Engine Temps

[mhuppertz]

My wife is having to drive the Reatta ('89) while I do head gaskets on her Jeep, and the temps are going up to an indicated 240 in town, but back down on the freeway. The thing is, it is not boiling over.

I replaced the thermostat, has a new radiator (aluminum) and hoses. The fans seem to be kicking on normally too.

Is the sensor a drama queen?

She just got home, and unlike the Reatta she was boiling over because she turned the air off to keep it from reenacting the China Syndrome.

 

Bad sensor? Fans not working at 100% capacity? Help a brother out!

 

Thanks!

 

Mark

[Barney Eaton]

I don't think you have a problem.

It is fairly common for the indicator to show hotter than normal in traffic, summertime, with the a/c on.  (information for others with Reattas...the 1988 & 1989 Reatta gave an actually coolant tempature,

in 1990 the cluster was changed and the gage has no numbers, just "C" on the left and "H" on the right, on the later cars, normal is straight up on the gage)

Check both cooling fans to verify they are both running......the one in front of the radiator should turn on anytime you have the a/c on.

most of the time the fans are both running but at 1/2 speed because the electrical circuit runs them is series.....until the coolant temp get to around 230, then a relay is triggered and both fans see 12v and run at full speed.

You need a service manual to do further diagnostics .........I am attaching the schematic from the 88-89 on first... the other one is a '91 , it might be slightly different for other years.  

Sorry about the quality of the first one.........

Edited June 8, 2017 by Barney Eaton (see edit history)

[mhuppertz]

Thanks much Mr. Eaton.

I told her to ignore it.

Really appreciate the feedback!

 

[89RedDarkGrey]

Don't worry about it-

 

But don't ignore it, either.

 

If it gets too crazy- turn heat on HI, put down windows, pull over, park, idle till cooler, wait outside, call you.

[drtidmore]

As has been mentioned on this forum before and confirmed by a Buick powertrain engineer, the engine itself is quite happy at 230 degree.  It is the transmission that should be your concern.  Transmissions do NOT like heat and anything above 190-200 is grounds for concern.  Yes, the tranny cooler IS on the cooler side of the radiator so that side is bit below the engine temp, but still, 240 means that maybe the cooler side is 15 degrees cooler.  It is normal for the engine to register higher in A/C on, stop and go summer city traffic, but 240 is above the norm for even those conditions.  The only time I have even seen temps near 240 was when I had a fan relay failure and only the puller fan was working. As Barney pointed out, verify those fans first as I suspect that they are NOT switching into high speed.  

 

Going back to the transmission, I would pull that 195 thermostat and at the very least drop to a 180.  There is a 160 degree that will drop in as well, but it tends to not keep the engine hot enough in mild to cold temps to allow the ECM to go into closed loop.  I researched and found that the 170 degree, HyperTech Power Stat #1007 (got mine from Summit Racing) can have its perimeter ground down to fit perfectly into the Reatta thermostat housing.  This allows the engine to run a LOT cooler, still go into closed loop mode, and keeps the tranny temps down where the stress is a lot less.  

 

I might add that I went the extra mile and modified my cooling fan circuit to allow me to set the high speed kick in temp without having to resort to a custom ECM prom.  I have High Speed now set to kick in at 180 and back to low speed at 170 and the highest temp since the thermostat and cooling fan mod has been 184 and that was for just a brief couple of minutes just as the fans switched to High Speed which brought the temp back to 172 in short order.

 

If this were my Reatta, I would NOT be ignoring 240 degree temps under any condition!

Edited June 8, 2017 by drtidmore (see edit history)

[89RedDarkGrey]

I concur- I would install the modified 170*F thermostat, and change the who-knows-how-old coolant temperature sensor, a very critical part in our cars, '88-'91. These do wear out, without warning.

 

Easy tutorial for the modification of the 170*F unit (thank you drtidmore & Ronnie) is HERE 

Easy tutorial for the installation of a thermostat is HERE

 

Coolant temperature sensor is HERE

Edited June 8, 2017 by 89RedDarkGrey (see edit history)

[DAVES89]

On the Red which is my summer only Reatta I installed a tranny cooler [which mounts on the front of the radiator] and bypassed the radiator completely. I also have a 180 degree thermostat and a "Mc_Reatta fan switch" that runs the fan on high. Yesterday we were about 90 degrees with moderate humidity and never hit 200 degrees.

[ChrisWhewell]

I drove a 93 vette for a decade and it was normal for operational coolant temp to be up to 237 deg. before the fans would kick on, that was the design spec