Thermostat replacement

98 softtail · 05-11-2007, 11:01 PM

OK, I know this subject has been talked to death but I have to ask one more question.
In the service manual it states that the TS and housing must be replaced as a unit, that the TS is not servicable. It seems that thermostats are available seperatly so what gives on this. Can I replace the thermostat with one from a parts store?
Any help on this would be great.

Thanks,
Joe B.

THOR · 05-11-2007, 11:23 PM

Hi Joe, I just had my stock thermostat replaced with a 160 degree and it looked liked to me that only the thermostat unit was changed. I think Backyard Mechanic could answer that question better. Good luck. Mark

**Rich Z** · 05-12-2007, 01:19 AM

From what I have heard, the 97-03 C5 has the tstat and housing as one unit. But the '04 has them separate so you can just replace the tstat itself.....

Possibly replacing the entire unit with an '04 tstat and housing would be a wise move.....

Honestly, I think you could get a cooler running engine in traffic if you just programmed the fans to come on at a lower temp. Just about everyone says you MUST do the fan reprogramming with the 160 tstat anyway, but I think you could just skip the hardware replacement and just go for the programming alone to get the same result.

davekp · 05-12-2007, 09:52 AM

Quote:

Originally Posted by Rich Z

From what I have heard, the 97-03 C5 has the tstat and housing as one unit. But the '04 has them separate so you can just replace the tstat itself.....

Possibly replacing the entire unit with an '04 tstat and housing would be a wise move.....

Honestly, I think you could get a cooler running engine in traffic if you just programmed the fans to come on at a lower temp. Just about everyone says you MUST do the fan reprogramming with the 160 tstat anyway, but I think you could just skip the hardware replacement and just go for the programming alone to get the same result.

The 97-03 thermostat assembly is not interchangeable with the stats from 04 on. For the 04 on, you do not have to replace the housing when changing the stat.
You do not have to reprogram the fans to get some advantage of a 160 stat. With a 160, you will cruise at a lower temp, and thus take longer to get up to fan turn-on temps in traffic. But in prolonged traffic, you won't run any cooler without reprogramming.

**Rich Z** · 05-12-2007, 01:07 PM

Hmm, seems I read somewhere that people with 97-03s were using the 04s. Guess that info was wrong.....

I guess maybe I need to put in a 160 myself just to see what happens. I still believe that the thermostat only controls when it opens up to allow full cooling flow and has nothing at all to do with the operating temperature of the motor. The 160 degree thermostat does not allow MORE coolant flow than a 180 degree one does. The 160 only opens up sooner than the 180 when the motor is warming up. Up till the coolant temp reaches 160 degrees (more or less) the thermostat is CLOSED, allowing the coolant within the motor to come up to operating temperature quickly. With the 180, the coolant temps within the motor need to reach 180 degrees (more or less) before IT opens up.

But I have heard so much conflicting info from people that it is pretty tough to figure out what is going on.

davekp · 05-12-2007, 04:59 PM

Quote:

Originally Posted by Rich Z

Hmm, seems I read somewhere that people with 97-03s were using the 04s. Guess that info was wrong.....

I guess maybe I need to put in a 160 myself just to see what happens. I still believe that the thermostat only controls when it opens up to allow full cooling flow and has nothing at all to do with the operating temperature of the motor. The 160 degree thermostat does not allow MORE coolant flow than a 180 degree one does. The 160 only opens up sooner than the 180 when the motor is warming up. Up till the coolant temp reaches 160 degrees (more or less) the thermostat is CLOSED, allowing the coolant within the motor to come up to operating temperature quickly. With the 180, the coolant temps within the motor need to reach 180 degrees (more or less) before IT opens up.

But I have heard so much conflicting info from people that it is pretty tough to figure out what is going on.

Not exactly.
First off, a "160" stat does not open at 160. It begins to open at some slightly higher temp and opens over a range of about 15 degrees.
The C-5 and C-6 cooling systems have the capacity to maintain a steady state engine temp below 180 degrees AT CRUISE. The thermostat modulates to maintain it's temperature.
A 160 stat will maintain about 180 AT CRUISE.
A stock stat, Call it 186 or 195, whichever you prefer, will maintain about 196 AT CRUISE.
If someone made a "140" stat I'd guess you could maintain a cruise temp below 175, whatever the limits of the cooling system are.
IN TRAFFIC, the temps will go higher, depending on fan settings. Remember also that in traffic we typically Idle so COOLANT flow is less than at cruise.
As far as early/later model stat interchangeability goes, I know the early model will not go into the later model water pump housing. I have not tried putting the later model into the early pomp housing, but it looks like it will not go. Even if it does, you'll need to buy a late model stat housing to go with the later model stat, and the cost will put you in the range of a "correct" early model stat.

**Rich Z** · 05-12-2007, 08:12 PM

Well, I guess the biggest question in my mind is whether a running motor can actually drop the temperature BELOW the operating trigger of a thermostat while cruising. That is the only way a thermostat can actually regulate the temperature of the coolant in any meaningful way after it has opened up fully once the full operating temperature has been reached. In order for the thermostat to close, even partially, the coolant temp must drop below it's rated operating temperature. Once it has opened up, then the operating temperature of the motor is pretty much controlled by the cooling efficiency of the radiator and the ambient air temperature going through it.

So I guess the question in my mind is if a 160 degree thermostat is fully open and a 180 degree thermostat is fully open, is there any difference in the running temperature of the motor? If there is a difference, WHY?

The only way I could see it being so is if the coolant flow through the 160 degree is greater than through the 180. And even then, there must be a point of diminishing returns, as coolant going through the radiator TOO quickly (via too much flow through the thermostat) would not be able to shed it's heat before being pumped back through the motor.

davekp · 05-13-2007, 08:11 AM

Quote:

Originally Posted by Rich Z

Well, I guess the biggest question in my mind is whether a running motor can actually drop the temperature BELOW the operating trigger of a thermostat while cruising. That is the only way a thermostat can actually regulate the temperature of the coolant in any meaningful way after it has opened up fully once the full operating temperature has been reached. In order for the thermostat to close, even partially, the coolant temp must drop below it's rated operating temperature. Once it has opened up, then the operating temperature of the motor is pretty much controlled by the cooling efficiency of the radiator and the ambient air temperature going through it.

So I guess the question in my mind is if a 160 degree thermostat is fully open and a 180 degree thermostat is fully open, is there any difference in the running temperature of the motor? If there is a difference, WHY?

The only way I could see it being so is if the coolant flow through the 160 degree is greater than through the 180. And even then, there must be a point of diminishing returns, as coolant going through the radiator TOO quickly (via too much flow through the thermostat) would not be able to shed it's heat before being pumped back through the motor.

Since the stat opens over a range of temperature, it begins to close at about the same temperature it became fully open.
You just need to take a stat, put it in a pan of water, and heat it up. Monitor the temperature at which it begins to open, reaches fully open, then turn off the heat and watch as it begins to close, and then finally reaches fully closed.
Sorry to say, but much thermostat discussion is based on speculation and guessing.
Do the test and see what happens.
Also, put a 160 in your car and SEE what happens.

ADulay · 05-13-2007, 10:56 AM

Kindly notice how I have cleverly stayed out of the traditional thermostat thread this time!!

AD (with the stone stock cooling system)

"Backyard Mechanic" · 05-13-2007, 12:26 PM

Quote:

Originally Posted by 98 softtail

OK, I know this subject has been talked to death but I have to ask one more question.
In the service manual it states that the TS and housing must be replaced as a unit, that the TS is not servicable. It seems that thermostats are available seperatly so what gives on this. Can I replace the thermostat with one from a parts store?
Any help on this would be great.

Thanks,
Joe B.

Joe,In short,Yes you can just replace only your thermostat,and yes you can get it from a local auto store.But I would advice you if your Vette is a daily driver,I would get the fans programed so they come on at a lower temp.If it is not a daily driver just changing the ts will lower your coolant temp. about 10-15 degree.I will be doing this soon,but I will also get the fans to come on sooner,mine is a daily driver.The stop and go traffic in the summer is a bastard on the motor,and I like to run the AC.Good luck with it

,O how was the track?Rob