Posted by Charlie (IP: 171.215.149.216) on January 16, 2000 at 20:48:31:
In Reply to: proper temp? posted by Erik on January 14, 2000 at 20:46:35:
I hate to say so, Erik, but you have a blown head gasket or cracked head (302 heads rarely crack, probably just a gasket). Here is my diagnosis:
The tempurature wavering is because the tempurature sender is coming in and out of water. When not in contact with water, the sender reads low. Your real tempurature is 240, but when you step on the gas the cylinder pressure rises (exhaust backpressure rises too). Because of the leak, it forces this pressure into the cooling system, pushing gas past the fuel sender causing it to lose contact with coolant and read lower than normal.
This increased pressure is forcing the radiator cap to release (it releases above 13 lbs) and coolant is discharged.
When going over 60, (or just pressing on the gas), RPM's & backpressure are increased and the problem occurs.
You have a major problem, unfortunatley. Bring it to a mechanic shop and have them do a coolant leak test. Also, have them run the engine with the tester hooked up. I am sure the pressure will rise above 13 lbs. If so, I am correct.
Head gaskets on 302's aren't hard, but it happened for a reason. Maybe the head was cracked to begin with, or the engine overheated for some reason, causing the gasket to fail. Some mechanic shops "break in" an engine by running it without coolant for a short time. Why, I dont know. This can cause head gasket failure.
Keep us posted.
-Charlie
: What is the proper temperature for a 302, my motor is getting slowly broken in but every once in a while my temp goes up to 230-240 if I step on it or go over 60 but then once it hits that temp it just shoots back down to 180, is there some sort of problem?