Mike951

Is it ok to run the car without a thermostat(944)? The car overheated last week and I don't think much damage was done, so i wanted to try and start it?

Skip

for temporary use - should be fine. Some folks take them out completely... I think that's a bit risky.

S

PerceptionProblem

What would be the risks, assuming one lived in an area that was warmer than colder (So-Cal) I'm having issues with mine and thinking about running without one and seeing how she does. But I don't want to damage the engine, as it's my daily driver.

ArcticSteve

I ran the 924s for summer with no thermo. No issues.

xsboost90

taking the t-stat out changes the effective flow of the coolant. I would put a new one in. Someone explained this awhile back and it made sense.

MAGK944

Taking the thermostat out will make you engine run hotter, it's all about flow as xsboost90 said. The best way to describe it is that thermostat acts as a restrictor. Even when fully open it restricts the flow to the radiator slowing the flow and allowing the radiator to have time to cool. Without it the coolant would flow quickly through the radiator and back to the engine with little cooling. Also your fans would run more often as the sensor would see a consistently higher temp at the radiator. Another negative is that your engine would take longer to reach normal operating temperature when you first start the car. When your oil is cold it's not a good thing. The thermostat keeps the coolant out of the radiator on cold starts allowing the engine to get up to normal temperature quickly.

Oddjob

For greater heat transfer, the higher the flow, the better. Turbulent flow has a significantly higher heat transfer coefficient than laminar flow, so high velocity is absolutely preferred, both for cooling the fluid going thru the heat exchanger (radiator) and for absorbing heat from the head/block.

If you look inside the water pump, behind the therm, you will see a rubber seal and some cavities/flow channels. When the therm is closed, the coolant recirculates thru the block. When the therm fully opens, it pushes the plunger up against that internal rubber seal and closes the recirculation path, so all the coolant is pushed thru the radiator. W/o the therm, the recirc path is never blocked off, so you get partial flow thru the radiator and partial recirculation.

No big deal to run w/o a therm for testing or for limited use, but if you are driving hard (track use) or in a real hot area, the car can actually overheat when run w/o a therm. And as mentioned, you do want the engine to get up to operating temp as soon as possible.

Woody

What Magk944 said is spot on and about how my radiator repair guy explained it. The liquid has to spend some time in contact with the heat in order to absorb it and take the heat to the radiator. I suspect there is a reason why vehicles come with a stat.
Woody

Tedro951

1. Water moving faster will cool better. Hanging out in the radiator wont help.
2. Delaying the warm up without a thermostat isn't usually a good idea.

Cochezz

This is correct, use a thermostat for the street, for racing you can remove it but you have to block the holes that allow for the warm up flow path when the stat is closed. Otherwise you will never have complete flow thru the rad. On a race car air flow to the rad is adjusted (with tape usually) to controll the temp.

So use the stat, if your car is over heating you have other issues.

Tedro951

When you say it overheated last week, were the fans running, system full and bled, any recent loss of coolant (other than the overheating event)?

PerceptionProblem

I totally hijacked this thread, as I was searching for the very answers everyone gave me. (The original post was from 2003)

My system tends to get fairly warm, and I found out that one of my fans (I have an 85.5 n/a 944) doesn't run at all. I have reason to believe that my fans are the culprit; as the original owner fancied himself a handyman and rather than replace parts when they stopped working or otherwise broke, he would just bootleg a fix. So on top of needing to replace my fans, I need to re-splice a proper connector to the passengers side of the fan-harness.

I've also replaced my temp sensor, and am working on fully and properly bleeding the system again. I just don't have a place to properly incline my vehicle, so I'm taking it to a local mall that has a multi-level parking structure to use that slope. ^______^ I'm also a bit nervous about getting too much coolant on the block, as I don't want to ruin anything.