then it would become pretty obvious almost right away, wouldn't it? If there are no bubbles or serious movement in the tank then it would answer your question/problem almost immediately.