Does anyone have this problem of constantly blowing antifreeze out radiator cap when at full throttle? Sounds like to much cavitation from the water pump at higher RPMs which is causing presure to build up in radiator and spray out radiator cap. Either that or exhaust side of head gasket is pressurizing cooling system? I dont think that the latter is likely since compression readings are within 5% tolerance. Has allways done it from day 1 of getting built motor. Any ideas? I am thinking about underdriving the waterpump by 25%...

 

sounds like a blown head gasket. it doesn't have anything to do with exhaust side, it could just be combustion chamber pressure leaking into the cooling system passages. did they machine your deck or heads??? is the truck overheating when this happens? very strange indeed. are they factory head gaskets? I've never heard of a lightning actually "blowing" head gaskets. lifting maybe, but never blowing.

later,
chris

 

Doesnt overheat, or nothing. Hauls *** if anything. Ive put on 3 radiator caps in the last year. As far as the prep work to my heads and block, REM did not do any of your mentioned prep that I know of. They are factory head gaskets with head studs. The tech at Ford told my that it is normal because I have so much horsepower which creates extra heat. Don at Mod Madness told me that its cavitation from my water pump that is putting added pressure in my cooling system...

 

I had the same problem, and the culprit was a head gasket.

 

Even if my oil is free of water?

 

isn't "extra heat" just the same thing as saying "over heating"?

while it's true that increased horsepower will create increased heat and higher demands on the cooling system (may need a larger radiator), this would show on a water temperature guage. if your engine isn't actually running hot, then your extra horsepower isn't the problem. understand what I'm trying to say?

BTW, these trucks were designed to be trucks, i.e. towing another car or boat or hauling a load of whatever, theoretically your cooling system should be up to the demands of quite a bit of increased load or increased horsepower.

how about a cylinder leakdown test, believe it or not, a compression test won't necessarily show a sealing problem.

also you could get your hands on a "block tester" which is a tool that uses a special chemical (I have no idea exactly what it is) and you put it on/over your open radiator (cap off) and it draws air out from the cooling system (sometimes by the aid of an attached engine vacuum hose) it pulls this air through the liquid chemical. this liquid is usually blue in color when it exposed to oxygen. however, when it gets exposed to carbon monoxide (like what would be found in the combustion process it will change to a green or YELLOW color. if you use this tool and it shows carbon monoxide in your cooling system, then you know you have a head gasket or cylinder head or block crack problem. because those are the only ways that that gas could get into your cooling system.

BTW, that would explain why it only happens at WOT (when cylinder pressures are at their highest, they are forcing some air into your cooling system thus causing it to blow air out of your radiator cap.

 

your head gaskets has 3 types of holes in it.

*it has holes for WATER or COOLANT

*it has holes for the PISTONS or COMBUSTION CHAMBERS

*it has holes for OIL

now you could have any one of the things in those holes leaking into any one or more of the other holes.

examples:
you could have water leaking into your oil passages (shows as milky oil or "water emulsion") or you could have water leaking into your combustion chamber (shows up as steam from the tailpipes).

OR you could have oil leaking into your water passages(oil floating around in your radiator) or oil leaking into your combustion chamber ( would likely show as blue smoke from tailpipe or just oil consumption, but highly unlikely due to the pressure difference between the combustion chamber and the oiling system)

OR you could have combustion pressure leaking into either your oiling system (might blow your dipstick out of the tube or oil spraying out of your breather cap or pcv) or you could have what YOU appear to be experiencing which is combustion pressure leaking into your cooling system (which shows up as bubbles in your cooling system, or in the event of a bad leak, it will blow lots of combustion gasses into the cooling system which must escape through the ONLY opening in that system, the radiator cap).

that is why it would APPEAR to be overheating i.e. pushing air/coolant out of the radiator cap, but not showing on the guage as overheating. the water is not really boiling, but air/combustion gasses are being forced into the cooling system by the piston/combustion pressure and they are escaping through the only exit they can find, the radiator cap.

follow me?

later,
chris

 

not to be a smartass, but have you realized yet, that your radiator cap is not the problem?

 

sorry, to keep harping, but think about it. why would your water pump mysteriously start "cavitating" (whatever that means) at the EXACT same time you had your engine rebuilt. the rebuild didn't have any effect on the coolant flow through your cooling system in or around your water pump's impeller did it?

do the math... also, aside from a blown headgasket, you could have an issue with improperly torqued head bolts or studs or weak fastners.

it is common at high boost pressures for factory torque-to-yield head bolts to stretch and the head will actually lift slightly from the cylinder deck surface. this pressure could leak externally (someone had a video of this happening on the dyno) or it could theoretically leak into one of the other cyl head passages.

a similar condition could occur if you had a weak or improperly torqued aftermarket fastner, or if the proper torque sequence (order in which the cyl head bolts are to be tightened) was not followed.

later,
chris

 

Paul at REM kept saying that the Ford caps have allways had problems with blowing, so I kept getting new ones. Also , REM did a chemical test of my antifreeze and it didnt how no indication of combustion gases in my antifreeze....

 

My heads were torqued to 65 ftlbs by REM by accident. Specs from ARP called for 78 ftlbs. So last month, I had my heads all retorqued to 78 ftlbs.

 

I don't know man, but something doesn't add up.

you might have somebody re-test with a block tester.

you'd have to get the engine good and hot and then replicate the conditions that cause the concern.

meaning you'd have to WOT fully load the engine (high combustion pressures, high boost etc) and then immediately test for carbon monoxide in the cooling system.

good luck.

later,
chris

P.S. iv'e worked on a few late model F-150s in my day , and as far as I know, radiator caps are NOT a common weakness.

 

The Ford cooling system is really nice. Cross flow radiator with big aluminum tubes, with radiator cap on low pressure side of the radiator. It's about as nice as one can expect from the factory.

If you were spitting out fluid because of too much horsepower, then that phenomenon would be talked about as much as spitting plugs, clunking suspensions .... etc.

Unfortunatly your problem probably has nothing to do with something as simple as the cooling system

I vote for a slightly blown head gasket.

 

like I said above, improper head torqing. it's possible that the insufficient clamping force due to the under torqing created a leak that could have caused some damaged to the head gasket sealing surface or cylinder head warpage?

 

I had the same thing last year, and it was a head gasket in my case too.