Coolant Temp Question

[farnelle]

Since my problem with the idle dropping off and the IAC cleaning procedure, I have been watching the gauge screen on my 89. Normally, I just run with the summary screen on.

The other day while waiting in line at Wendy's behind a person who must have been getting 10 orders, I noticed the engine temp rising until it got to 228 just as I pulled off. It cooled down once I got on the road. When I got home I checked the coolant resevior and needed to add about 1/2 gallon.

Since then I notice upon watching the screen that the temperature is constantly changing. For instance, while driving down the interstate this morning with outside temp being 29 degrees, the engine temp would rise to 192 then go back down to 179 then rise back up to 190 etc. I don't guess there is anything really wrong, but am interested in whether some of you guys with touchscreens have noticed the same thing. I really do not know how the engine temp can get cooler by ten degrees within 1 minute or two.

Another thing I have noticed is that neither fan pusher or puller seems to be working, but again, the temperature has been fairly cool lately. It may not be getting hot enough for the pusher fan to come on. I tried turning the air conditioning down all the way to get the puller fan to come on, but don't know if that will acutate the fan when the outside air temp is cold

Would be interesting in any information you guys might have. Maybe ...just go back to the summary screen and forget it unless I get a news flash on the screen telling me something is wrong.

[Guest wally888]

Perhaps the 1/2 gallon shortage influenced the 228* reading however my experience has been, even when OAT is near 100*, if fans are working properly, you should see about 213* then, as fans go to high speed, see a drop in coolant temp.

[padgett]

Shouldn't vary much when driving down road, mine usually runs between 179 and 181 on road with OAT below 90 (180 thermostat), that kind of excursion sounds like you are in the market for a new thermostat and might as well flush the system while at it.

When I first had mine I would see occasional excursions to 213ish and that is too high for me. After replacing the thermostat with a Stant "Superstat", flushing, and reprogramming the fans to kick in much earlier, mine sits as above in the cool months and when it gets hot it may hit 191-192 at a stoplight.

Good news is that since it does come back down when moving, the radiator and basic cooling system is probably OK.

[farnelle]

Padgett, I agree and was thinking thermostat also, but even with a bad stat, I can't fathom how it can vary 10 or more degrees in a minute or two. Wonder if it can be a bad sensor?

I am pretty squeemish? about temps in the 220+ range even though I recently read on this forum that General Motors does see have a problem until 230 or so. I wonder if anyone knows the temp that would have to be reached before there is a warning light or screen engaged? Thanks guys.

[Guest DTerry]

You mean it's unusual for the temp to change that quickly? Mine will change rapidly if I tromp on it or on a steep hill. 197 seems to be thermostat open temp (195 is design temp), and normally runs at 197, but will increase 10 - 15 degrees soon (like right now) under acceleration. Hot summer day idle, A/C, stopped, have seen over 120, but never overheated. Is this abnormal?

[Shelby]

I think you should be figuring out what happen to the Coolant.

[Barney Eaton]

For some reason I have seen several thermostats go bad. I am presently running a 190 with a lifetime warranty and it seems to be sticking (not opening until 10+ degrees past it's rating)

I was also needing to add coolant every couple of months, the problem finally showed itself with a puddle under the water pump. Changed that this weekend with a lifetime warranty aftermarket pump. After installing I turned the pump shaft to find there was a slight bind in about 30 degrees of rotation.

Pulled the pump and there were small scratches on the mating surface by the impeller. Dremel tool work on the impeller and back on.

[Guest wally888]

There are several articles re. this issue at site below.

Click on FAQ then go to "old" FAQ, then Cooling.

[padgett]

The General appears to believe that there is nothing wrong with 230F coolant temps, note how over the years there has been a steady climb of the center mark (is now 220F).

That said, I tend to keep things far past their sell-by date as evidenced by the fact that our "new" car is a '92.

We live in a hot climate and over the years I have found that just about everything (belts, hoses, batteries) lasts longer if kept cool so for our computer cars I aim for 180-190F operating temp and it pays off.

(Also decided around 1975 that a 3-4 liter six cyl was ideal for this country, evidently a few others agreed).

Yes, it takes a bit of work to achieve this, but the freedom from car payments makes it worthwhile.

[Guest]

My Temp was always running high. Always ran about 203 to 213 degrees. Switched to a 180 degree thermostat and now it's between 179 and 181. It's not an easy one to replace.

Tessann

[Guest]

For whatever it's worth, here's what my 88 does (I believe my coolant system is stock, with the factory spec thermostat, and the fans at the factory set points). For steady speeds above say 35 mph, the coolant temps will run from 90 to 110 degrees above the outside temperature - no surprises here. Even on the warmest days, I won't see the coolant temps get high enough for the thermostat to open. However, at idle, everything changes, and the temps will vary widely, especially on warm days. But, this seems to track with the set points on the cooling system (thermostat goes from closed to fully open 195 - 210, and low speed fan kicks in at 214). Never see it hit 220 - so I don't even know if the high speed fans kick in at 226. In fact, when the low speed fan kicks in, it usually drops quickly back below 200. FYI, I keep the gage screen displayed 95% of the time.

Having said all this, will probably go to a lower threshold thermostat in the spring (appreciate any suggestions on what type to buy). Also curious - it was mentioned above that the set points on the fans can be adjusted. Where would I find out how to do that?

Of interest, my 2003 Corvette will run at 192 degrees at a steady speed, irregardless of the outside temperature, but when idling in hot weather, I've seen it get up to 223. As mentioned earlier, GM seems to be comfortable with these high temperatures. I'm using MOBIL 1 5W-30 in the Reatta, which I believe is well suited to these occasional temperature spikes.

[padgett]

To adjust the fan points you change four bytes in the PROM. Easy with about $200 worth of equipment (have said what in previous posts).

The general is comfortable with high temperatures, he is only worried about 5/50. For those of us who tend to run way past there, I like to run a bit cooler, engine may not care but everything else in the engine compartment does.