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

 

 

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

 

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.

 

also check the timing to retarded will make it want to overheat too

 

I spinned the blade and it did have resistance, checked the oil and no foamy, milky oil just dirty

 

how do I check the timing on this? How do I post a photo

 

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/

 

[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

 

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.

 

Checked all the hoses the guy I bought it from didn't mention anything about maintenance, he bought it and resold it. How do I check for wrong timing I think that may be it, I checked the radiator but does not leak, could not find a single leak.

 

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!!!

 

great thanks I'll remove that tomorrow and buy a new one. When a radiator is clogged does it get hot or stays cold??

 

 

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.

 

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.

 

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.

 

 

ok got it, when I shut off the engine it smokes a little like burning oil out of the valve covers what do you think that is?

 

It could be that, oil leaking out from under the valve covers and getting on the hot engine. Do you see oil leaking out? Is the smoke coming from that area? This should be pretty easy to spot. If you do, replace the valve cover gaskets, and make sure the valve cover bolts are tightened in a "star" pattern and to the correct torque.

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.

 

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.

 

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

 

 

ok flushed the radiator filled it back up and rode it and noticed when it started to overheat opened the cap and the coolant I filled it up to was gone but no leaks what so ever can't figure it out no leaks but losing coolant what can it be

 

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

 

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?

 

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.

 

Oldcutlass nailed it ^^^^^^^^^ do as he mentioned.

 

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

 

ok will try that now

 

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?

 

no was not pushing coolant It has a stock 17psi cap

 

Let us know how its going after you do what Oldcutlass suggested.

 

You need to use something like this to flush the engine and radiator.

 

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.