I'm creating this post as an alternative to the 620 Cooling thread which now focuses on remedial work being used to correct the overcooling issue affecting the 620.
I would treat this solution and thread cautiously, I'm not sure what I'm doing. I don't have the experience or technical knowledge shown by the amazing team in the other thread. Though I do actively invite input, and critique to help optimize the concept I'm using.
To be clear I'm doing this as I don't have the confidence to remove the intake manifold with all the extra ancillaries it has on the 620 due to the supercharger. This confidence may change over time, and I may fit the solution that the team have come up with. I'll probably purchase the parts and leave them on my workbench attempting to find the bottle *irked*. For the time being, I'm going to try an easier approach and compare the results.
The approach I'm using is to install a coolant bypass in front of the hot side of the radiator, diverting coolant sub 89c from the radiator back to the thermostat housing. Coolant over 89 will be sent to the radiator and then back as normal.
To do this, I'm cutting into the hot side top coolant hose between the engine and radiator, into which I will install a bypass thermostat housing. I will also cut into the bottom radiator return hose and install a T-piece. The T-piece will receive the bypass coolant from the bypass thermostat housing. Coolant under 90 should flow through this loop back to the OEM thermostat housing.
The team in the other thread have confirmed and also acknowledged by Caterham Cars part of the overcooling issue is due to coolant pressure forcing the thermostat in the OEM housing open. Nullifying its presence, ie it appears stuck open. I'm therefore going to leave the OEM thermostat in place. The thermostat used in the OEM housing receives the pressure at the rear of its surface, hence reacting the way it does. The bypass housing is a T junction, my hope is that the pressure will behave differently in the housing and won't force the thermostat into a set position. This might be a failure point in the design. Only time will tell.
My parts list are as follows, all purchased from carbuildersolutions.
|By-Pass Thermostat 87 Degree||SKU: BYST87||£32.40||1||£32.40|
|Gates Green Stripe Flexible Hose 32mm 5ft Long||SKU: GRE32||£69.60||2||£139.20|
|Stainless Steel Hose Clip 30-40mm||SKU: H30SS||£2.16||7||£15.12|
|Hose & Pipe Cutter||SKU: HOSEC||£7.80||1||£7.80|
|32mm Welded Aluminium Tee||SKU: TEE3232||£24.00||1||£24.00|
Link to the bypass https://www.carbuilder.com/uk/by-pass-thermostat-87-degree
You might notice I've opted for flexible coolant hoses. I'm not sure what these are like. I'm using them as I expect to connect the middle port of the bypass thermostat to the hot rail, and then attach the housing to the cruciform. As both output ports from the bypass housing are at 90 degree I'll need to ensure I have the flexibility to route the coolant hose around the intercooler. This might be overthinking things, but I'm trying to predict unforeseen issues. I think I'll also source some standard silicon hoses in case they fit as I'd prefer them. Connecting the bypass loop to the bottom T should be simple, but I will need to cut and reuse the factory hose.
I think that covers it, I'd love to know your thoughts.