5.0 (306) Heating Issue

[OkieHog]

I have a 90 GT Mustang with a fresh 306 and mods: E-303 cam, Cobra Upper and Lower, aftermarket headers, etc..
The car will not stop overheating!
Blew a head gasket-- fixed-- still overheats.
It naturally has all new hoses.
New aluminum radiator-- Not one of el cheapo models, either.
Naturally, a new water pump.
All components of the cooling system are new.
To give you an idea:
I was going to change the thermostat, again.
I backed the car out from the car-port, turned it around, backed up into the car port, turned it off. Lifted the hood, disconnected the top hose clamp, and it almost blew the hose off, there was so much pressure already built up!

I removed the radiator to see if there was possibly some obstruction. Flows freely.

Here are a couple of things I have pondered:
Obstruction in the block?
Intake manifold gaskets installed wrong? Actually, this was supposed to have been double checked when the original head gasket blew.
Although new, and supposedly for a Fox, could the cross flow radiator be flowing the "wrong way"?
Water pump circulating the wrong direction?

The question is, how do I check the above, especially the later two.

This thing is about to frustrate me....big time!

All help appreciated!

[1gman]

Try filling cooling sysytem with a heater hose off,the higher one,to purge air out of system. When coolant flows out of tube reinstall hose.top off rad to about 2nd row,then start car without rad cap on. Coolant level should drop about half of coolant tank,BE CAREFULL STAND ASIDE OF RAD OPENING,slowly add coolant, if you have bubbling/gurgling or worst case coolant spewing out of rad you've got compression going into coolant passage
Did you have the heads checked for cracks?,
Did engine overheat,or did it run long without coolant?
Al

[racerxmdd]

Sounds like you have a air bubble in the system. What does the oil dip stick or breather look like?

[scottyM]

Head gaskets installed correctly?

[bmcdaniel]

Originally Posted by scottyM

Head gaskets installed correctly?

That was my first thought.

[Farrit]

Seems like all the people who have problems with their mustangs all have the cobra intake it is a bad intake to buy so it kinda lets you know who your dealing with when reading the questions about their cars.

[OkieHog]

Originally Posted by Farrit

Seems like all the people who have problems with their mustangs all have the cobra intake it is a bad intake to buy so it kinda lets you know who your dealing with when reading the questions about their cars.

That is interesting. Had not heard that about the Cobra Intakes.

Heads were checked-- double checked.
Head gaskets were changed by a certified mechanic, so, I thinking that it must be block. If you start the car with the rad cap off, it pushes water out, big time. Pulses with the stroke of the engine.

[scottyM]

water pump wrong direction flow?I wonder if you should disconnect your heater core until you fix this, seeing as they seem to be a weak link.Thermostat?What brand?You could temporarily remove it.

[1gman]

ouch thats not a good sign! looks like the heads will be coming off again

[AlexLTDLX]

Originally Posted by OkieHog

Head gaskets were changed by a certified mechanic,

Hate to say it, but that's probably the problem right there. When he changed the gaskets, did he check the deck/heads for flatness? If it blew a headgasket before (why?) that's one of the things that I would definitely check. Did he at least glance at the bores? Certified or not, I'd bet money that he screwed something up. If it's pushing water out, it's most likely the headgaskets; it'd have to be one helluva crack in the block to do that. Find another mechanic (or better yet, do it yourself - we'll all help you if you've never done it before). That way you know it'll be done right. Then get your money back.

[scottyM]

Ive had a 302 push water out like a guyser before, from air.I would say unlikely though.