67 Bonneville Overheating

[ellev8or]

V8 6.6L 400cib
59000 mls

I've installed a new intake manifold and gaskets about a month ago and was wondering can a vehicle suffer overheating from faulty intake gaskets or intake manifold?

I've also installed new radiator, water pump, hoses and thermostat; it is overheating. There is no white smoke or fluids dripping from the exhaust. The radiator fluid has been spewing out like a volcano when I drive for about 15 minutes. Could it be my radiator cap; it feels loose? I've just learned that thermostats have certain temperature limits for the cooling systems and was wondering if that could be a factor.

Your valued assistance is greatly appreciated.

[oldblu65]

Originally Posted by ellev8or

V8 6.6L 400cib
59000 mls

I've installed a new intake manifold and gaskets about a month ago and was wondering can a vehicle suffer overheating from faulty intake gaskets or intake manifold?

I've also installed new radiator, water pump, hoses and thermostat; it is overheating. There is no white smoke or fluids dripping from the exhaust. The radiator fluid has been spewing out like a volcano when I drive for about 15 minutes. Could it be my radiator cap; it feels loose? I've just learned that thermostats have certain temperature limits for the cooling systems and was wondering if that could be a factor.

Your valued assistance is greatly appreciated.

Take your radiator cap to you local parts store and see if they have equipment to pressure test your radiator cap . The cap should not be loose when installed properly so if the new one does - it may be defective ? The thermostats are rated by temperature and it will be stamped on the unit itself . The most common ones are 160 degrees , 180 degrees , and 195 degrees ! Late model vehicles generally run the higher temperature rated units as the emission systems require the higher temps ! Keep us updated - good luck !

[maxwedge]

Thermostat in upside down? Do the hoses pressurize quickly right after starting?

[ellev8or]

@ maxwedge: the thermostat is in properly-spring downward. I'm not certain if the hoses are pressurizing after starting but after idling or driving for 15-20 minutes around town, the temp starts to rise. If I'm on the hwy doing about 50 mph or higher the temp lingers at 200 degrees for about 10-15 miles, then it shoots up to 240-280 degrees. I've changed the van clutch also.

@ oldblu65: I've tried several new caps-all different-and they all are loose. The test proves that they are good. As for the thermostat, I took the car into an a/c repair shop and they replaced the original thermostat of 195 degrees with one of 165 degrees. They stated it should be a lower degree thermostat to maintain coolness in the system. I found that to be backwards since the block is a V8. Am I wrong?

Oh, does it matter if there's a noticeable loss of power? Like its difficult to accelerate-I have to push the pedal to the floor.

Thanks for the advice gentlemen.

[maxwedge]

Wow lots of issues here, without a loss of coolant or vapor out the tailpipe it would be very unlikely if the head gaskets were bad. These engines never had a 195 t'stat, they used 180. Does the coolant cross flow thru the intake, if so, maybe the intake gaskets are in wrong. Advanced or retarded timing can also cause this, restricted exhaust can cause overheating and loss of power, this is going to take a lot of diagnosis for a complex problem or lots of money will be spent with guesswork. If a 400 block cannot accelerate easily something is radically wrong, I would address the loss of power first, any misfire, coolant on the plugs?

[oldblu65]

Originally Posted by maxwedge

Wow lots of issues here, without a loss of coolant or vapor out the tailpipe it would be very unlikely if the head gaskets were bad. These engines never had a 195 t'stat, they used 180. Does the coolant cross flow thru the intake, if so, maybe the intake gaskets are in wrong. Advanced or retarded timing can also cause this, restricted exhaust can cause overheating and loss of power, this is going to take a lot of diagnosis for a complex problem or lots of money will be spent with guesswork. If a 400 block cannot accelerate easily something is radically wrong, I would address the loss of power first, any misfire, coolant on the plugs?

Could the fact that this engine was ( supposedly ? ) a reverse flow cooling system ( cooling water went from the top radiator hose to the heads first , then down to the block , then back to radiator through the bottom hose) have any affect on this problem ? I'm not particularly familiar with this setup so I don't know what affect this might have ? Could this have caused confusion in the reassembly of the engine perhaps causing a mis-step ?

[maxwedge]

Reverse flow would require a different water pump, I would get a shop manual here and look into this but it still does not explain the loss of power.