94 Ford Mustang Cobra overheating

N2COATING

MEMBER
1994 FORD MUSTANG

I recently rebuilt (302) motor. I had heads surfaced and pressured checked also surfaced lower intake. I used cometics head gaskets and fel-pro for all other gaskets. The car will idle and run fine until I get on it hard it pushes coolant out into overflow and then starts to overheat. I've did a combustion leak test on it and the dye showed no clue of blown or craked heads. Also I have checked thermo and water pump. I took radiator out and took to radiator shop they said flow was very good. I put new 16, lb cap on it. I also checked timing, collasped hoses, also checked the fan and it is working properly. I posted this on horsepower junkies and no one can figure it out. I'm willing to try anything to get this fixed.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Not all cracked heads or cracked blocks will show up in a chemical check. Sometimes cracks only show up when pushed hard like you discribe. Try checking the water pump for proper rotation.

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Friday, February 16th, 2007 AT 2:48 PM

INDYUKE

MECHANIC
416 POSTS

I had the same problem once. I've found that the head gaskets on the 302 motors are not mirror images from left to right. On the driver's side, the head gasket goes right side up, with the "front" sign and the arrow showing and the tabs up. The passenger side must be placed on upside down, with the "front" sign and the arrow (while still being on the front) against the block with the tabs up. I've done it wrong, and while the cylinder holes line up, coolant holes do not. It re-routes the coolant right past the head.

I may be way off base, but that was the first thing I thought of, especially since you've checked pretty much everything else. I hope this helps.