455 oveheating
#1
455 oveheating
hello guys just bought a 73 pontiac gran prix sj with a 7.5 455, changed the thermostat to a 160° bought new upper and lower hoses, takes a bit of time to overheat now it got to 220 it's a stock engine really need some advice on how to fix it please help
#2
pontiac motor?
Check the usual suspects:
is radiator clean and no debris blocking air flow through it?
fan clutch good ( if it has one)?
is radiator fan shroud in place?
have you flushed the cooling system?
timing set right?
does it get hot idling or running down the road?
is radiator clean and no debris blocking air flow through it?
fan clutch good ( if it has one)?
is radiator fan shroud in place?
have you flushed the cooling system?
timing set right?
does it get hot idling or running down the road?
#3
yes it a pontiac engine, radiator is clean, how do I check If the fan clutch is good? It has the fan shroud it gets hot when running down the road when I turn it off it smoke out of valve covers. Sorry I'm new to these engine
#4
With motor off spin the fan blade and it should stop pretty quick, two or three turns. If it spins freely it may need replaced.
Check the oil and look for foam on the dip stick. If white foamy oil then you may have head gasket issue. Probably not but rule it out.
Check the oil and look for foam on the dip stick. If white foamy oil then you may have head gasket issue. Probably not but rule it out.
#6
I spinned the blade and it did have resistance, checked the oil and no foamy, milky oil just dirty
#8
1. The thermostat temperature has no bearing on the final operating temperature of an engine. It only controls how quickly it gets there.
2. 220F is not the temperature of an overheating engine. The boiling temperature of a 50/50 water/antifreeze mixture is well over 250F at 15 psig. You are worrying about nothing.
https://www.cars.com/articles/should...1420680334271/
#9
[QUOTE=jaunty75;1111669]1. The thermostat temperature has no bearing on the final operating temperature of an engine. It only controls how quickly it gets there.
2. 220F is not the temperature of an overheating engine. The boiling temperature of a 50/50 water/antifreeze mixture is well over 250F at 15 psig. You are worrying about nothing.
ok so I ran the car yesterday and the max temperature It got to was 220° while cruising down the highway when i stopped at a red light the temperature started to go up to 240° and shut the engine off what's up with that?? When I shut the engine off it sounded like it was boiling but it wasn't
2. 220F is not the temperature of an overheating engine. The boiling temperature of a 50/50 water/antifreeze mixture is well over 250F at 15 psig. You are worrying about nothing.
ok so I ran the car yesterday and the max temperature It got to was 220° while cruising down the highway when i stopped at a red light the temperature started to go up to 240° and shut the engine off what's up with that?? When I shut the engine off it sounded like it was boiling but it wasn't
#10
You didn't mention 240F in your earlier post. That is an issue. You need to check the various causes (wrong timing, clogged radiator or hoses, malfunctioning fan clutch, etc.) that have been suggested.
You say you just got the car. Do you know anything about its prior maintenance history with regard to the cooling system? The radiator should be removed and be checked by a competent radiator shop. The full system should be thoroughly flushed.
You say you just got the car. Do you know anything about its prior maintenance history with regard to the cooling system? The radiator should be removed and be checked by a competent radiator shop. The full system should be thoroughly flushed.
#11
You didn't mention 240F in your earlier post. That is an issue. You need to check the various causes (wrong timing, clogged radiator or hoses, malfunctioning fan clutch, etc.) that have been suggested.
You say you just got the car. Do you know anything about its prior maintenance history with regard to the cooling system? The radiator should be removed and be checked by a competent radiator shop. The full system should be thoroughly flushed.
You say you just got the car. Do you know anything about its prior maintenance history with regard to the cooling system? The radiator should be removed and be checked by a competent radiator shop. The full system should be thoroughly flushed.
#12
Using a handheld point and measure thermometer, confirm the accuracy of the temperature gauge. Then use it to check the radiator core externally for cold spots. A cold spot shows a blockage internally in the radiator. A slowly climbing while cruising temperature is often a blocked radiator core which does not cleanup with a routine flush. The radiator needs to have the tubes professionally rodded or the core replaced.
Good luck!!!
Good luck!!!
#13
Using a handheld point and measure thermometer, confirm the accuracy of the temperature gauge. Then use it to check the radiator core externally for cold spots. A cold spot shows a blockage internally in the radiator. A slowly climbing while cruising temperature is often a blocked radiator core which does not cleanup with a routine flush. The radiator needs to have the tubes professionally rodded or the core replaced.
Good luck!!!
Good luck!!!
#15
Why do you think the timing is the culprit? It would be one the of the last things I'd suspect, but it is easy to check. If you don't know how, I would first suggest finding a good youtube video. You will need a timing light and you will need to locate the timing marks on the harmonic balancer. The timing light will come with instructions on how to hook it up.
Here's one video on the subject. There are many others. Most of the ones I find talk about Chevy engines, but it works the same for Oldsmobile, although you rotate an Olds distributor in the opposite direction from a Chevy distributor. But you'd notice that the first time you rotate it.
Here's one video on the subject. There are many others. Most of the ones I find talk about Chevy engines, but it works the same for Oldsmobile, although you rotate an Olds distributor in the opposite direction from a Chevy distributor. But you'd notice that the first time you rotate it.
#16
If a radiator is partly clogged, then the parts that are clogged are not seeing any fluid movement through them, and thus those parts of the radiator are not contributing to the cooling of the engine. Those parts of the radiator will be cooler than the parts where coolant is circulating, but the total effect is that the radiator is not cooling the fluid as efficiently as it should because the total heat transfer surface area is less than it should be. The coolant will therefore not be cooled as much as it should be as it passes through the radiator, so the engine will run hot.
#17
Remove what?
I think you misunderstand what Sugarbear is saying. He's not telling you to remove anything from the engine. He's telling you to buy one of these, which Amazon sells for about $10. Use it to measure the temperature of the engine at various locations and confirm the values you read off of the gauge.
I think you misunderstand what Sugarbear is saying. He's not telling you to remove anything from the engine. He's telling you to buy one of these, which Amazon sells for about $10. Use it to measure the temperature of the engine at various locations and confirm the values you read off of the gauge.
#18
Remove what?
I think you misunderstand what Sugarbear is saying. He's not telling you to remove anything from the engine. He's telling you to buy one of these, which Amazon sells for about $10. Use it to measure the temperature of the engine at various locations and confirm the values you read off of the gauge.
https://www.amazon.com/dp/B07DDCY4JH...aa_pcomp_aapi1
ok thanks I was just going to remove the radiator and throw in a new one because the one it has is old I thought if it's not the timing it has to be the radiator or maybe the water pump or cap
I think you misunderstand what Sugarbear is saying. He's not telling you to remove anything from the engine. He's telling you to buy one of these, which Amazon sells for about $10. Use it to measure the temperature of the engine at various locations and confirm the values you read off of the gauge.
https://www.amazon.com/dp/B07DDCY4JH...aa_pcomp_aapi1
ok thanks I was just going to remove the radiator and throw in a new one because the one it has is old I thought if it's not the timing it has to be the radiator or maybe the water pump or cap
#19
If a radiator is partly clogged, then the parts that are clogged are not seeing any fluid movement through them, and thus those parts of the radiator are not contributing to the cooling of the engine. Those parts of the radiator will be cooler than the parts where coolant is circulating, but the total effect is that the radiator is not cooling the fluid as efficiently as it should because the total heat transfer surface area is less than it should be. The coolant will therefore not be cooled as much as it should be as it passes through the radiator, so the engine will run hot.
#20
Also, if it is a leak from the valve cover, it's probably smoking all the time, but you only notice it when you've shut the engine off and thus aren't driving down the highway and blowing the smoke away.
#21
Dang unlucky week for 455s, having the exact same issues as you! I am begging for a good oldsmobile in my area to take it to as it is past my limited skills. If I get a fix will be sure to pass along here.
#22
I would take the rad cap off, drain some coolant out from the drain **** until its about 1 " above the trans cooler .
1st check to see how the tubes look.. Corrosion around the tubes. Overall condition of the rad fins..rotted, loose.
Fire up the car and let it run for a good 10 minutes on high idle until the t-stat opens, you should see flow through the rad. Poor flow will just be dribbling out the tubes....
This ^^^^ will give you a good indication as to what's going on with your cooling system.
Process of elimination after that.
T-stat
Water Pump
Hoses
Rad
Hope this helps,
Eric
1st check to see how the tubes look.. Corrosion around the tubes. Overall condition of the rad fins..rotted, loose.
Fire up the car and let it run for a good 10 minutes on high idle until the t-stat opens, you should see flow through the rad. Poor flow will just be dribbling out the tubes....
This ^^^^ will give you a good indication as to what's going on with your cooling system.
Process of elimination after that.
T-stat
Water Pump
Hoses
Rad
Hope this helps,
Eric
#23
My car had the wrong water pump on it. Was for non a/c car and I had a/c. If there are numbers on the body of your pump check with a parts store to see if it's correct. Before spending tons of money throwing parts at it follow the suggestions above. I threw parts at mine not even suspecting the water pump being wrong.
#24
My car had the wrong water pump on it. Was for non a/c car and I had a/c. If there are numbers on the body of your pump check with a parts store to see if it's correct. Before spending tons of money throwing parts at it follow the suggestions above. I threw parts at mine not even suspecting the water pump being wrong.
#25
ok thanks a lot having a lot of trouble here to even find someone who knows these old engines lmk asap if you find out the problem
#26
How did you flush and fill the rad ?
What happened when you pulled the rad cap off after it was about to overheat?
Do you have an overflow bottle? If so how much coolant was in it?
#27
It may have just burped some air pockets and the level dropped. Fill it again, start the engine with the cap off and wait for the thermostat to open, coolant will start to flow and the level will drop again. With the engine running fill the radiator 1-2" from the bottom of the neck and put the cap back on.
#29
I removed lower hose put my water hose in the upper engine block for 5min refilled it with new coolant and started it ran for 10min and started to get close to 220 removed cap off just let pressure out, yes it has a overflow bottle it was heating up to, was smoking out of a little hose
#30
It may have just burped some air pockets and the level dropped. Fill it again, start the engine with the cap off and wait for the thermostat to open, coolant will start to flow and the level will drop again. With the engine running fill the radiator 1-2" from the bottom of the neck and put the cap back on.
#31
Was the system pushing coolant into the overflow bottle while climbing to 220? If their was an air lock, it would have pushed coolant into the overflow, purging itself. Then pulling coolant back as needed while lowering the temp on its own.
What PSI cap are you using?
What PSI cap are you using?
#32
no was not pushing coolant It has a stock 17psi cap
#35
If the radiator is badly clogged with scale flushing and rodding are unlikely to have much affect. Replace or recore the radiator if you find seting the timing correctly doesn't fix it.
You are describing the classic symptoms of a plugged radiator, and they don't last forever.
Roger.
You are describing the classic symptoms of a plugged radiator, and they don't last forever.
Roger.
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