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Hello, I am on an errand for my father as he is not what you'd call "computer literate" hehe. Well, he's the owner of a 98 Cadillac Seville SLS with over 100k milage (not sure of the approximate), and he recently replaced the radiator over the summer and now it's experiencing some majoy overheating. The car will get to very high temperatures from a mere drive 'around the block'. My father is thinking there's a warped or blown head gasket, but I feel that seems unlikely. The car is without a thermostat as well, would this contribute to readings of overheating at all? We also suspect someting may have gone awry with the water pump, but the evidence is a bit inconclusive at this point. I read all about the subject on the forums here before posting this and saw such things as coolant problems, fan problems ect, but according to my father, these things are all running well, though he doesn't know if there is significant combustion in the coolant or leaking of water/fluids into other parts of the engine. If it is the head gasket, are they particularly easy to replace, and where could I find a guide for doing so, as taking it to a shop seems extremely expensive. Thanks for reading, I look foward to your responses.
 

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If you search for head gaskets, they are a massive pain to replace, but not impossible. Usually you'll see a lot of white pale smoke from the exhaust (sometimes you wont, and a pressure test is needed).

Is the car losing any coolant? Was the air properly bled from the cooling system after the radiator was installed?
 

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1989 Sedan DeVille is now just a fond memory ....
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As Jesda said, keep an eye on the coolant level. You need to replace the thermostat. It will run cooler with one than without. From your description it does sound like there is more of a problem and proper diagnoisis is imperative.

Again as Jesda had posted, there is a plethera of information in this site, most of which can be found using the search tool. If you need any help with that please ask.
 

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For info on how to change head gaskets look in the tech tips section.

No thermostat is not going to cause an overheating problem in short trips. Most things that cause overheating won't show up in a couple of miles.

Verify the water pump drive belt is good and the tensioner working. If it's losing coolant there's a good chance it's the head gaskets. A cyl pressure test will confirm. Heating up that quickly is not a good sign.
 

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Also check the purge line to be sure it is clear and flowing. No need to bleed air from the system. It is self purging, assuming the purge line is clear. If not, it will overheat.
 

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Hmm... Are there any codes? I know this might be a stupid question but, did he plug the fans in after the radiator installation? Are the fans turning on at the right temp.? Try turning off the a/c and see if the fans turn on at all when it gets up to temp. Are you loosing coolant?
 

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Buried_Inside said:
The car will get to very high temperatures from a mere drive 'around the block'.
The laws of thermodynamics would indicate that it's air and not fluid that's heating up then - if the coolant is flowing through the system as it should and the system has been purged of air then a rapid temp increase like that is unlikely.

Out of curiosity - have any of you tried Red Lines "water wetter" in your caddy engines? I used to run it in an SCCA VW Scirocco 16V GTI that I raced (they tend to run hot) - it serves to decrease coolant temperature by as much as 30 degrees. I'm going to try it in my Seville - it works with anti-freeze compounds - I'll post my results.

The link to water wetter is http://www.redlineoil.com/products_coolant.asp
if you're interested.

All the best

Steve
 

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As you know I have problems of my own in being discussed in the Bars Leak Post.

To me, it would seem if air was in your system then taking the Radiator Cap off, and letting engine run hot for a few minutes would relieve all the air. The small 3/8 inch hose going from top of my overflow tank to under the intake manifold on my 94sts is supposedly carrying the air out of the cooling system and into overflow / pressure tank. But if Radiator Cap is on, the air cannot escape, so I assume.

Anyway, just a thought I have.

Thanks for your advice, hope mine helps you.
 

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.... I remember the "good old days" when purging a cooling system of air was a simple matter ...... maybe I can find a '67 Caddy to replace my '92 with. As I recall, diagnostics for ignition and fuel system problems were a heck of a lot easier as well.
Could it be that vehicles have become so sophisticated in the past couple of decades that, from a home mechanics point of view, we're reaching a point where we will no longer be able to work on our own cars?
I'll admit that I don't miss setting point gaps or dwell, nor do I miss rebuilding carbs, but in the same breath I have to admit that I miss knowing that, if the situation arose where I needed to do work on the fuel or ignition system, that I could accomplish my tasks without the need for a computer diagnostic system, special tools or the rest of the "stuff" we're forced to use now ...

Just waxing nostalgic I suppose ....

Steve
 

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rfishing said:
As you know I have problems of my own in being discussed in the Bars Leak Post.

To me, it would seem if air was in your system then taking the Radiator Cap off, and letting engine run hot for a few minutes would relieve all the air. The small 3/8 inch hose going from top of my overflow tank to under the intake manifold on my 94sts is supposedly carrying the air out of the cooling system and into overflow / pressure tank. But if Radiator Cap is on, the air cannot escape, so I assume.

Anyway, just a thought I have.

Thanks for your advice, hope mine helps you.
The air will expand more than the fluid will, and the system pressure will quickly exceed 15 PSI. The surge tank pressure cap will vent the air quickly. No need to remove the cap. On the flip side, when the pressure drops again and the air and fluid contract, the pressure cap will let air in to equalize the pressure. The vapor vent line purges the air out of the water pump cavity and thereby removes most of the air from the system, leaving it in the pressure tank where it is vented appropriately by the cap. A properly functioning cap is critical to correct system performance, but is an often overlooked source of problems. A new cap is a $5 item, and it could help save a $3000 head gasket repair job and a lot of frustration. 15 PSI is the cap pressure rating on my '96 SLS, and I assume all other 4.6L Northstar V-8s.
 

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deskjockey said:
I have this same problem, how do you purge the air?
The 4.6L Northstar V-8 cooling system is self-purging as long as the vapor vent line is not clogged. There is nothing to do to burp or purge the system. You don't have to remove the cap to vent anything. The vapor vent hose extends from the water pump housing to the coolant surge tank.

If gases are continually being pushed into the cooling system, it could be from a leaking head gasket. If that's the case, a test will show hydrocarbons in the cooling system, but a cylinder pressurization test will show definitively if the head gaskets are leaking into the cooling system. The only solution for leaking head gaskets is to replace them. Anything else is temporary at best.
 

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SteveThefolkie said:
....
Could it be that vehicles have become so sophisticated in the past couple of decades that, from a home mechanics point of view, we're reaching a point where we will no longer be able to work on our own cars?
I'll admit that I don't miss setting point gaps or dwell, nor do I miss rebuilding carbs, but in the same breath I have to admit that I miss knowing that, if the situation arose where I needed to do work on the fuel or ignition system, that I could accomplish my tasks without the need for a computer diagnostic system, special tools or the rest of the "stuff" we're forced to use now ...

Steve

The new systems aren't that hard to work on but you are forced to learn what you are doing. I remember many guys that messed up their cars because they didn't do the work right. They were able to keep them running but not running well. That's the only real difference. Now you have to fix it right.
 

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Discussion Starter #14
Thank you all for the responses. We seem to have found the problem. The box that's connected to the radiator through a hose (resevior I believe it's called) was completey clogged. We've since removed it and thoroughly cleaned it out. It seems it hasnt been cleaned since the car was first made. Massive relief to know it wasn't the head gasket, to be sure.
 

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Someone may have put the cooling system suppliment (sealnt tabs) in the surge tank. That is exactly why it is recommended to put them in the radiator hose. Glad you got the problem fixed cheaply and easily.
 

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That does not sound logical. Coolant is continiously flowing through the heater core. The only thing that happens when you request heat is that an air mix door opens to allow warm air into the cabin. Maybe just a coincidence. Have you verified that the purge line is clear and flowing? Have you put a 1/4" breaker bar on the water pump tensioner and excercised it to be sure it is not rusted in place and is providing enough tension to prevent the belt from slipping?
 

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My 99 STS overheated the other day and we've been hearing a sloshing sound inside the car for months. I recently took it to have the coolant flushed so when it overheated afterwards and we still could hear the sloshing sound I took it back to have it checked again. The mechanic (or technician as they are now called) said it looked like a head gasket (which they will not replace, preferring to leave that up to a dealer) because he did a hydrocarbon and CO2 test in the recovery tank and found both. It would not overheat for him, the system pressure tested out good the fans came on, and the cap was good. If I remember correctly he said the CO2 spiked in the tank at about 200 degrees. He explained that it could be the head gasket, or a head bolt that has come loose or broken from corrosion resulting from coolant attacking the metal.

I can't afford to have the head gaskets replaced in it so I'm forced to at least do as much of the work as I can.

I read about doing the leakdown test in this forum and I'm preparing to do that, but I find it interesting that the purge line between the water pump and the recovery tank could be plugged and cause both the sound and the overheating, right? The car only has 54K on it and runs perfectly otherwise and the only reason we took it to have it flushed is because of the sound we heard and we were told the systems had to be purged.

PS Haven't noticed any unusual smoke out of the tailpipes.
 

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The hydrocarbons in the coolant are not a good sign, but check the purge line first. It can cause the symptoms you are experiencing.
 
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