Lotus S2 Thermostat

[TEM]

My S2 has the Cosworth non-cross flow Kent engine and the swirl pot bolts directly to the engine (no hose from pot to engine).  There is no space for a thermostat.  is this normal or should I change my swirl pot?

[MV8]

The head opening where the water neck /swirl pot/filler attaches should have a thin step so the thermostat flange can sit flush. If the head does not have the step and the neck swirl filler does not have a step, then it wasn't equipped. The pot or head could be flycut or two cork gaskets used with the id opened up to clear the flange on one gasket.

 

If you have the heater valve open before warm up you might as well not bother with a stat. Stats do fail and can leave you on the side of the road when they stick closed.

[TEM]

Heater valve?  No heater in this car.

The S2 Owners Manual doesn't reference a thermostat and the pictures of the water fill pipe also don't look like they accommodate a thermostat.

[MV8]

No pics in this topic. Look at this 116e head. Lotus may not have used a stat, but Ford used a thermostat with these engines. Wear is greatest when the engine is cold from tighter clearances and an overly rich mixture falling out of suspension, trying to reach the combustion chamber, with the excess fuel washing down the cylinder walls.

[SENC]

I don't believe Lotus used a thermostat under the swirlpot on our Cosworth pre-crossflow engines.  A prior owner had one installed there, but it didn't seal right and leaked.  No problems since removing it.

[joe7]

According to what I've read, the problem with cooling is that without a blanking plate of some sort the water passes through the radiator to fast which doesn't allow it to cool. I fitted a thermostat to my 7 and drilled 3, 1/8 holes to allow the system to bleed. Problem is that the thermostat is too tall and interferes with the swirl pot. So I made a 3/8 aluminum inch spacer to get it to fit, with gaskets on either side As far as a thermostat failing and leaving one stranded on the side of the road. It isn't very difficult to resolve. Remove 2 bolt, remove failed thermostat reinstall 2 bolts.

[SENC]

15 minutes ago, joe7 said:

According to what I've read, the problem with cooling is that without a blanking plate of some sort the water passes through the radiator to fast which doesn't allow it to cool. I fitted a thermostat to my 7 and drilled 3, 1/8 holes to allow the system to bleed. Problem is that the thermostat is too tall and interferes with the swirl pot. So I made a 3/8 aluminum inch spacer to get it to fit, with gaskets on either side As far as a thermostat failing and leaving one stranded on the side of the road. It isn't very difficult to resolve. Remove 2 bolt, remove failed thermostat reinstall 2 bolts.

Not disagreeing, Joe, but wouldn't the pump determine the speed? 

 

I know there is a problem that it doesn't pump much at all when the engine is idling, thus the need to put a few revs in it from time to time to keep water flowing and the engine cooling.

 

I guess what you're describing could happen with continued high rpms where the pump is pushing water at maximum rate.  Putting a t-stat or blanking plate of some sort above the between the pump and the swirl pot would, I guess, put some back pressure on the pump and effectively slow it?

 

I don't race mine so not running long periods at 5k+ RPMs, but will say my Seven runs a much more consistent temp when on the highway at a consistent 4k+ rpm and I only approach issues when idling lengthy periods.  Turning on the fan and blipping the throttle periodically to get flow resolves on all but the hottest days.

Edited December 17, 2023 by SENC

[MV8]

3 hours ago, SENC said:

I don't believe Lotus used a thermostat under the swirlpot on our Cosworth pre-crossflow engines.  A prior owner had one installed there, but it didn't seal right and leaked.  No problems since removing it.

Sounds like the wrong thermostat was installed or the gasket was between the head and stat. The stat flange od should be 2.125", with 0.88" above the flange and 0.78" below. The flange should seat against the recess in the head. PN 13006 or 13356 should fit and open at 160f.

[MV8]

I've read that too, but coolant flowing at a greater rate will cycle more and improve cooling efficiency up to a point. The greater rate becomes an issue if it causes cavitation.

[SENC]

5 hours ago, MV8 said:

Sounds like the wrong thermostat was installed or the gasket was between the head and stat. The stat flange od should be 2.125", with 0.88" above the flange and 0.78" below. The flange should seat against the recess in the head. PN 13006 or 13356 should fit and open at 160f.

 

 

I think issue is that the swirlpot isn't designed for it.

 

Found a picture that may help. 

 

To overcome this design, the PO had bored out the base plate of the swirlpot to allow for a t-stat, which I suspect caused the sealing problems.

 

 

Edited December 17, 2023 by SENC

[SENC]

4 hours ago, MV8 said:

I've read that too, but coolant flowing at a greater rate will cycle more and improve cooling efficiency up to a point. The greater rate becomes an issue if it causes cavitation.

And perhaps this is the reason for the swirlpot.

[MV8]

1 hour ago, SENC said:

 

I think issue is that the swirlpot isn't designed for it.

 

Found a picture that may help. 

 

To overcome this design, the PO had bored out the base plate of the swirlpot to allow for a t-stat, which I suspect caused the sealing problems.

 

 

I see. The PO could have made a shim plate and two gaskets like Joe; probably 0.250 thick to avoid removing the pot locating lip. The plate holes would be precisely drilled and locate on the pot center lip so the stability would be maintained but obviously not made to fit both the pot and a stat.  

[jbcollier]

No thermostat in an S2/3 and you certainly can't easily fit one with pictured swirl pot.

 

Is there an issue?  Does it not warm up?  Or, take far too long to warm up?  No issue, no need to fit one.

 

I modified and fit a thermostat to my S3 crossflow because I regularly run in cool temps and want to some heat out of the heater.  I run a 160° thermostat (no extra holes) and it works great.