Heater temp swings

Hi all -

I have an 92 LeSabre, 3.8, with only 25K original miles... Gramma never went anywhere but the store, bank, and gas station with it. I've found that ALOT of the replacements over the past year are due to the car NOT being used enough... I say with confidence that you will all agree!!!

Nonetheless, I ended up changing out the stat over the summer due to it finally failing. I ended up flushing the entire system out (Yes, completely), refilled with a 50/50, ran it for a good hour, drove it, all with success - until 2 days ago when the temp dropped to the single digits...

Now mind you - I know this car has always ran on the cool side; however, when my gauge is in the center, then quickly drops to the cool side, plateau's, then moves quickly towards the hot, then the heat cranks out like it should, it tells me that I have an issue. This happens at both stand-stills and while driving. At idle, you get 'nominal' heat and goofy temps. If you hit the gas, you'll see it change quickly as well (idle and/or driving).

My first guess was the water pump, given the behaviour and knowing that the thing is full & I changed the stat in the summer. Pump is great and stat is doing it's job as I can feel it opening & closing via the upper hose... So I think it could be a bad mix now, so I drain and refill using more antifreeze this time around - just speculating that I could have more water than antifreeze and these temp's require a different ratio.... Still no change....

I suppose my question(s) are 1) What is the proper mixture for this car in this environment (I'm in MI)? I'm a mechanical engineer by trade, but not in the auto field, so I'm sort of at a loss here. I mean common sense as well as the directions on the antifreeze bottle suffice, but heck - 2) If all is what is should be, is it more/less safe to assume that the frigid temps are affecting the engine temp? As I said above, you can tell physically and via the gauges when the stat opens - and it cools the thing right down to the "C" at times... The total loss of heat at any 'gauged' temp leads me to veer towards the pump still, but again, that's in good shape and is properly circulating accourding to the two outsiders who cannot 'find anything wrong'....

Thanks to all in advance who assist in this matter. I hoep you all have a great holiday as well; wish me luck so I don't freeze on my trip to Indiana in a few days :):)

You may want to check if your cooling fan is running all the time. On my 90 Lesaber, I found that the low speed circuit (for AC requests and controlled by the ECM) is constantly on.

Thanks for the suggestion Yogi - neither of the fans are running unless the car sits idle (running of course) for QUITE sometime. If they do come on, they run for maybe 60-90 seconds tops and then quit. They come on when the temp is a bit over the half-way mark on the gauge and subsequently quit once it lowers some. Now should I decide to rev the engine while under the hood (to ensure fans are on or off), you will see the temp drop drastically as mentioned in the original posting. If you rev it up while the fans are running, they will shut off quicker and the needle will drop....

Heck Im about ready to just put a piece of cardboard in front of the radiator and see if that has any effect on it!! LOL

Thanks again,
Niko

I'm Not sure but I think you can install the thermostat upside down on your engine. Did you make sure the pellet on the thermostat was pointing toward the engine and not the thermostat housing?

Initially it sounded like a stuck thermostat (even though it has been replaced you could have stirred up some chunks when flushing that get in the way) or a bad water pump impeller. But, have you looked at both of the heater hoses and radiator hoses to make sure that they are not collapsing?
You shouldn't have to worry about the mix causing a heat problem. All of the system water moves around when the engine is running and would mix/dilute everywhere but the overflow reservoir quickly.

Hope this has helped.

Thanks Wallus & sallison - I ceratinly apprecite the time you took to address this and help me :)

I'll address this (at least try - LOL) as a whole.....

#1 - Yes on stat install being correct.... Trust me - learned my lesson the hard way when I was still in High School... BIG nightmare, but this time around, no overheating - just the occasional 'veering' past the middle... No where near the hot ever....

#2 - The sediment build-up sounds like a GREAT plan of attack... Given that the car (really) never got 'used', chances are you have a valid point and great suggestion for me to try.... Makes sense - you can't exactly "flush" the thing entirely unless you do it over & over & over; but I'm assuming it will never be fully 'flushed'.. :):)

#3 - Accourding to 2 shops & a mechanic friend, that pump is not the culprit... However, I am not convinced of such - common sense dictates that SOMETHING is causing a blockage - either temporary as, e.g., the 'gunk' moves around, it blocks another hose, affects the impeller, etc. It's logical as if this 'chunk' gets stuck in the impeller, obviously flow will be restricted. Then, by revving the thing, it subsequently releases that 'chunk' and i've got flow again until the next stoppage... This may sound absurd, but is there a way to check the impeller w/out having to remove the SOB? Doesn't sound like it's an easy thing - especially in that packed area!!! :):)

#4 - Going along the lines of sallision's bad hoses, I just went and checked those for any type of collapsing, bulges, leaks, etc. on all affected areas. Checked both U & L hoses as well as both core hoses.... My opinion - they are dryrotting (if not already) and DO need to be replaced. Somewhere along the line, i heard that it is good practice to change the Upper hose if you change out the stat - or whenever you remove a hose. That leaves three left and again, I would replace them just for peace of mind at this point, pending it sounds like I need to re-flush the whole thing again anyway (LOLOL)...

#5 - Mixture - Well, if the chucks hold true, and since I'm changing hoses anyway when I drain and flush again, guess I'll do the 50/50 as I always have on all my vehicles... Thanks for letting me know that this is not something I should be worried about; regardless, due to #'s 2 & 3 above, i'm flushing again.... Gotta love this stuff eh?? :):):)

Well, Thanks again to both of you for your suggestions..... Give me about an hour 1/2 and I'll give you an update :):):) Niko

Hey Niko,
Sounds like you have a pretty good handle on the problem.

Yes, you can check the water pump impeller without removing it, at least you used to be able to by removing the LOWER radiator hose from the pump and sticking a heavy wire (thick coat hanget) up the lower outlet and hooking the impeller. Remove the drive belt and turn the pulley to see if the impeller slips. All this works if you can actually get to the outlet (which used to be easy on the older cars).

Generally a 50/50 mix gets you down to roughly -20 protection depending on your radiator capacity. The main reason for using anti-freeze is that it resists boiling up to around 235-240 under 15psi.

Check to make sure your cap seals correctly also.

Good Luck,
Steve

Better check the intake manifold could be leaking.this will make the temp swing.