Ferret thermostats adjustable?

[Lynn Eades]

Malcolm, have you the space underneath to undo the screws on the side and slot the bellows frame down further. this would in theory at least give you a new start point.
I do think a new one is the answer though.

[LRDG]

That's a good idea, Lynn. I'll try that.

[Robin Craig]

Great information and suggestions all with great reasoning.

Thanks

R

[LRDG]

I unscrewed the 4 screws securing the bellows to the t/s body and elongated the screw holes. (They were already slotted so are part of the original setup by the OEM, I guess.) That got me a bit more flow area.

I did a calc of the final fully-open curtain flow area at the valve opening and it is now equivalent to the flow area of the port under the valve, so my anal engineering mind is now satisfied. Of course, the real test will be what temp she runs at.

[Lynn Eades]

Well done for having a go!.
The carriers have a radiator pressure cap that is adjusted then soldered, as is the oil cooler bypass valve.

[LRDG]

Since you raised the issue of rad pressure caps, I have some questions.

The pressure relief valve is a semi-permanent attachment to the top of the rad. Semi-permanent in the sense it is not just the standard screw-on cap. From the manuals, its setting is 10 psi.

The Ferret I am working on also has a "rad cap" on the filler opening in the line between the t/s outlet and the top of the rad, with a spring-loaded relief on it rated at 7 psi. I've tested this cap and it lifts at 6 psi.

So was the Ferret originally fitted with a non-relieving filler cap, leaving the rad-mounted relief valve to lift at 10 psi?

If I pressure test the whole system at 10 psi to check the system integrity and confirm the RV lifts, do I run the risk of finding it won't reseat, leaving me scrambling for a spare? It seems it has a soft rubber seat seal and who knows what condition it's in. (I think I know the answer to that question.)

I guess I run the risk of lifting the RV no matter what pressure I test at.

Is there a real risk of causing the pump shaft seal to leak in an unfixable way? It's a mechanical seal, and I know they can just let go if the rotor pops away from the stator and sticks open..

[45jim]

I replaced the bellows thermostat in my Ferret with one from a VW aircooled van (type II) and it worked perfectly. The only challenge was the threads are metric, in hindsight one from a Chevrolet Corvair would be a better choice in that regard, I believe the Corvair one is rated at 165F. Both are widely available from many sources. My Ferret had a solid non-venting rad cap.

When bellows style thermostats wear out, the opening stroke becomes inconsistent while the opening temperature may be correct. One time it opens fully and the next it only opens 70% for no apparent reason resulting in elevated temperatures. They are designed to fail in the open position but that means fully open at 150F while at ambient temperature they will not close completely. I think the VW one costs $40.