What Degree Thermostat?
 

hello, iam lookin' to buy a new thermostat and they come in two degree settings: 75 Degrees and 83 degrees. which one do you think i should purchase?

I think 83C is the factory part, Pelican sells it for $17.50 and free shipping.

Makes sure to get the two seals.

how come the inner seal is only for 83 and on? what am i supposed to use?

Do you have an original water bridge, guessing it could be related to a superseded part?

Pics always help to determine unusual set ups. No excuse, buy a cam for yourself and let the wife have her own ;)

just brought one from porsche and its 83 degrees

regards

geoff

ps dont forget the sealing rings

well no its not a set up type thing, its what pelican parts says. the inner seal is only for 83 and up and mine is an 82. thats why i ask about it.

lower temp allows more timing advance(or boost), higher temp fosters more complete combustion.

Pick one.

For a blown car i'd reccomend a 75. For a N/A, it probably doesn't even matter.

change your coolant to Evan's Cooling NPG+ and forget about temps---

it doesn't boil below 375 degrees, allowing for higher temps to be run without the risk of boiling over (like 50/50 water-antifreeze does).

not cheap at $32 per gallon, but the savings in head gaskets, busted hoses, corroded cylinder towers, etc., make it worth the price.

--Russ

Russ, this goes back to 1992, so things may have changed, but I tried that Evans Cooling with the 100% PG coolant in a turbocharged VW Scirocco, and it didn't work.

I ordered the kit, installed it properly....and then discovered that the car overheated incessantly. I called Evans [Mecca, back then], and they were a little perplexed, since my description of the installation was exactly what they described. In the end, I had to remove the coolant and parts and convert back to regular coolant. I suspect that since my radiator was original [90k+ miles], along with the water pump, that there was not enough coolant flow any more. They told me on the phone that the people who had had the most success with their system were running special radiators with larger tubes and much larger water pumps. It seems this system requires much greater coolant flow in order to work properly.

Since the majority of 928's are now quite..."vintage", and have cooling systems in various states of tune...that the Evans system wouldn't be a good choice.

N

Hey Sniper-

I have the 75 degree thermostat in my '85, and I am going to replace it next month with an 83 degree model. Why? Two reasons:

1. I drive around Fort Lauderdale, largely in traffic. And I only drive my 928 about 2500 miles per year. But 10 miles per gallon? :eek:

2. Logical fallacy. The 75 doesn't give you any real advantage over the 83. Think about it: if you install a 75 degree t-stat...is your radiator any bigger? Does your water pump suddenly pump more gallons per hour? No. You have an 8 degree buffer. 8 degrees? I suspect an M28 can eat that up in seconds, and the boostards even quicker. But driving around town normally, your engine is paying tickets the the "heat police". You are violating the thermodynamic laws, and you are now paying your tickets at the courthouse known as "Chevron".

N!

If you change the thermostat to 75C you should also change the cooling fan sensor in the radiator to the same temp or you will see no real cooling gains, especially when driving in traffic.

Dennis

I use the 75c in all my/past current 928's: I think it helps a little. I agree with the coolant amount/BTU's to offset: so I re-arrange my pressure switch wires on the 4-prong plug at my drier so that my condensor fan runs with my ignition switch: this DOES help in reducing heat & keeping the car cooler. Typically, I see the temp gauge needle about 3/32" lower than w/o the fans rearranged.

Every change you make from stock makes a car a bit more flaky, and harder to diagnose problems.

In theory I agree, but this appears to be a no-brainer. Many Austin 928er's have tried this & agree that it's a nice cooling "addition".

Mark

since it has been 17 years since your less than great experience, yes, things may be much different.

Technology changes every day----

--Russ

Mark, you don't have to do that. The fan is on the battery bus. On the lower corner of the radiator, on the drivers' side, there is a temperature sensor. simply bridge the two prongs of the harness and your auxiliary cooling fan [the "bird cage" fan at the front of the radiator] will run whenever the key is in the ignition position. I like this feature because this allows the fan to run for a few seconds before and after I start/stop the engine, and if the fan belt breaks, the car will not overheat. When I start it up, I let it run for a few seconds before I turn the engine over in order to blow out any gas fumes. Bilge blower-

N

Valid point.

But the laws of thermodynamics don't. Propylene glycol will not absorb or dispense with [carry] any where near as much heat as water, or even water/glycol mix. Unless the radiator is larger, or more efficient, or you have much greater water and air flow.

Do you have the Evans cooling system in your 928, and is it working?

N

-One thing I have done, and will continue to do...is to install a 7 psi pressure cap on my coolant reservoir.

Why?

To protect the rubber hoses. The cooling system seldom sees the 13 psi that the cap allows, but if you are stuck in traffic on the expressway on a hot day, you might just get up there. If you have a weak hose at all, suddenly you are standing next to your car in the breakdown lane, steam rolling out of your hood. I change my hoses every 5 years [due this year; next month], but it is still possible for something to happen. Hoses are killed not by pressure, but by heat-cycle. So many cycles, and instead of the 150 psi that they were capable of holding when they were new...suddenly they fail at 13 psi. The curve of degradation is probably steep. The 7 psi cap allows the system to boil-over instead of break a pipe. Now I do a lot of maintenance to my 928: basically, every day I am home I open the hood and inspect the whole engine area, but I cannot see the inside of the upper and lower coolant hoses to see if they are intact. What's more, the heater core hose [short as it is] needs constant attention, since it was designed as the weak link, due to torque-rock.

If you get into a bad traffic jam in the middle of the summer at 95 degrees F, and you are sitting there in your air-conditioned 928....with a 7 pound radiator cap, if there is a flaw in your coolant or radiator, then instead of blowing a weak hose, your car will start to steam and you will see it curling around the radiator. You pull over, and let it cool. The accident a mile in front of you clears, your car cools down, and you drive away....thinking about your order to Pelican or 928 International or 928 Motorsports or 928 Specialists along the way. Time for some new coolant...and time for some new hoses.

N

the issue is boiling point. there is no water, so the boiling point is raised significantly.

this allows for a higher operating temp, promoting better and more complete combustion and better fuel mileage. some would argue that it provides more power as well. as the boiling point temp is raised by the coolant, the need for high pressure systems (that raise the boiling point) become unnecessary. a low/no pressure radiator cap can then be used relieving stress on headgaskets/water pumps/hoses/radiator tank seals and the like. as there is no water in the system, corrosion should be lessened as well (tops of cylinder towers comes to mind).

Now, if your cooling system isn't up to the task, such as a clogged radiator or fan hub that doesn't work, then just changing the coolant may not help much.

No, I do not currently run the Evans in my 928, as the engine is out and may not go back in until sometime next year. I will try it though, as well as in one of my 18 wheelers that is currently undergoing a headgasket repair.

--Russ