Overcooling ?

Hey everyone, first of all I would like to thank everyone on the forums for their efforts in sharing their experiences and helping each other out. I have been a lurker here for the last few days while my membership was approved learning as much as possible about the car I was about to purchase. In short, Hi, I'm new.

I recently purchased a 94 with 16K miles that has never seen a bad day. The car has had the head gaskets replaced (by whom and with what I don't know) and otherwise had all of its maintenance. I plan on going through an flushing all of the fluids including gearbox, diff, coolant, brake, power steering and blinker fluid over the next few weekends. I am a car collector of sorts and enjoy driving everything as much as possible- the Viper being no exception.

That said, I spent hours digging through posts about overheating and thermostat recommendations, fan kick on temps and the works- however my issue appears to be the opposite. When around town and traffic the temperature sits pretty and stays near the yellow however on the highway at 75-80 the temp slowly drops down to near nothing until I resume normal in city driving again. When the car sits overnight and I go in the morning to war it up, it does so quickly and when left to run at idle for about 15 minutes even cycles the radiator fans.

My concern is possible damage to the engine from overcooling or major temperature swings with varied driving. Of the possible scenarios I thought it could be a stuck-open, bad or otherwise missing thermostat, bad temp sender or disgruntled gauge. I plan to temp gun the radiator when this is going on to see if there is actually a temperature difference or if the car is just poking fun at me. Has anyone had this sort of issue in the past? Thoughts? I included a photo of the gauges while cruising at 75-80 after about 15 miles.

Thanks all! (ps, sorry if I am posting this in the wrong area or improperly posting images, let me know!)

Sounds like one cool Viper. That's a good question. Whenever I'm cruising down the highway for any length of time (and my car is supercharged) my temps get down around 120... Stop and go traffic it fluctuates between 195 and 205.

Free2go said:

Sounds like one cool Viper. That's a good question. Whenever I'm cruising down the highway for any length of time (and my car is supercharged) my temps get down around 120... Stop and go traffic it fluctuates between 195 and 205.

Click to expand...

must have a problem with the thermostat. Once warmed up, the minimum temperature should be pretty close to the thermostat rating.

Free2go said:

Sounds like one cool Viper. That's a good question. Whenever I'm cruising down the highway for any length of time (and my car is supercharged) my temps get down around 120... Stop and go traffic it fluctuates between 195 and 205.

Click to expand...

This sounds like what mine does as well. Have you ever had your T-stat replaced or is it the factory one?

I haven't had any over heating issues so I never thought about it. Running cool on the highway is a pleasant feeling. I think after a year of scouring the forums I would have seen something regarding over cooling, but have not. Doesn't mean it's not an issue though.

Free2go said:

I haven't had any over heating issues so I never thought about it. Running cool on the highway is a pleasant feeling. I think after a year of scouring the forums I would have seen something regarding over cooling, but have not. Doesn't mean it's not an issue though.

Click to expand...

Replace your thermostat. That's its function -- it's probably stuck open.

The Gen 1 cars tend to run hotter than the rest. There are numerous things that can push it over the edge. Feel free to call me and I can go over this, there are quite a few things to check and numerous things you can do to improve the cooling system. 310-597-6295

Will definitely look into it. My radiator and fan are not stock. They have been upgraded. Temperatures are constant until I get on the highway then they drop considerably...especially when its cool outside.

I do however have a rattling in the rear of the car and was told by one of the guys at the dealership I needed some muffler bearings. Does VPA sell those?

Are you sure your gauge is correct....

The early Vipers did not use a muffler bearing, but 92-early94 used a spring and conical washer mount for the rear muffler hanger that often made noise. You can change to the later rubber mounts or fabricate some muffler bearings and hangers, JC Witney sells those.

Viper98912 said:

Are you sure your gauge is correct....

Click to expand...

Nope, not sure at all. It is one of the things I am going to be diagnosing before tearing into it and replacing the T-stat. I posted this to see if anyone had had any overcooling issues and what the remedy was or if there were known issues with the gauge or sender.

Dan Cragin said:

The Gen 1 cars tend to run hotter than the rest. There are numerous things that can push it over the edge. Feel free to call me and I can go over this, there are quite a few things to check and numerous things you can do to improve the cooling system. 310-597-6295

Click to expand...

Thanks Dan, although I don't have an overheating issue (yet)- but quite the opposite.

Hey Dan...did you play football there in California? My cousin and I played at RCC before we moved on and he said partied with a Dan Cragin from what he remembered was Rancho Santiago.

W3R3W0LF said:

Thanks Dan, although I don't have an overheating issue (yet)- but quite the opposite.

Click to expand...

What ambient temperatures are you talking about ? If you are in Phoenix/Tucson/Yuma type areas; you, certainly won't be talking about overcooling issues in a few months ! Dan is certainly highly qualified/experienced to address your questions especially if you are trying to sort this out yourself. If you want to take it to someone in AZ to check it out, Eddie Martin at Bill Luke Dodge in Phoenix is at the same level as Dan C, I think.

AZTVR said:

What ambient temperatures are you talking about ? If you are in Phoenix/Tucson/Yuma type areas; you, certainly won't be talking about overcooling issues in a few months ! Dan is certainly highly qualified/experienced to address your questions especially if you are trying to sort this out yourself. If you want to take it to someone in AZ to check it out, Eddie Martin at Bill Luke Dodge in Phoenix is at the same level as Dan C, I think.

Click to expand...

I am trying to sort out an overcooling issue right now as it indicates some kind of issue (probably with the T-stat) even if during the summer the temps are hot and it indicates normally later. I was a mechanic by trade before my current profession and was curious to see if the overcooling was a known issue / common problem with the first generation vipers or if it was just my particular car. I wasn't sure if there were known gauge issues or temp senders or common T stat failure or ?? with this generation viper and that is the info I was after. So far it seems that my issue is not common and isolated to this car.

Thanks for your responses guys!

PS, I will keep Dan in mind for future issues as well as Eddie. Thanks again

Eddie is awesome.

Mine does the same thing as yours. I rather have it cool than over heating. I think its just bad calibration between the cause and the sensor.

brentsGTS said:

Eddie is awesome.

Mine does the same thing as yours. I rather have it cool than over heating. I think its just bad calibration between the cause and the sensor.

Click to expand...

Engines really should run at the temp they were tuned and designed for. I have heard of premature cylinder wall wear due to running too cool and the engine temps clashing. Not sure how much truth there is to that but it would still be nice to see it maintain proper temp. Interesting to see it happen to two other Vipers now- I wonder if indeed it is a sender/ gauge issue. Have you ever replaced your T-stat or noticed any drivability issues?

W3R3W0LF said:

Engines really should run at the temp they were tuned and designed for. I have heard of premature cylinder wall wear due to running too cool and the engine temps clashing. Not sure how much truth there is to that but it would still be nice to see it maintain proper temp. Interesting to see it happen to two other Vipers now- I wonder if indeed it is a sender/ gauge issue. Have you ever replaced your T-stat or noticed any drivability issues?

Click to expand...

much colder than engine specs/design is as bad than overheating. #1 issue would be the lubrication, you have moisture in the oil and that need to be removed by having the oil hot enough.

Keep in mind that there are two temp sensors...one for the gauge and one to the controller. You might just have a bad/dirty connection to the temp gauge. It might be worth a try to unplug it at the sensor, clean contacts, reconnect. As you know, t-stat and sensors at rear of engine...would be ready to change sensor and T-stat.

Steve-Indy said:

Keep in mind that there are two temp sensors...one for the gauge and one to the controller. You might just have a bad/dirty connection to the temp gauge. It might be worth a try to unplug it at the sensor, clean contacts, reconnect. As you know, t-stat and sensors at rear of engine...would be ready to change sensor and T-stat.

Click to expand...

Thanks for the advice, if I can get to it without pulling things apart I will clean the sensor connection and see what's up. If not, I will just pull it apart and replace all the things. All of them.

Umm my thermostat is at the front of the motor.

Gen I cars...T-stat at rear...all others are in front.

Tested a few things out and it appears that the T stat is either stuck open or missing as the gauge and sender are working to spec and the heater becomes lukewarm at best when the temp drops on the highway. Looks like the V will be getting a new T stat and coolant flush after all. Thanks for the relevant replies everyone : )

W3R3W0LF said:

Tested a few things out and it appears that the T stat is either stuck open or missing as the gauge and sender are working to spec and the heater becomes lukewarm at best when the temp drops on the highway. Looks like the V will be getting a new T stat and coolant flush after all. Thanks for the relevant replies everyone : )

Click to expand...

You probably have your preferences; but, I used what was recommended here: http://forums.viperclub.org/threads/580332-180*-Thermostat?p=2139193

I don't really see an advantage here in AZ in going to a cooler than stock thermostat; but, I did it anyway. The "Viper Wizard" has lots of experience, so, I took that recommendation for the 180 Tstat.

When I changed mine out, I did a test just to see the difference between the Mopar and NAPA 180. I put them in boiling water to open them up and make the following picture. Looks like the NAPA one would have the ability for a higher flow rate.

AZTVR said:

You probably have your preferences; but, I used what was recommended here: http://forums.viperclub.org/threads/580332-180*-Thermostat?p=2139193

I don't really see an advantage here in AZ in going to a cooler than stock thermostat; but, I did it anyway. The "Viper Wizard" has lots of experience, so, I took that recommendation for the 180 Tstat.

When I changed mine out, I did a test just to see the difference between the Mopar and NAPA 180. I put them in boiling water to open them up and make the following picture. Looks like the NAPA one would have the ability for a higher flow rate.

Click to expand...

Interesting. I read through a good deal of posts on here about the temp differences and I haven't made my mind up either. I was going to default to 195 if I had to make a quick choice however NAPA only seems to carry the 180 here. As for the image (thanks for that!) I wonder if the T-stat has been replaced and the extra flow from an aftermarket one is causing the issue. How do your temps run on the highway in the cooler weather?

W3R3W0LF said:

Interesting. I read through a good deal of posts on here about the temp differences and I haven't made my mind up either. I was going to default to 195 if I had to make a quick choice however NAPA only seems to carry the 180 here. As for the image (thanks for that!) I wonder if the T-stat has been replaced and the extra flow from an aftermarket one is causing the issue. How do your temps run on the highway in the cooler weather?

Click to expand...

The car still ran in the 185-195 range

I have had nothing but problems with those Stant-Wierstat thermostats. Try Cal-Therm if you can. Its the factory type.

Dan Cragin said:

I have had nothing but problems with those Stant-Wierstat thermostats.

Click to expand...

Any specific symptoms to be on the look out for ?

Issues I had were with the thermostat sticking or the spring popping out on top.