overheating

[mark71]

I've got 1971 bronco stock 302. While driving on HYWY for 20-30 min, then in town temp starts to climb to 200-210. While letting it cool down with engine off, 5-10 min later radiator starts to leak from cap. I have replaced cap twice, new thermostat 190, temp sensor, and have had radiator cleaned "boiled". Any suggestions why overheating?

 

[Seabronc]

Welcome to the Zone > .

Have you had this truck? Have you done a good system flush to clean the crap out of the engine block? It could be that there is so much crap in it that it doesn't transfer heat very well.

In town driving, (slow, stop and go traffic), is when you need flow in the system the most and also when it is the least efficient. I assume that you have a stock fan on it, (which may have fan clutch problems), and a fan shroud. In either case the fan doesn't draw air across the radiator fins efficiently.

The leaking when you shut off the engine is probably from the water temperature surge that occurs when the engine has been running and is then shut down. Since the temperature is already high it surges to till it is right on the edge of boil over. Fix the other problem and this one will go away.

Good luck,

>-

 

[mark71]

Welcome to the Zone > .

Have you had this truck? Have you done a good system flush to clean the crap out of the engine block? It could be that there is so much crap in it that it doesn't transfer heat very well.

In town driving, (slow, stop and go traffic), is when you need flow in the system the most and also when it is the least efficient. I assume that you have a stock fan on it, (which may have fan clutch problems), and a fan shroud. In either case the fan doesn't draw air across the radiator fins efficiently.

The leaking when you shut off the engine is probably from the water temperature surge that occurs when the engine has been running and is then shut down. Since the temperature is already high it surges to till it is right on the edge of boil over. Fix the other problem and this one will go away.

Good luck,

>-

 

[mark71]

Thanks for the reply. I Bought it about 1 yr ago, the motor was rebuilt "They said" 3000 miles ago haven't had any problems until now. Love the truck, lots of fun. I'll try the flush see if it works? Had a 74 Bronco about 15yrs ago liked so much had to get another.

Thanks Again.

 

[MUZZALL]

I had a simmular problem when I bought my 68. It turned out that the head bolts were loose (20-35 ft/lb) and my head gaskets failed BAD.

 

[mark71]

I had a simmular problem when I bought my 68. It turned out that the head bolts were loose (20-35 ft/lb) and my head gaskets failed BAD.

Hey, not to sound stupid, but all you needed to do is tighten up the bolts?

 

[MUZZALL]

If the head bolts are loose, and the gasket is leaking the gasket is probably shot. I would check the torque on the head bolts, check for oil, fuel in your coolant, coolant in your oil, and/or white smoke in your exhaust before changing your gaskets.

 

[Bully Bob]

Mark..,

1.) Do you NOT have a coolant recovery bottle..? Rad. cap is designed to relieve press. (into a reservoir)

2.) What are you gauging that temp. (200-210) by..?

 

[Bronc76]

Check ignition timing.

 

[Bully Bob]

Also., I forgot....

What RU using as a mixture ratio for your coolant..?

---- AND-----

190deg. is too high for the older eng.'s go with 180 & don't use the "CHINA" auto parts on this item.

(I've seen new ones that don't work.)

Try NAPPA or a quality parts store.

 

[chase8266]

I've got 1971 bronco stock 302. While driving on HYWY for 20-30 min, then in town temp starts to climb to 200-210. While letting it cool down with engine off, 5-10 min later radiator starts to leak from cap. I have replaced cap twice, new thermostat 190, temp sensor, and have had radiator cleaned "boiled". Any suggestions why overheating?

if you have an after market intake manifold it needs to have a water crossover in the rear otherwise it will run hot just like the 351w.they do make a manifold with a water crossover or you can drill an tap