Overheating after shut off

[fyreduck1921]

Hey everyone,

I hope someone can help me out. I have a 76 Bronco Sport with a 302 and C4. I've had the Bronco since last August and have put about 3,000 miles on it in that time. The previous owner only had the truck about 3 years and had taken it as payment for a debt, so he knew very little about it. Based on the idle, I believe that it has a mild cam in it. He told me that he knows the heads are from an earlier year (71?) because the spark plugs from a 76 didn't fit. The truck also has an Edelbrock Performer intake and 4 barrlel carb.

Under normal conditions, in town or on the highway, the truck runs at 190*F according to the factory temp gage. When I come to a stop, the truck maintains that temperature. When I turn the Bronco off, then turn the key back ON (so the gages work) the temperature quickly climbs all of the way to the peg on the hot side. If I start the truck with the temperature elevated above about 220*F on the gage, it is noticeably harder to start, and runs rough until the temperature comes back down to 190*F. The temp comes back down pretty quickly once the truck is running.

I have not flushed the cooling system, but the coolant looks to be in good shape; clean and green.

Am I damaging the truck by letting it get this hot?
What are the potential causes and solutions?

Thanks in advance for any thoughts.

Steve

 

[MarkBright'67]

Hi fyreduck , I think the problem could be fixed changin' the rad cap , Good Luck ! 

 

[miesk5]

Yo Steve,

Does the Bronco have an electric cooling fan?

Overheating cracks head gaskets & allow non-compressible water into the cylinders thus and can distort cylinder heads & other parts.

 

[Bully Bob]

1st., It's perfectly normal for all water cooled engines to heat beyond normal after shutdown.

This is simply due to the fact that the water is no longer moving, & the heat is not being pulled from the block.

However, under normal conditions your truck should run at 180 deg.

Trusting these older gages is not a good idea. Meaning you're possibly runn'n at some point higher than a steady

190deg.  (Harbor Frt. has laser guns on sale---approx $35)

First thing I'd do is R&R the thermostat. In doing so, check the number on it. If it's above 180, get a new 180.

It cools down quickly so water pump & radiator are likely in good shape.

Timing could be off. This can cause heating issues. Too much adv. can cause hard start.

There's a slight chance the altered cam comes into play here.

Don't know what to make of the spark plug holes.... sounds like aftermarket heads.

Double check that. And does this appear to be a stock early 302 or a later model.?  Check the #'s on the block

by the starter.

Lastly, see if you can get more info. from previous owners.

 

[69bronc347]

OK read the post all the way through. There are a few possibilities here, like bully bob said the temp will rise when shut off, but I don't believe that much. I believe what you have going on is a improperly maintained cooling system. You say the coolant looks good but I believe there is years up build up in the block and heads acting as a thermal barrier. Once the engine is shut off the coolant is now able to extract the heat from the engine. OR there is no thermostat in the vehicle and is allowing the coolant to pass through too fast and not pick up enough heat. If you want an idea of actual engine temp, get a reading of the oil temp. Engine oil temp give a more accurate reading of actual engine temperature. Engine oil temp should be no more than 10 degrees higher than coolant temp. Good luck Steve and let us know what you came up with.