94 sls problem overheats please help

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94sls

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I just bought a 94 sls northstar, after i drove it home about a 20 mile trip i notice steam from the coolant surge tank, I then noticed one of my fan's did not work so i replaced it but the coolant temp raised above 250, i then noticed the rad had a crack in it so i replaced it and decided to replace the water pump and thermostat. Now even with all that changed i still over heat, I've read in the mitchell on demand progam to add 3 collant pellets and it gives a part number,
can anyone of you guys please tell me what are these pellets and what problem do u think i have .,..,,
 
First thing I'd do is buy, rent or borrow a pressure tester and test the system.If it holds pressure, fill it up and run the engine with the cap off the radiator until it starts to overflow, that'll let any air out and if it starts to overflow, then you know the pump and thermostat is working right.If it has a leak, when you apply pressure, it'll be obvious where the leak is.BTW, just because you don't see fluid on the ground, doesn't mean that the system isn't leaking.If it is leaking, it can get an air pocket somewhere and stop the coolant flow.I don't know what the pellets are, but I doubt they have anything to do with how the system works.
 
I thought maybe I'd add something to this. When you were having problems, did the car get really hot? Getting an engine with aluminum heads hot even once can be very detrimental to the engine.I just cracked a head yesterday, because it got too hot, and I thought I could make it home. When you changed the radiator and the pump, did you replace the hose clamps?You say that the car is overheating, but are you sure that the temp sensor is reading correctly, in other words, are you sure that the car is overheating, or is the dash telling you that it is. You've replaced basically every component of the cooling system and it really should be ok.I guess what I'm saying is, everyone tries to help each other with this diagnostic s*** over the internet, but in order to properly diagnose the problem, we need alot of info.There are many things that can mess up a cooling system.From bad thermostats to freeze plugs leaking to who knows what.The more you can tell us, the more we can tell you.
 
Thank you, The Car is overheating the temp guage says 255,257 then its says coolant hot, then engine hot.but i heard that with the northstar, when the engine has no coolant after it over heats the engine puts it self in camel mode where it cuts off 4cylinders then turns them back on when their cool and cuts off the other 4 until you reach your destanation i have noticed that this must have happend becuase i was able to keep driven but i really did have any real engine power, I also noticed that when i start the car with the rad cap off the coolant bubbles out even when it's cold as if it where boiling, i believe i might have a head gasket problem. My mitchell on Demand Program must know this because the pellets with th GM part number that the recomend is acually a stop leak, so i really think GM knows this also that the might have had head gasket problems with this junky northstar. there is obvius coolant leak no oil water mixture put somehow there has to be a blown head gasket and i heard that it's very costly so i got screwd paid 1800 so i just want to sell it. it's a very clean very pretty car.
 
I didn't want to say it because I don't like to say this is wrong or that's wrong when theres no way to really tell over the internet,but head gasket is what came to mind.Check the exhaust coming out and see if it's white, or if it smells sweet.Basically, a head gasket can do 3 things, leak into an oil passage, leak out from under the head onto the ground, or leak into the cylinder and burn.That goes for oil and coolant.If you can't do the work yourself, it'll probably be pretty costly.I wish I had the money.I've been wanting a Caddy for a while, and the only way I'm going to get one is to buy a fixer-upper.The problem with buying cars with blown head gaskets, is if you run an engine with aluminum heads hot, theres a good chance that the head could be cracked or warped.All of a sudden, the total spent on the car could have bought one that wasn't broken.
 
Damn 94SLS

Theres no oil in the coolant not coolant in the oil, no visible leaks and no smoke the car runs really good it just over heats. and the wierd thing is i can drive for two or three hours somtimes and have no problems the temo stays around 203- 205 and then all of the sudden it goes up to 250 then 255 then boils over i cant see any of the typical head gasket problems and i dont see any steam out of the exhaust. Today i removed the thermostat and i added some block sealant called blue devil it cost around 70 dollars i let it run for 40 min like the directions said next i'm sopposed to put the thermostat back in i haven't done that yet but
the car hasn't over heated either i hope that it doesnt i spent a lot of time and money in this over the last two weeks. Thanks for your help

i'll let you know if the stuff works
 
you should try doing what crazyman said, leave the cap off and let it run untill it gets hot. Its allmost definately a vapor lock, i have a 94 Linc mark VIII and its done that to me. I put a new radiator in it, new water pump and thermostat and it came out to just being a vapor lock. Try that and see if it works. I also have a 98 STS that the head gasket got blown on it and i just bout a new factory motor from some guy i know that bought one and was going to use it but he decided not to. I paid 3,500 for it so imma just swap the motors and keep the other one to build it up and play with it for later usage.
 
You have/had a blown head gasket. Hot combustion gases were seeping into the water through the faulty gasket seal and was overheating the system. The bubbling is a typical sign. Your situation is not unique. It happens from time-to-time. I hope your sealant works. I used SolderSeal's Block Seal on a blown head gasket once and it worked fine.
 
94 sls

thanks i since i thought i bleed the system for like three days i didn't have any problem the car would heat up but it leaked water out of the surge tanks overflow valve a few times but the engine temp didnt rise above 225 but every so often it leak antifreeze the coolant was low. then the temp went to 250 but it would go up and down 250, 244, 239, then bakc to 250 then the heater core blew out. this is my first caddy and i've heard bad things about northstars i dont think i' would buy another.
 
Remember you have a 94, not a new Northstar. I'm sure you'll hear a bunch of criticisms about Northstar engines i.e., burn oil, leak oil, head gaskets blow, etc. However, don't get too frustrated. I own a 94 Eldorado with 177,000 and it runs like new. I assume your 94’ is close to 100,000 miles or over? With that kind of mileage things tend to happen. Hopefully, the overheating problem is solved and you’ll be trouble free from here on out.
 
I meant your Northstar is not brand new. Not that you didn't have a Northstar.
 
Hey 94SLS,
Did you ever find your overheat problem?
I had the same problem with my 94STS. Changed everything except the head gasket. That was my next move.Until i found out on another site that there is a hollow 3/8 bolt with a host connected to it right above the waterpump that can get clogged preventing ait from purging the system. I took the hose off and the bolt out, turns out it was clogged with pieces of the rubber hose that broke off from the inside and logged into the hollow bolt. Cleaned it out changed the hoses and never overheated again. Also check the line that runs from the surge tank, under the intake cover. It get's clogged also.
 
wow.wow.wow.wow.wow. hhhmmmm ok. call me young but my car did the same thing for over a month until i finally got the bleed right. These cooling systems are more stuborn than a little kid who just dropped his ice cream and then accidently sat in it!No joke. i would bleed the system by filling it,running it till it came up to normal temp,(with cap off),let it run for a few mins to pop out some air.And then my favorite, SHUTTING IT OFF.now when u shut it off coolant will come pouring out of the tank.bubbling and so on, probly bout a gallon or so.Fill it back up.LEave the cap off and come back every 2 or 3 mins and keep adding. the coolant should be settling in. bout 10 mins or so should be enough.cap it up!!! If desired, do it again. mine did the SAME STINKIN THING.it would be good for a day or so then start climbing.teasing me and pouring salt into my eyes!!!. anyways . i hope this works for you. ive been driving mine now for a month and no temp climbs yet.LET ME KNOW!!
 
also try to see if the clamp on the bottom driver-side radiator hose is firmly clamed and connected....its very big, u shouldnt miss it...its very hard to get to without a long-ass screwdriver.

mine kept doing the same thing and i would notice coolant on the air filter box. so i tightened every damn hose i could see... and finally found the clamp was loose from coolant every so slight on the bottom of the hose. Problem solved, no more CHECK COOLANT lights, with spilling over bs happening
 
More on problems with 94 Cadillac Seville SLS

My 94 SLS is doing the same things as you have been discussing. (Overheating) The car has only got 72,000 miles on it. In the last 2 months I have spent approximately $1500 trying to get the problem fixed. I took it to a Cadillac dealer to start with - they changed the ignition control module - after keeping the car for about 4-5 days. They also at 60,000 miles did the 10,000 mile tune up (dumb me I let them - they had themselves a sucker on the hook. Then I took it to a service station that has a really excellent reputation for providing great service. They changed the thermostat, the housing for the thermostat, a valve and a belt. I left the station and the car did the same thing. They took it back - kept it a few days and even gave me a loaner to use (without charge). This time they did the bleeding for air - I got the car back(at no charge) and 2 days later it was doing the same thing. This time they changed a sensor for the engine coolant (because previously we had determined that the car actually isn't overheating - sometimes it would only be 115 or 150 and it would come on saying it was overheated). We were all sure that the problem had finally been solved. I got the car back on Friday and didn't drive it much over the weekend. Monday morning on my way to work it did the same thing. The guy that owns the service shop promised we would get to the bottom of it and he was going to contact some technicians and see what they could come up with. That was last Wednesday and I haven't heard back from him since. I am worried - does anyone have any suggestions on where to proceed from here?
 
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