I have a 1999 sls. bought it 2.5 years ago. Had 27000 original miles. Ran great for a long time until I had a new water pump w/thermostat put in. It ran well for awhile then it started to slowly creep to the over heating section one day the "red zone". I use Dex-cool, and synthetic oil. This past weekend I took it back to my mech. and we thought maybe it was an air bubble but it was'nt so artie put in some more of the silicate pellets and idled it for awhile and then parked it for a day and a half telling me that this way the silicate can set up in what leaks the engine may have. I asked him was this normal procedure or is he just putting on a band-aid where a band-aid will not work. We use the Dex-cool, but when I picked up my car yesterday, within 18 miles it went into the red zone and then back slowly to normal. Can you please apprise me of what else it could be, or what I can try? Please don't tell me it's the Head-Gasket. Respectfully,Dwight Clark
Country: United StatesMake: CadillacModel: Seville SLSYear: 1999Engine: 4.5
Flushing system, new water pump, and thermostat. Filled with Dex-cool, added silicate pellets. Car has only 58000 original miles on it and does not get abused
Welcome to JustAnswer, my name is XXXXX XXXXX X'm here to help get your problem resolved. Does it overheat at all speeds or only low speeds? Is it going through any coolant? Thanks
It starts to overheat at slower speeds, and then if I am at a stand still I will put it into neutral and give it a little gas, tach it to about 2000 on the tach and gauge needle will return to normal. The coolant level basically holds its content until it overheats and then buy releasing pressure through resovoir tank it might drop a little
Does the heat stop working when it starts getting hot? How long did it run well for after pump was replaced? I'd assume pump and thermostat were replaced because it was starting to run hot to begin with? Thanks
No, that was one way I was using to expel the heat in enging to try and return needle to normal range. Before new waterpump and thermo. was put in it never ran hot until the summer before last concerning the air cond. The mech. said it might have something to do with thermo. Then he told me it was waterpump. As far as it ever hitting "red zone" that did not happen until 3 weeks ago. I read the Cad. Manual and did the shut down, putting it in neutral and the likes, but for some reason it didn't work what he did. He had an employee of his that did not look as though he wasn't into his work put the new water-pump in, is there such a thing as putting the water-pump in wrong Dan, or does it fit just one way. I keep getting this remark from my mech. that the NorthStar system is not worth it's rep. Is this true? Remember this engine only has 58000 original on it. Please respond, Dwight
These engines are VERY common for headgaskets to leak by pushing exhaust gas into coolant which causes air bubbles and makes coolant not circulate but that usually stops heat from working. To be 100% sure headgasket is good you would want to do a cooling system pressure test to verify pressure doesnt drop and also a block test which checks for exhaust gas in coolant meaning headgasket is leaking. If both are good then the next step is to have cooling system bled good to make sure no air is in system. If good, then make sure cooling fans are working at high speed, this will cause it to overheat at lower speeds. If cooling fans are working, headgaskets test good, then it sounds like the radiator may be partially clogged which would also explain why it overheats only at lower speeds but heat still works good. The fact heat works is a good sign that its not headgasket problems but your mechanic is right, these engines are designed to fail pretty much. Let me know if you have any questions at all, Thanks Dwight.
Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
Dan about how much would it be to have engine replaced in this cad?
It is about a 20 hour job and you can find a engine for around 3k, so around 5k total depending on where you go. Make sure pressure test and block test is done before assuming headgaskets are bad. Let me know if you have any questions at all and let me know what outcome is. Thanks.
O>K Dan I thank you kindly for your time and expertise. I truly hope U have a great 4th. Just one more question what is the sign to look out for if I drive my cad. and the headgasket goes "God forbid", will I start losing power and that is the sign or is there something else?
The headgaskets usually do not give out completely where it will cause vehicle to break down, it will just overheat. But if engine starts to get too hot you need to shut it off and let it cool down. Running until it continues to get in high zone will cause major engine damage. Thanks again and happy 4th.