Running Hot

Gets warm in San Diego, but my 90 has never run beyond the midpoint on the guage with the a/c on, either around town or on the freeway. Went up to high desert today, in the high 90's, and on the long grade at 75-80 mph, with the a/c, the guage went within a block or two of the red. Also got hot around town with the a/c on. Recently replaced water pump and installed 180 thermostat, new antifreeze. Looks the like PO replaced the radiator within last year or so. Now I'm wondering if the car is a safe bet to drive to Vegas where a/c is essential. If if were just around town, I would look at fan. But since I also had a problem at 75mph, that should be pushing more than enough air to cool the engine, even at 98 degrees on a long but not terribly steep grade?

Best of luck - I went through 2 months of this, and while I never did find the problem, mine does cool back down at 'speed'.<P>Please keep us all apprised of exactly what you do and the results you obtain.<P>--Tom

Just curious, did the running hot occur before or after the water pump/thermostat change?

All repairs/mods made about a month ago and this happened today. Is the fan supposed to come on and stay on whenever the a/c is on? The only thing I did yesterday was take the instrument trim off and console apart so I could rebuild broken plastic mounts for the knee bolster and convenience cubby. I also removed the radio so I could see about repairing the tape deck. That did blow the #13 fuse and now driver's side headlight is out [comes up, thank heavens, but no light], but I am chalking the latter up to coincidence. . . I hope.

Just an update and thanks to those who responded. The headlight thing was nothing more than the connector coming off with the up/down action of the unit. The connectors are not terribly tight.<BR>Back in San Diego, running cool. Any comments from Phoenix owners? Do the cars run at the midpoint of the guage in 100+ heat with a/c on?

As far as I know, the A/C does activate the fans for air flow over the condensor, however, I believe the speed is controlled in response to the temperature and/or pressure of the freon.

Hooboy, what a can o'worms. Have come to a few conclusions:<BR>a) Reatta's do not have as much cooling capacity as other GM cars with the same drivetrain.<BR> radiator is about 3" (10%) shorter than that in a '90 Bonneville - orther dimensions about the same.<BR>c)There was a change in the fan system of the Reatta for 1989 not shared with Rivera/Bonneville through at least 1990. This placed both fans in series at LOW speed and in parallel if they went to HIGH.<BR>d) GM seems to consider anything under about 225F as normal.<BR>e) the front air dam is not sealed to the radiator support which permits considerable spillover. This reduces airflow through the radiator two ways - first by allowing the spill to bypass the radiator and second by raising the static pressure under the engine. On our Bonnevile, this area is sealed. Note: this will affect operation primarily over 30 mph.<BR>f) The Reatta is particularly sensitive to any blockage of the grille area and is evidently not a good "bottom breather" (see air dam). After installing a LeBra the temperature at 50+ increased 15-20F (was still going up when opened flap). Opening the license plate flap (no front plate in Florida) reduced the rise to 5-7F. Am having one modified to expose the full grille area. A similar bra had no effect on our 3800 TranSport.<P>The bottom line is that a combination of factors apparently makes the Reatta marginal on cooling and *any* weakness will cause the temperature to rise, particularly at low speeds, flow seems adequate above 50 mph however.<P>Have been dealing engine heat rejection for a long time (first B/P Covettes, then an RVEECO cooler on a VW camper - pulled the Cascades in fourth) and like to keep an engine cool - 180-185F is plenty for a computer car.<P>At the same time have found 100F over ambient to be a reasonable expectation. If you are in 108F weather in Vegas (but its a DRY heat...), keeping it under 200 with the a/c on is probably going to be a challenge & will probably require both fans on HIGH all the time. <P>Unfortunately unlike the Fiero which uses a simple switch, the Reatta HIGH fan is commanded by the ECM and on at 200/off at 190 (good settings for 180F thermostat) will require a PROM change. If going that far would probably set to turn off/revert to low above 50 mph also.<P>Two data points you might want to look at - you mentioned "the long grade at 75-80 mph" - are you talking about the climb headed East out of Needles ? In midsummer, that is one of the worst car-breakers in the US, even in tip-top shape the temp is going to climb, is worse than either Monteagle or the climb out of Cody Wy IMNSHO. <P>Would be more concerned about level cruising. Does the 90 has "instantaneous MPG" like my 88 ? If level cruise at that speed is under 25 mpg would be looking for a misfire/bad O2 sensor/steady knock sensor retard and any will drive the temperature up.<P>At any rate this is waaaay too long so say goodnight Dick.<p>[ 08-24-2001: Message edited by: padgett ]

Hi all ... for what it's worth, I saw the question regarding Phoenix owners. <P>For my 3 years in Phoenix, I had minimal problems with the cooling system until my last year there. As a rule, in hot (90+ weather), stop & go traffic, my 1990 always ran a little past top/center of the gauge. Then problems started during my last year there .... While having the problems diagnosed by Childress Buick, I was told that the first/easiest check to see if things are running properly (with the car parked & running) is to turn on the a/c & check to see if BOTH cooling fans are running. Evidently on the 1990, both fans should kick on when the a/c is turned on. If that's not happening ... there's a problem.<P>Since I replaced both fan motors (both of which had siezed), the car doesn't warm past mid-gauge while it's being driven in any temp weather.<BR>~Brenda

Brenda,<P>Was it evident that both motors had seized? Where they both not working AT ALL?<P>Just wonding - both of mine turn when the AC is on, albeit at slow factory speed (or appears to). Upon 109C, the fans go from low to high, and the temp drops accordingly.<P>--Tom

Hey Tom -<BR>The guess from the dealership on mine was that one fan had likely been out for quite a while, but I never had real cause to investigate until the 2nd one quite working & the car started over heating/red lining.

It is quite possible for fan motors to seize. My old 1986 Corvette kept having cooling problems and I never thought it was the fan. I checked the fuses, relays, all the wires, the coolant sensor, etc. I never imagined it could be the fan motor, but when I applied current directly to it, it wouldn't budge. Replaced the motor, voila problem solved. When you think about it, the fan motor does take a lot of abuse, running and stopping all the time, and running nonstop in hot weather.

Padgett, thank you for the detailed reply. I checked to make sure both fans came on when the a/c is on. They do. Will have to check to see if the go to high when the temp is hight.<BR>I did note that there was some very slight leakage where the bottom hose goes to the water pump. Tightened the clamp and hope that resolves the problem I created when I replaced the pump, lower hose, and installed a 180 thermostat.<BR>Even with the leak, the water level did not fall, though might not have been fully pressurized.<BR>Will have to review possibilities on sealing the air dam to improve cooling.<BR>One thing I am surprised about is that the fan does not stay on after the engine is stopped. Noted considerable heat soak, especially when the engine was more than 2/3 to the red.<BR>You're right, it would be nice to reprogram the prom to have the fans go to high at slightly lower temperature. I am not inclined to spend $200 on a new prom just for that, especially since most of the super chips require higher octane fuel.<BR>We have had some warm days here in San Diego, and still nothing above the midpoint. Maybe at 124K the engine is a little tired for long climbs in hot weather with the a/c running? Again, thanks to all for the ideas.

Well, at over 100k the timing chain has stretched a bit which means the timing is retarded some which will make an engine run hotter.<P>Still $200 for a Prom ? That is absurd, thought the going price was around $80. Considering that a 27C256 is a cupla bucks (maybe less) obviously you are paying for their expertise. <P>Have found some info on the GN site about their proms and looks like there manipulating the on-off, hi-lo fan settings should only be four or five bytes but will not know until I can map a stock prom. At least the ECM is much better documented than the BCM.<P>Having an 88 (ballast resistor on fan) thought I would try some simple experiments first like a Pep Boyz fan sensor clipped to the radiator to bypass the resistor at about 195F. That should be simple and cheap without affecting the ECM. Could also rejumper the relay block to turn pusher on full when puller is on half. This would provide some data points.<P>Really think the Reatta was shortchanged a bit in the cooling area and that is why it recived the "heavy duty" (V08) option from day one and the engineers played with that in 89 (why 89-up Reatta's have both fans turning at low - other GM cars with 3800 do not at least through 90).<P>Am having a few days at home but am reluctant to experiment with the good ECM in my car still seeking an experimental unit - may go junking this week.<P>But today am going around with Sears. The advt & on web says the AR07 & AR157 are on sale, $259 for 14x6 & 15x7 with "similar savings on other sizes" but the store says 16" are full list so have new windmill.<p>[ 08-26-2001: Message edited by: padgett ]