FJZ Thermostat Leak (1 Viewer)

Joined
Jan 30, 2021
Messages
10
Location
Tampa, FL
Hey there,

I recently did a whole bunch of cooling maintenance on my '94 JDM 80, to include the PHH, water pump, heater hose lines, etc. Included in that was a new thermostat. The initial reason for me opening all of this up was because I had a small leak from a heater hose on the T-fitting. That has been addressed.

Since replacing the thermostat, I seem to have a worse leak than the heater hose I had before. When idling, it's fine, but under throttle there is a fair bit of coolant surging from the top of the thermostat, specifically where housing bolts to the block. I torqued it to spec and took forever to get the thermostat and new o-ring in place. This may sound dumb, but I'm hoping it'll seal itself with a few heat cycles. If not I'll have to pull it back apart.

Does anyone have any experience with this issue? Maybe use some RTV on the thermostat housing? Thanks in advance.
 

Irish Reiver

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Joined
Oct 24, 2015
Messages
1,613
Location
Orlando, Florida
Where exactly is it leaking from? There 3 or 4 potential hoses in that area. Is it coming from the hard line that holds the thermosat or possibly the gasket between the thermosat housing and the block? There is also the 3 o rings in the same vicinity that can let go if not replaced.
 
Joined
Jan 30, 2021
Messages
10
Location
Tampa, FL
Good question. It's leaking from the arrow in the picture. From what I can tell, it's seeping up from there and then pooling where I circled. It doesn't seem to actually be leaking from the circle despite how it looks. I replaced all of the o-rings in that vicinity with new OEM Toyota o-rings.

I will say, it took me forever to get the thermostat/gasket to stay in place when trying to bolt the housing back on, but it seemed good when I put it back together.

IMG_2003.jpg
 
Joined
Feb 16, 2012
Messages
201
Did you replace with all new seals and gaskets? Hard to tell what gasket or seal is leaking since we can’t see it. I would get all new seals\gaskets break it down again and replace them all in that area and torque to spec. Should be good after.
 
Joined
Jan 30, 2021
Messages
10
Location
Tampa, FL
Did you replace with all new seals and gaskets? Hard to tell what gasket or seal is leaking since we can’t see it. I would get all new seals\gaskets break it down again and replace them all in that area and torque to spec. Should be good after.
I did. Swapped in all new OEM Toyota seals-o-rings when I changed everything over. That's the frustrating part; it doesn't make sense as to why it's still leaking. I was considering tearing it down and using RTV on the thermostat hosing just to be sure..
 
Joined
Feb 16, 2012
Messages
201
I did. Swapped in all new OEM Toyota seals-o-rings when I changed everything over. That's the frustrating part; it doesn't make sense as to why it's still leaking. I was considering tearing it down and using RTV on the thermostat hosing just to be sure..

That’s really odd. My only other thought is one of the parts is damaged and is not sealing properly. I would avoid the RTV unless you find a spot that’s damaged.
 

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