lvsmustangs

Hello everyone my 1992 f 150 302 5sp completely stock runs fine for about 15 to 20 min then blows the coolant out the overflow box extremely violent full on steaming and bubbling. I've put a new cap on it and a new thermostat and i can see the water circulating in the fill neck. I had a leak about 2mo ago and didn't see exactly where it is coming from so the worst move i did was pour 2 bottles of bars leak i know bad move. My question is can a clogged heater core make this happen or a partially blocked radiator??? I'm thinking the head gasket might also be bad. The truck runs great and still has excellent power and acceleration. I noticed my heat died down after i poured the bars in also. Any help would be appreciated.

Rusty but trusty

well, that doesn't sound good. Im not a fan of a fix in a bottle. If you want to rule out the heater core just unhook the two hoses from the fire wall and hook them together, now the heater core is not in the picture. To me it sounds like you have a blown head gasket/cracked head/cracked block and its over pressurizing the coolant system. Go to the parts store and rent a coolant pressure tester, See if your system holds pressure.

Or... when the engine is cold, remove the radiator cap, start the truck, rev the engine.... If your garage ceiling is painted with coolant then you probably need to tear the engine apart.

lvsmustangs

Good idea with the hoses for the heater core gonna give that a try right now. If that doesn't work I guess I'm gonna have to do some wrenching. The water will rise up a little if i step on it, but it hasn't shot up like a geiser yet lol. Thanks for your time!!!!

Rusty but trusty

N/P, I would advise doing a leak down test before ripping the engine apart. Your lower hose isn't collapsed right? Also, when the truck is up to temp both heater core hoses and both radiator hoses should be warm. If one is hot and one is cold then you don't have flow.

lvsmustangs

Just tried the heater hose switch and same thing. My top hose gets extremely hard and seems really pressurized really hot compared to the bottom one. The hoses that go to the heater core where full of all kinds of gunk and yesterday i noticed one was hotter than the other. I'm gonna give it a rest tonight and let things cool and tomorrow pull the thermostat and see how it does without it. It runs cool and then just gradually it builds pressure and pushes the coolant out maybe my radiator is partially blocked and can't flow the coolant. If it's not the radiator i have plans to find a 96-97 explorer and just swap out motors the local junk yard has em for 140 bucs. Not trying to use the intake and all the sensor garbage though going to carb it and hei distributor route so at least that is a upgrade to roller and gt-40 heads. Oh Boy this is gonna be a fun journey.

Rusty but trusty

Ok, now it sounds like the radiator may be clogged up with that stuff you poured in. The upper and lower hoses really shouldn't feel all that different in terms of pressure. With the upper and lower hoses unhooked, pour a gallon of water in the upper hose and see how long it takes to come out the lower? Just an idea. Trying to prevent you chucking unneeded $$$ at it.

flareside crazy

I had this happen to me replaced my fan clutch and it was smooth sailing from there

lvsmustangs

Thanks for that idea also, but no luck as soon as i poured the water in it came right out the bottom at least that is a good thing the radiator isn't clogged. At least where eliminating the obvious factors and if i wouldn't of had some inputs i probably would have just bought new parts right away. I'm on a budget also.

lvsmustangs

Okay flareside gonna try and find some information on how to troubleshoot my clutch fan and take a look at some electric fans at advanced auto. I think In my truck it has a 2g alt don't know if that's enough to run electric fans. I had a 90 302 mustang 5sp with ac and it had electric fans from the guy before me but I could tell the alt wasn't strong enough never had a dead battery but i could tell if i drove at night with lights on or in daytime when ac was going. The adventure continues

lvsmustangs

well back to the drawing board the electric fan helped but i don't think it's big enough it's a 16" and pulls 1400 cfm and across the radiator 1150 cfm it took 35 min to overheat and when pulling out it went up and then cooled after 50 mph . the fan is just crazy loud also.