cholliday07 Posted June 28, 2021 Share Posted June 28, 2021 I have searched for a few days on the Reatta forum for a decent answer and havent found anyone asking the specific question. I understand the 3800 likes to run a little warmer than others but I have not found what the digital gauge lines mean in terms of degrees or if I have something to worry about with my Reatta. I have a 1991 Red coupe that I have been completely taken back by, I love the car and all it has to offer but the digital temp gauge likes to move a lot more than I am comfortable with. Within the first 48 hours of owning it, I replaced the thermostat and pressure tested, the bars run about half way 90% of the time, now sitting at a redlight it starts creeping up. At a drive thru I will go 3 bars over half maybe 4. At this point I am at 3/4 of the gauge and cutting it off with fear of overheating. Can someone share some insight on if I have a problem or what the lines actually mean, I am currently looking for my old OBD1 reader to scan the data and actually drive with it a few days and record data but until then, this is the best way to find out. Link to comment Share on other sites More sharing options...
Ronnie Posted June 28, 2021 Share Posted June 28, 2021 Welcome to the forum! You won't need a scanner to check the data on your Reatta. It has a diagnostic system built into it. The Diagnostics menu at the top of the page will tell you how to access the onboard diagnostics and how to use it. Someone may come along with a '91 and tell you how many bars the temp gauge should show. 1 Link to comment Share on other sites More sharing options...
Padgett Posted June 28, 2021 Share Posted June 28, 2021 (edited) Like this ? 170F: one bar under center 180F: half way 210F - one bar over center 217F - two bars over center 221F - three bars over center I use a 180F superstat and reprogrammed the fans to come in sooner (high at 190F) usually runs about 185F. My experience is that it is a cool running engine if treated right. Also if you run it cool, everything under the hood lasts longer & the AC works better. Edited June 28, 2021 by Padgett 2 Link to comment Share on other sites More sharing options...
2seater Posted June 29, 2021 Share Posted June 29, 2021 As Ronnie mentioned, there is an onboard scanner that can be accessed from the drivers seat at any time. ED04 in the ECM data screen will give you a live reading of the coolant temperature in degrees C. The How To and Diagnostic guides in this forum are invaluable to getting a handle on the attributes of this car. Enjoy😎 Link to comment Share on other sites More sharing options...
ship Posted June 29, 2021 Share Posted June 29, 2021 Don't know about previous years (3800 LN3), but the '91 3800 L27 comes from the factory with a 195F thermostat and normal operating/running temp is 230F. The "half way" bar is around the 230F setting. Fluctuations in bar activity is considered normal as long as both fans are functioning correctly. As long as the indicator needle doesn't land on the last bar on the right, you're operating within the engine's temp specs. You might want to check that you have the recommended/correct thermostat, that the engine coolant and tranny fluid are fresh and at the correct levels, and that the radiator is flushed and flowing properly. GM service bulletins recommend that engine coolant be replaced every two years. Link to comment Share on other sites More sharing options...
Padgett Posted June 29, 2021 Share Posted June 29, 2021 GM has been using 195F thermostats since the 50's. However warranties are of limited duration. I found years ago that running cars cooler (160F thermostat in a non-computer car, 180F in a computer car) and bringing the fans in sooner not only makes everything under the hood last longer (have had my 88 Reatta for 20 years now), the AC also works better. Said before but bears repeating. ps 180F thermostat provides plenty of heat even in below 0F conditions 1 Link to comment Share on other sites More sharing options...
ship Posted June 30, 2021 Share Posted June 30, 2021 Have never had any problems with two '91' Reattas and two '92 Rivieras keeping with factory settings. 1 Link to comment Share on other sites More sharing options...
Padgett Posted June 30, 2021 Share Posted June 30, 2021 You realize the "factory setting" turns the HI fan on at 217F ? For me anything over 200F is just Too Hot. 1 Link to comment Share on other sites More sharing options...
Ronnie Posted June 30, 2021 Share Posted June 30, 2021 I agree with a cool running engine ( I have a 170* thermostat) but a stock cooling system in good condition is capable of keeping the engine cool enough to prevent damage to the engine. 1 Link to comment Share on other sites More sharing options...
DAVES89 Posted June 30, 2021 Share Posted June 30, 2021 I run a 185 and also have that harness that Mc_Reatta made for me to run both fans all the time, so I have that going for me which is nice. 1 Link to comment Share on other sites More sharing options...
Ronnie Posted June 30, 2021 Share Posted June 30, 2021 45 minutes ago, DAVES89 said: I run a 185 and also have that harness that Mc_Reatta made for me to run both fans all the time My '88 is a little different but I did the same thing by jumping a resistor on my low speed fan to make it run on high anytime the AC is on. That really helped when sitting at a stop light. Link to comment Share on other sites More sharing options...
BlakesReatta Posted June 30, 2021 Share Posted June 30, 2021 My 1990 usually sits at the halfway mark going down the road. I do notice that if you let the car idle for more than five minutes it will creep up to around 3/4 toward the hot mark. It has never overheated, not even in 100+ degree weather. 2 Link to comment Share on other sites More sharing options...
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