[SOLVED] Water swirl pot

[GulfSeven]

I'm having an issue where the coolant is rising to the top of the expansion bottle on track. It's been suggested to me that it's a common fault with the 270 and 310 because they don't have the radiator bleed hose to the expansion tank that was fitted to the earlier Sigma-engined cars.

Has anyone fitted a water swirl pot to solve the same problem? Do people fit these to Caterham race cars?

[7 wonders of the world]

Duratec's dont run a rad bleed either - the problem is a variation with expansion bottle manufacturers with some having a slightly larger borer (some been sleeved) in the bleed pipe which allows too much water to be pushed into the bottle which displaces the air which then finds a new home in the rad.

You can restrict the bleed flow into the bottle by simply inserting a roll pin into the bottle pipe use the one with the tightest fit, leave a small amount proud in case you eve need to remove it.

My first bottle was perfect, replacement needed this tweak - no other changes to the system at all, now normal service has been resumed.

[GulfSeven]

I've also had it suggested that the system sucks air out of the expansion bottle under heavy braking on track, which is why I was asking about swirl pots. Do you have any more details on the roll pin fix?

[7 wonders of the world]

Hi Tim,

insert the roll pin into the bottle itself, I have a small box of pins and selected one that just tapped into the plastic neck, this reduces the ID yet offer a sensible bleed flow without filling the bottle.

[GulfSeven]

So is this insert standard on some cars?

[ECR]

I have a swirl pot fitted to my VX 2.0. With the original pancake header fitted above the front crucifix the engine would be covered with water spray after a hard session on track. It's perfectly dry now. It's fitted in the top rad hose and just fits under the nosecone

[GulfSeven]

Okay, so I can confirm that my car does not have a restrictor in the expansion tank return pipe.

[GulfSeven]

Double post.

 

[Dixa1225]

I have just check my 2020 academy car. No restrictor in the tank. Not had any issues you are having on track.

[GulfSeven]

I think I'll ask Caterham themselves for an opinion before I proceed with anything...

[GulfSeven]

Caterham and Williams have both independently advised against modifying the cooling system and have suggested it could be an air lock or possibly another faulty expansion bottle cap. So I'm going to get the system bled and fit another cap before my next track day in July.

[ScottR400D]

All these threads about sigmas' issues with oil catch tanks and cooling systems makes me glad I got a Duratec!

On a serious note has something changed in recent years? There must be thousands of Sigma engined 7s out there and it seems to be just recently that these things are occurring? 

 

[GulfSeven]

To round off this thread...

The issue remained after bleeding the system and fitting another cap, and was subsequently diagnosed as an intermittent seal between the cap and the expansion bottle. Williams did a pressure test and a sniffer test to rule out any other problems, then changed the expansion bottle under warranty. It's been fine on the road for the last month and also at today's trackday.

So no need to modify the system