Hello Everyone,

So I have a 1985 with a 4+3 transmission and 60k on original L98 engine and transmission. Looking for some information on an apparent issue I am having.


I live in central Pennsylvania and I run my car as a daily driver when there is no snow or much salt on the road. My most normal drive is a 20 mile commute to work on a highway with half of it a 55mph speed zone and the other a 65mph zone. When it first started getting cold out I noticed that my engine temperature was getting increasingly lower while driving to work, even if I warmed it up for 10 or 15 minutes before I took it out it would still cool down as soon as I started moving.

Now before this I found out my overdrive will not engage unless the engine temp is above 138F-139F. I understand this is probably a correlation not necessarily a causation, but could anyone enlighten me on why this may be? This of course was not really an issue until it started getting cold.

On one particularly cold day (I think somewhere between 10F-15F I got on the highway and I found I could not get the engine temperature much above about 140F while driving in 4th. When I engaged the overdrive and the RPMs dropped it cooled down several degrees and then the overdrive disengaged.

I am pretty confident that my temperature sensor is not bad, as I can let it idle and it gets up as high as 227F and kicks on the fan. I can understand that a lot of this has to do with the real cold air getting sucked into the cooling system going 80mph down the highway, but is there anything I can do to get it running hotter? Could it be an antifreeze issue, or thermostat? Or is this something along the lines of "corvettes aren't meant for the rain, cold, and snow!!!"




thanks for your time.

 

you don't have a working thermostat if there is one in there at all

 

Yeah your thermo is missing or malfunctioning. My '85 did the same thing as yours. The temp must stay above 140* for the OD to engage. It will kick out when temps drop below this level. I thought my OD was going south before I found this out. Put in a new thermo, 160* or higher and problem solved.

 

Alright cool guys thanks! Guess I will put a new one in.

I see there are several discussions on which temperature thermostat to go with, 160, 180, or the OEM 195. I am thinking my best bet would be the 180, anyone have thoughts?


thank you.

 

oem for my 85

 

You have a stuck or missing thermostat for sure. I replaced my stuck stat with a 180 which really opens at about 172.

 

I have the same car as you. Stick with the stock 195 t'stat it originally came with. You are correct about the overdrive temperature. That's what the overdrive is designed to do if it's not warm enough. The cooling fan is coming on at the factory setting of 228 degrees. Completely normal. I'm close to you as I live near Pittsburgh. My car is now sleeping for the winter.

 

I was having the exact same problem which started about a month ago with my 85. You should also notice that the oil temp reading will stay on low. Put in a 195 thermostat last weekend along with new upper radiator hose and all is well..........and warm. Don't forget to replace the gasket. With a little perseverance the housing CAN be removed without taking the throttle body off.