Curious how our thermostat works

[macdude357]

I had my water thermostat replaced the other day. Out of curiosity, I was looking at the old one, I don't see how it actually seals off/opens up to allow the water to pass or not. I get that the little brass? rod moves as the water heats up/cools down but I don't see how that actually prevents or allows the water to flow.

Can anyone explain it?

Thanks!

[kevin @ eas]

Originally Posted by M3Post

The s65 thermostat looks a lot different than that traditional style where coolant is blocked off until a certain temp is reached. The s65 thermostat is open without a coolant block off like this

[macdude357]

Originally Posted by kevin @ eas

The s65 thermostat looks a lot different than that traditional style where coolant is blocked off until a certain temp is reached. The s65 thermostat is open without a coolant block off like this

Exactly. That's kind of my question. So does coolant always flow? If so, when the thermostat "opens" or "closes", what's actually going on? I still don't see how the thermostat would affect the flow at all given the open design.

[DukeofAlexandria]

So this does actually open, and then expand WITHIN the housing unit.

If you take a look here...

https://www.turnermotorsport.com/f/p...SABEgK6hvD_BwE

You can get a better picture of what is going on. The upper ring (the largest ring in the housing) sits on the metal dual hose housing on top of the motor. The back 'cup' housing sits in the back. They are connected by the springs and that's it - two seperate pieces. See the spring and how it's connected to the entire housing? This will push the entire silver cup down or up and opens up for more flow into the second chamber.

The secondary spring on the inside (within the 'cup') is probably another thermal spring that helps snap it shut to ensure no extra water flows into the other side of the dual hose housing. (I'm assuming here, it might just be an additional thermal spring to help open it even wider at hotter temps - first spring is 185F, internal spring is 210F, etc.)

That's the general principle of this type of thermostat and housing unit.

[macdude357]

Originally Posted by DukeofAlexandria

So this does actually open, and then expand WITHIN the housing unit.

If you take a look here...

https://www.turnermotorsport.com/f/p...SABEgK6hvD_BwE

You can get a better picture of what is going on. The upper ring (the largest ring in the housing) sits on the metal dual hose housing on top of the motor. The back 'cup' housing sits in the back. They are connected by the springs and that's it - two seperate pieces. See the spring and how it's connected to the entire housing? This will push the entire silver cup down or up and opens up for more flow into the second chamber.

The secondary spring on the inside (within the 'cup') is probably another thermal spring that helps snap it shut to ensure no extra water flows into the other side of the dual hose housing. (I'm assuming here, it might just be an additional thermal spring to help open it even wider at hotter temps - first spring is 185F, internal spring is 210F, etc.)

That's the general principle of this type of thermostat and housing unit.

I see. So the black ring seals off or opens up as the whole unit slides back and forth. That makes sense. Thanks!

[monterey]

Toss the old one in boiling water and see what it does.

[roastbeef]

tim, did you happen to put in a lower opening temp thermostat? i'm curious if you suspected it was failing or replaced it proactively...

there was some discussion in another thread, and this is basically the same thermostat with a slightly lower opening temperature.
oem is said to be 174F
and this one is 159F.
https://www.ecstuning.com/b-gates-pa...537836155~gat/

[macdude357]

Originally Posted by roastbeef

tim, did you happen to put in a lower opening temp thermostat? i'm curious if you suspected it was failing or replaced it proactively...

there was some discussion in another thread, and this is basically the same thermostat with a slightly lower opening temperature.
oem is said to be 174F
and this one is 159F.
https://www.ecstuning.com/b-gates-pa...537836155~gat/

I've been suffering engine temp warnings at the track for some time. I put in a CSF Radiator to see if that would help at all (it was free so I thought, what the heck). My last time out, I got water coming out of the overflow tank (I assume from getting too hot). I started to suspect that that something else might be the issue (weak water pump, partially stuck thermostat).

I did some testing where I started the car and let it warm up slowly. I used my laser pyrometer to check the actual temp of the radiator itself and found that it slowly increased about the same rate as the engine itself hitting over 100*F only a few minutes after starting the car, even though the oil temp was still pretty low. That told me that at the very least, my thermostat was not closing all the way so if that's the case, then it might be only partially opening. I also noticed that it takes a lot longer to get the oil temp up to 200 recently.

So, I went ahead and had it replaced and since they were in there, might as well replace the water pump since it had 90k miles on it. They also pressure tested the system and didn't find any issues. The pump had scoring on the impeller (so maybe it's got a bit of play and it not working to full capacity?). The thermostat seems to work when I put it in hot water but I don't know if it's fully opening/closing since I don't have a known good one to compare. Bottom line is that I re-did the test and the radiator stayed cooler than the engine for much longer than before. The car also warms up in about half the time. It will be 100F at Buttonwillow this weekend so that will be a good acid test to see if anything really changes at the track.

As for a lower temp unit, I figured at the track, the unit should always be open so it really wouldn't make a difference there.

[monterey]

I replaced my tstat when i got the occasional check engine light. When i took it out one side of the weld had broken off. The car still warmed up the same speed as the new one but somehow the sensor knew it was defective. The strange thing is I would get the check engine light before the engine was warm. Typically within 10 blocks of driving.

[maicol76]

Originally Posted by roastbeef

tim, did you happen to put in a lower opening temp thermostat? i'm curious if you suspected it was failing or replaced it proactively...

there was some discussion in another thread, and this is basically the same thermostat with a slightly lower opening temperature.
oem is said to be 174F
and this one is 159F.
https://www.ecstuning.com/b-gates-pa...537836155~gat/

This is not suitable for S65. need modification. I installed this after modification, then coolant temp average 7~10C and oil temp min. 5C lower with CSF radiator at the track.

[roastbeef]

Originally Posted by maicol76

This is not suitable for S65. need modification. I installed this after modification, then coolant temp average 7~10C and oil temp min. 5C lower with CSF radiator at the track.

Good info, thanks. The talk in the other thread made it sound like it was plug and play.

[drrust]

I just replaced my thermostat. The inside of the housing has a circular section that the thermostat rests in. So it looks like the upper section of the thermostat makes a partial seal in that section. If one pushes the spring on the thermostat the cup separates from the ring.