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1994 Cadillac Seville SLS
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63 Posts
Discussion Starter #1
Its weird, my caddy starts overheating when im in the hwy, it gets to over 240 then when i let go of the gas, and just let it ride for a bit, it starts to go down, and thats when i start to gas it a bit and it starts going up again. When i let it go, the temp goes to about 228.

In streets my car gets no hotter than 219. What can this be?
 

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1997 SLS
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550 Posts
Afterburn - any codes? Also, how old is the coolant? Have you checked the overflow tank (WHEN COLD)? What is the condition of the water pump belt (right side)? Are there any leaks on your garage/driveway under the engine? As many have said here, good coolant maintenance is key to a Northstar's survival.
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
Get a combustion byproducts test done on your coolant to see if it's a headgasket problem.... Other than that, check for leaks, check the waterpump belt and tensioner, and make sure the purge line is flowing freely.
 

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1994 Cadillac Seville SLS
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63 Posts
Discussion Starter #4
No headgasket problem, thats for sure.
No leaks or signs of leaks.
Belt is tight but not too tight.
Water pump is running nicely.

Cooland in other hand is bad, been in there for as long as i had the car.....maybe a year and two months. The old owner put some of that BLOCK SEALER in there, i might have to drain the cooling system and see if maybe there is something plugged up, gonna check the thermostat and see if that is plugged up.

BTW, where is the thermostat on this car?
 

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94 ETC,97 STS
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3,531 Posts
afterburn; said:
No headgasket problem, thats for sure.
Why do you state this?????????

Have you done exhaust byproduct or cyl pressure test?

edit to add:

And PLEASE.......don't say there is no coolant in the oil!
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
No headgasket problem, thats for sure.
No leaks or signs of leaks.
Belt is tight but not too tight.
Water pump is running nicely.

Cooland in other hand is bad, been in there for as long as i had the car.....maybe a year and two months. The old owner put some of that BLOCK SEALER in there, i might have to drain the cooling system and see if maybe there is something plugged up, gonna check the thermostat and see if that is plugged up.

BTW, where is the thermostat on this car?
I agree. How do you know for sure?

Yeah, definitely change the coolant, but you might want to get that byproducts test done first. The thermostat is located where the lower radiator hose hooks up to the waterpump housing. Two 10mm bolts need to be removed to take off the spigot and remove the thermostat.
 
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