3FE Coolant Leak at Thermostat Housing (1 Viewer)

[ocinataS]

After doing a coolant flush and doing some light wheeling this weekend, I noticed a little bit of coolant splattered above the thermostat. Looks like it’s coming out the part with the black cap and two small hoses. The FSM doesn’t identify This part, but it has two slits on the cap and it looks like the coolant is coming out the bottom slit. Any ideas on why this would leak? Is it a vent or some kind?

 

[jonheld]

BVSV valve.
Part# 25820-13020

 

[paulzak]

Plastic is getting pretty brittle on my '92 FJ80. I approach every job gingerly now to avoid broken plastic. My recollection is that it's hard to totally avoid flexing stuff when removing the thermostat housing even after disconnecting the sensors.

 

[ocinataS]

BVSV valve.
Part# 25820-13020

Thanks Jonheld. You think it’s due a replacement BVSV? Not sure what the internals look like/what could be broken. I read here they can be difficult to remove.

 

[jonheld]

Remove the top of the housing like you did when you replaced the thermostat. You can put it in a bench vise to remove the valve.
However, I would make certain that the valve is actually leaking and not getting sprayed from one of the other hoses.

 

[ocinataS]

Remove the top of the housing like you did when you replaced the thermostat. You can put it in a bench vise to remove the valve.
However, I would make certain that the valve is actually leaking and not getting sprayed from one of the other hoses.

I tightened the hoses around there and I’ll watch it for a while to make sure it’s the valve. But looks like coolant’s getting blown backward from that slit by the radiator fan. It’s a very slow leak... haven’t lost much.

 

[jonheld]

Any coolant loss is too much. The system needs to hold pressure in order to operate properly.

 

[ocinataS]

Any coolant loss is too much. The system needs to hold pressure in order to operate properly.

@jonheld do you know the part number for the lower hose coming off the upper thermostat housing? I might as well replace that while I’m at it.

 

[jonheld]

@jonheld do you know the part number for the lower hose coming off the upper thermostat housing? I might as well replace that while I’m at it.

Use partsouq.com to look up part numbers. Enter your VIN and you get everything on the truck.