1994 STS First Roadtrip Coolant Temp
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Northstar Engines and System Technical Discussion Discussion, 1994 STS First Roadtrip Coolant Temp in Cadillac Engine Technical Discussion; Hello, Just returned from a great roadtrip in the STS. What a fabulous touring car. My problem was apparently the ...
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    chevyorange's Avatar
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    Question 1994 STS First Roadtrip Coolant Temp

    Hello,

    Just returned from a great roadtrip in the STS. What a fabulous touring car.

    My problem was apparently the passing I did as we were driving through rural Eastern Washington. Outside temps were about 41-45F.

    I got a couple of "Coolant Hot" messages flick on and as I coasted down from 95MPH the message would go away and I watched the temp drop quickly from 240 to 195-200. It would only seem to get realy hot under two or three conseuctive full throttle blasts (imagine passing a car).

    I checked the coolant and it is fine (just had it flushed and filled), and I assume the water pump is fine, otherwise I don't think it would have cooled down as fast as it did (in seconds) or at all.

    My suspicion lies with the thermostat. The car is all original at 89K miles and wonder if anyone can think of anything else before I replace it. And also if you have any tips on replacing.

    Thanks for reading, happy motoring.

    Adam

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    dkozloski's Avatar
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    Re: 1994 STS First Roadtrip Coolant Temp

    I heard years ago that GM designed their cars to operate at 100MPH with a 100MPH following wind without over heating. I can't imagine any car that is supposed to heat up at the temps you describe.

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    Re: 1994 STS First Roadtrip Coolant Temp

    I should note that I was able to cruise at 95MPH for the majority of the trip with one burst up to 140 with no effects, it only seemed to happen under the two or three consecutive WOT when passing. And as noted, thankfully, it cooled down to normal so quickly it was just as odd to see it drop in temperature so quickly as much as it was a surprise to see it get that hot to begin with. I've NEVER had a GM car overheat on me.

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    Re: 1994 STS First Roadtrip Coolant Temp

    You're on the right track. Change the thermostat, [ very easy to do ] but only put in the genuine GM item!!
    My 94 Eldo temps dropped a honest 10-15 degrees and were more stable after installing the GM part.I found a non GM item installed. Also don't forget to put in the Barsleak Golden Seal additive. Do a search on the forum as there is a lot of information on this topic.
    Marshall

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    Re: 1994 STS First Roadtrip Coolant Temp

    Marshall,

    Thanks for the tip. I'll take a look at the Thermostat this week. I'll have to order (I wonder if my local Chevrolet dealership will have one - the Caddy dealership is far away).

    I did use the Barsleak when I flushed the system about 2 months ago!

    Adam

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    Re: 1994 STS First Roadtrip Coolant Temp

    Adam,

    I order from P&G [GM dealer] in PA. 1-888-870-0280 ext. 214.
    They seem to have the best prices or as good as any.
    Good Luck
    Marshall

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    Re: 1994 STS First Roadtrip Coolant Temp

    I'll give 'em a call! Thanks.

    Adam

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    Re: 1994 STS First Roadtrip Coolant Temp

    On a 94 I would DEFINITELY check the water pump drive belt and the water pump drive belt tensioner to make sure it is free to move and not corroded and stuck. Exercise the tensioner and lube the pivot point of the tensioner. Replace the water pump drive belt as, after 11 years, it doesn't owe you a dime and may be slipping. Many times, after 11 years, the tensioner on the water pump drive belt can get awfully stiff and not tension the belt properly so that it slips at high RPM and doesn't turn the water pump... The fact that it cools down immediately upon reducing RPM seems to point to something like that. The water pump is driven off the rear of the intake cam on the rear of the engine. Look directly behind the radiator in the middle of the car....

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    Re: 1994 STS First Roadtrip Coolant Temp

    bbob, I'm honored to have you respond to my problem!

    What do you recommend for lube on the tensioner? I'll do this over the weekend. Can't wait to not be afraid for 'higher speed' cruising in the right areas of the state.

    Adam

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    Re: 1994 STS First Roadtrip Coolant Temp

    Most any kind of grease or heavy oil. The little spring loaded tensioner for the water pump drive belt pivots on a post of sorts so you just want to lube it....some kind of spray grease in a solvent that makes it easy to apply is ideal...like the spray lithium grease in a rattle can that is in most automotive stores. It will penetrate and then the solvent flashes off leaving the grease in the joint hopefully.

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    Re: 1994 STS First Roadtrip Coolant Temp

    Regarding lithium grease - somewhat off-topic but potentially relevant question here:

    Does lithium grease stiffen substantially in cold teperatures? I put a quick spray of lithium grease on the hinges of my aluminum mailbox last summer, and on very cold days here (single digits above zero), the door is difficult to open. It doesn't just crack and then open fine, as if it were being held by ice, it's more like the hinge is very stiff, as if the lithium grease I sprayed in there is thick like molasses in January. I quit using lithium for applications that could be exposed to cold weather just in case, and I use a drop of light oil or SAE 30 instead.

    dkozloski, any thoughts here? I consider you the forum cold weather expert... :-)
    Mike

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    Re: 1994 STS First Roadtrip Coolant Temp

    For cold weather applications synthetics are the lubes of choice. For a heavy oil you might want to try Mobil1 gear oil. Don't get any on you 'cause it stinks. Most of the well known companies like Shell and Chevron make a whole line of synthetic products. I use a lot of silicon spray in place of the normal penetrating lubes like WD-40 or CRC 5-56 in cold weather. Keep the can under your coat or you won't get anything out of it. On a day like today, -35F, you'd have a tough time driving a nail into lithium or sodium base greases.

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    Re: 1994 STS First Roadtrip Coolant Temp

    Quote Originally Posted by dkozloski

    On a day like today, -35F, you'd have a tough time driving a nail into lithium or sodium base greases.

    LOL LOL LOL LOL MInd if I use that line...??? Perfect description.

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    Lightbulb Re: 1994 STS First Roadtrip Coolant Temp

    Excellent info, dkozloski, thanks! So, with that in mind, if the component to be lubricated could be exposed to cold temperatures (positive single digits and below in my opinion), you might want to avoid the lithium grease because it does harden. When I lube my own water pump belt tensioner, I will use either some cheapie SAE30 oil or, if it's going to be really cold, like, say, in Fairbanks, Alaska, I'd use a few drops of some kind of synthetic product. Sound reasonable to everyone?

    By the way, dkozloski, don't you usually start your spring cleaning when the temp gets above about -40F? To compare and contrast a little, another friend of mine in Marathon, FL is enjoying daily low temperatures approximately 100 degrees higher than in Fairbanks... Ahhh, pish-posh. What's 100 degrees, right?
    Mike

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    Re: 1994 STS First Roadtrip Coolant Temp

    Quote Originally Posted by bbob
    On a 94 I would DEFINITELY check the water pump drive belt and the water pump drive belt tensioner to make sure it is free to move and not corroded and stuck. Exercise the tensioner and lube the pivot point of the tensioner. Replace the water pump drive belt as, after 11 years, it doesn't owe you a dime and may be slipping. Many times, after 11 years, the tensioner on the water pump drive belt can get awfully stiff and not tension the belt properly so that it slips at high RPM and doesn't turn the water pump... The fact that it cools down immediately upon reducing RPM seems to point to something like that. The water pump is driven off the rear of the intake cam on the rear of the engine. Look directly behind the radiator in the middle of the car....
    Well, I'm not sure if I have good news to report. Belt, pullies and tensioner are all very good, clean and work. What I have noticed is that water/coolant tends to go "missing" out of my overflow tank. I had to add nearly a gallon last week when checking this problem. I had the whole thing flushed/filled/tabs put in at my local mechanic who is very good.

    I'm not sure if they didn't fill all the way (on accident of course) or if coolant is "burning"? I can see me exhaust most all the time but it isn't oil, and the temps have been pretty cold around here since I've bought the car (40s and 30s).

    The car runs great, strong starts good and no liquid out of the exhaust.

    Is this the beginning or the after effects of a head problem?

    Adam
    94STS 90,047 miles

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