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I have a 94 Seville SLS, it overheats every time I step into it to pass a car The temp goes up to 256 then says engine hot. it pushes the coolant out the radiator cap overflow tube. there is no smoke from the exhaust nor is there any sign of water in the oil. I have replaced the radiator, waterpump and thermostat there are no leaks anywhere.
Anyone got any Ideas ????????
 

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rag71359 said:
Anyone got any Ideas ????????
Radiator fan(s) aren't working.

Theromstat isn't working. (Can check that in a pan of water with a meat thermometer on your stove by suspending theromstat in the water as you boil it.)

Waterpump impeller stuck. (doubtful)

Take it to a reputable radiator shop and see what they say. I'm sure they've seen this problem 1000 times before it they've been around a long time.

..rickko..
 

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Id go ahead and replace the Tstat and give it a good cooling system flush..... it'll only cost you about 15... make it an afternoon thing......

Let the car idle for a while and see if the fans come on....... i dont recall if there's any way to test the fans..... Im sure there is, but I dont know it....
 

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I think the fans on the Northstar are set to come on at 230 degrees. They should also come on automatically with the a/c. If they dont come on, start by checking the fuse. After that, you might check and replace the 3 relays and check that everything on the relay is connected right. The 10 amp control circuit was somehow not connected on mine. If all else fails, try rplacing the drivers side fan motor. About $30 from O'Reilly's Auto Parts.
 

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Discussion Starter #5
Loud 93 STS said:
I think the fans on the Northstar are set to come on at 230 degrees. They should also come on automatically with the a/c. If they dont come on, start by checking the fuse. After that, you might check and replace the 3 relays and check that everything on the relay is connected right. The 10 amp control circuit was somehow not connected on mine. If all else fails, try rplacing the drivers side fan motor. About $30 from O'Reilly's Auto Parts.

My Fans do come on. I replaced the thermostat and still the same problem. it seems to be getting worse, now evan when i drive very easy on the gas it loses allthe coolant. It seems to build a lot of pressure then pushes the coolant out the overfill tube. someone told me that there is a bypass tube that goes between the heads that could be plugged. or that a head gasket could be blown and pushing pressure into the cooling system. I have no idea. !!!
 

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Is the radiator origional...? If so, its probably really gummed up with calcium.... Especially if the coolant hasnt been changed really often....

Sometimes you can get radiators cleaned (aka cored) at radiator shops, and its usually about 100 for the procedure........ Not sure if your radiator can do it, but it'd be worth a shot......
 

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Cooling fans would not likely be the culprit if it overheats while passing at speed (I see you posted that they are working). There is usually enough air pushing through the rad at highway speeds to provide adequate cooling.

To me it sounds like a headgasket blown between the combustion chamber and water jacket. Combustion pressure is much higher than the pressure the rad cap releases at. When you tap into the power & more air-fuel mixture is drawn into the cylinder, the combustion pressure gets higher. The pressure pushes down on the piston, but also lifts on the head. It may seal fine at idle (low combustion pressure), but leak under load.

Have a shop do a sniffer test at the neck of the coolant reservoir. If the tech finds carbon monoxide or hydrocarbons in the coolant, it means combustion products are getting into the water jacket. At best it's a blown headgasket. Worse could be a cracked head or block.

There are a bunch of threads here on headgaskets. Do a search of the site & do some reading. This isn't a job for the average Joe, but you'll be less likely to crack your head on the garage floor when you get an estimate.

Good luck.
 

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Might as well replace it.... Its only a few dollars at your nearest auto parts store......
 

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Discussion Starter #10
elwesso said:
Might as well replace it.... Its only a few dollars at your nearest auto parts store......

Already replaced the cap. but thanks .still don't know where to go with it yet.what ever it is it seems to be getting worse , I can't evan drive it taking it easy now it pushes the water out at low speeds now.
 

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Check the Gasket and gasket surface in the filler neck. I have seen new caps with gaskets that are incorrect for the filler neck.
 

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I agree with eehoe on this one Rag,sounds like you have combustion pressure going into the cooling system via headgasket blown or cracks in the head,it is the only thing that makes sense about the higher revs and it is getting worse as time goes along ,hole or crack getting bigger.The sniffer should tell you if this is the prob,keep us posted.
 

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Take a look in the N* performance and tech section. The thread is coolant loss. I told him how to do a compression test. If your technical enough that should be your next step. It should take about an hour, maybe more if you're learning.

This will determine a lot. If you don't want to do the compression test have a shop do the sniffer on the cooling system.At least you'll know if it's head gaskets or not and you won't waste any more time on other things unnecessarilly.

If you look at the pics on this link you'll see the coolant passages totally surround the cylinders. This is why you don't see water in the oil until the gasket is really blown. The oil drain passages are the three oval ones at the bottom of the deck.
 

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Discussion Starter #15
zonie77 said:
Oops, forgot the link..........

http://caddyinfo.netgetgoing.com/howto/nsrepair.htm

P.S. he says the repair was a waste of time but we found 6 holes with badddd threads.
I found the return hose nipple that comes out of the top radiator hose housing, was plugged with a gob of silicone. Ialso replaced the four water corse gaskets.The problem of blowing the coolant out the overflow tube has stopped. How ever every time I drive the car I still lose about a quart of coolant. where it goes I don't know but it is dry as a bone under the car and nothing in the oil and no smoke either.
Someone told me that there is a high speed radiator relay that these cars have and are known to go bad, which could cause this problem.
anyone heard of this ??????
 

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Please clarify which 4 gaskets you replaced. I'm not sure which ones you mean.

Head gasket problems are pretty common in overheating N*. Get the combustion leakage test or a compression test done to eliminate that possibility.

N* with bad head gaskets usually don't get water in the oil.

I'm glad you were able to fix a lot of it easily.
 

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Discussion Starter #17
zonie77 said:
Please clarify which 4 gaskets you replaced. I'm not sure which ones you mean.

Head gasket problems are pretty common in overheating N*. Get the combustion leakage test or a compression test done to eliminate that possibility.

N* with bad head gaskets usually don't get water in the oil.

I'm glad you were able to fix a lot of it easily.
The waterpump housing has four gaskets where it connects to the heads and block on the back of the engine.
Have you ever herd of a high speed radiator relay ??
 

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Discussion Starter #18
elwesso said:
Is the radiator origional...? If so, its probably really gummed up with calcium.... Especially if the coolant hasnt been changed really often....

Sometimes you can get radiators cleaned (aka cored) at radiator shops, and its usually about 100 for the procedure........ Not sure if your radiator can do it, but it'd be worth a shot......

I found the return hose nipple that comes out of the top radiator hose housing, was plugged with a gob of silicone. Ialso replaced the four water corse gaskets.The problem of blowing the coolant out the overflow tube has stopped. How ever every time I drive the car I still lose about a quart of coolant. where it goes I don't know but it is dry as a bone under the car and nothing in the oil and no smoke either.
Someone told me that there is a high speed radiator relay that these cars have and are known to go bad, which could cause this problem.
anyone heard of this ??????
 
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