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Discussion Starter #1
This problem has been buggin me for a while now. I don't get it, my radiator always overflows and the engine never gets hot. It seems no matter how long you let it cool when you open the rad cap it releases a ton of pressure along with a ton of antifreeze (not even hot).

13 psi cap, overflow level with top of rad, modine alluminum rad tested by a local shop before use.

:(
 

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Brandon said:
This problem has been buggin me for a while now. I don't get it, my radiator always overflows and the engine never gets hot. It seems no matter how long you let it cool when you open the rad cap it releases a ton of pressure along with a ton of antifreeze (not even hot).

13 psi cap, overflow level with top of rad, modine alluminum rad tested by a local shop before use.

:(
How about a bad head gasket? Checked for combustion gases in the coolant? Are you SURE that the engine is not running hot? The coolant is either expanding from heat or is being pressurized by gasses being forced into the system from somewhere. Just my 2 cents.
 

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they make a neat little kit you can get at any pro auto parts store.. you put a fluid in a glass that has a rubber gasket that you put over the radiator opening.. have some one rev it up alittle and draw some of the vapor in with a pump.. If there is combustion in the vapor it will turn a certain color.. i have not used mine for a few years but it worked good for me..
 

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Brandon said:
how could I test that?
If you know anybody with a 4 gas analyser just have the radiator open and hold the sniffer close to the opening.Ensure that you do not pick up any coolant by mistake.Maybe even drain some out to prevent a problem.If you see anything over 60-100 hc you may have the beginnings of a head leak or crack.You may want to examine your plugs as well looking for unusually clean ones.
 

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I had the same problem, it was a blown HG. I went by a smog shop and the guy used the sniffer to confirm the problem.
 

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Discussion Starter #8
zags said:
Have you tried a new radiator cap?
yep

I guess I'll take it to a shop - can they tell which head and any idea how fun it is to change a head gasket on a 5.0?
 

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Brandon said:


yep

I guess I'll take it to a shop - can they tell which head and any idea how fun it is to change a head gasket on a 5.0?
I'd think a cylinder leak down test would show which cylinder.

As far as changing the head gasket... remove brackets on front of engine, distributor (place engine @ TDC and mark dist/rotor location - should be @ #1), intake manifold, exhaust manifold on the offending side, valve cover, remove push rods (keep in order), and finally the head. After that you need to check out what has been going on. I'd have the head checked to make sure it isn't warped or cracked. Clean everything up and put back together following factory specs/procedures. Very important to find out where exactly it is leaking and deal with any problems so it doesn't start leaking again.

Hope it turns out well for you.
 

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its gotta be a headgasket. I had the same thing going on for a good while and couldnt figure out what the hell it was. Then one day going down the road i looked back and i couldnt see anything for all ther smoke. The gaket finally blew out and the cylider was getting filled with water. Long story short it was a blown headgaket. I bought some nice high $$ felpros this time...cause i dont want to have to del with the shit again. so far so good
 

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My buddies 88 Mustang 5.0 did the exact same thing. One of the head bolts sheard off right at the head. Pulled the heads and after a fresh set of gaskets and new head bolts he was good to go.

Sounds like a head gasket problem.
 

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Discussion Starter #12
It was fine all day and I have a 13psi cap - I'll try a 16 and see if that does the trick..
 

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Be careful stepping up the PSI on the cap... If you get a cap rated too high for your system you'll cause way more problems. You'll get leaks everywhere!

The PO of my brothers Scout had a 13psi cap on it and it leaked everywhere, overflowed all the time - you could read the reciepts in the glove box like a bad story... He raked up over $1000.00 in mechanics/tow truck bills just due to the cap (idiot!!) he ended up selling it because he thought it was just plain fawked. A new 7psi cap and it runs fine even on hottest days in CA.

Anyway - run a cap rated for your system don't go too high and blow holes in everything.
 

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Discussion Starter #14
the last two shops I asked both said use a 16 so that is why I was gonna try that.. It is a 5.0 with a large modine alluminum radiator
 

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Brandon said:
the last two shops I asked both said use a 16 so that is why I was gonna try that.. It is a 5.0 with a large modine alluminum radiator
Is there a HEATER CORE?

Yes, older vehicle designed for 4 psi radiator cap. A friend put in a 13 psi cap "since it had a new radiator" Heater core split a seam and dumped the fluid! :(

Why are you opening the cap when the engine is HOT? Fluid does expand when hot, hence overflow tanks!

Blown head gasket test. Remove cap. Start engine. Let it warm up... look for a stream of little air bubbles coming up throught the coolant. Pretty simple.

As to which bank... uh, best to replace them both. :) Usually when I first get the air bubbles in the radiator... compression test and leak down test are fine. Takes a while for the gasket to finally blow enough to make a difference on the compression test. SOMETIMES during the leakdown test on a warm motor I'll get the air bubbles up through the radiator....

Tom :usa:
 
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