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As far as I know, the best block-off seems to be the actual sensor (even if it's not actually in use as a "sensor", i.e. not plugged into the wiring harness). I'm shocked that the sensor isn't working in this role. Isn't there an O-ring on the tip? If so, maybe it was an inferior batch of O-rings from that supplier causing each one to leak. I've had similar troubles in the past with dipstick tube O-rings from various brands at various times.
Maybe a different brand (or if you can just find an O-ring of the correct size separately) would work.
I just ordered an o-ring kit. If that doesn't work I also found every size coolat block off caps that will work. But its nice to keep the level sensor working.
just a thought, is the port clean and free of debris or scratches? is it cracked at all?
Just removed the sensor. Port is perfect inside.
But look at the 2nd o-ring. It explains why this o-ring is leaking even though the first o-ring should stop it from leaking especially fully cold under zero pressure.
But the other two sensors also leaked. No way I tweaked all three 2nd o-rings while popping them in. I’ve been R&Ring these sensors for 25 years with zero issues.
Im gonna see if this o-ring kit provides slightly fatter o-rings to put on. If not I’ll cap it off.
About 10-12 years ago, I had a huge problem getting the dipstick tube (it's the old O-ring style) for my TH350 to stop leaking. I tried several "automotive" O-rings of the proper size, and none of them would stop the leak (they were all from Dorman, sold from various places). I was just about ready to convert to the "top hat" style dipstick seal when I decided to try a completely different non-automotive supplier sold by my local Ace Hardware stores. I saved a picture of the difference between the two, it's obvious why the Dorman one would never seal. Keep in mind, these two O-rings are listed as being *exactly* the same size (in every dimension), but the Ace one is clearly more robust. I did this a decade ago, and the Ace one has never leaked:
I ordered the o-ring kit from your post above, good idea to try other o-rings.
I'm hoping exactly that, that I can find an o-ring thats just a little fatter.
Originally Posted by RPM WS6
About 10-12 years ago, I had a huge problem getting the dipstick tube (it's the old O-ring style) for my TH350 to stop leaking. I tried several "automotive" O-rings of the proper size, and none of them would stop the leak (they were all from Dorman, sold from various places). I was just about ready to convert to the "top hat" style dipstick seal when I decided to try a completely different non-automotive supplier sold by my local Ace Hardware stores. I saved a picture of the difference between the two, it's obvious why the Dorman one would never seal. Keep in mind, these two O-rings are listed as being *exactly* the same size (in every dimension), but the Ace one is clearly more robust. I did this a decade ago, and the Ace one has never leaked:
We have seen this before. Check the bung that your sensor goes into and make sure it isn't bent or damaged. I think the bunched-up O-Ring is your problem.
The sensor should go in smoothly with a slight twist. If there is a foreign object or dent in the bung, that ring won't seal.
A larger O-Ring will likely make your problem worse.
We have seen this before. Check the bung that your sensor goes into and make sure it isn't bent or damaged. I think the bunched-up O-Ring is your problem.
The sensor should go in smoothly with a slight twist. If there is a foreign object or dent in the bung, that ring won't seal.
A larger O-Ring will likely make your problem worse.
Then all you need to do is seat that O Ring so it doesn't bunch up un the bung. Slightly twisting the sensor as you press it in is usually enough. You can also use a verry little bit of Super Lube on the rings: https://www.super-lube.com/o-ring-silicone-grease
(If you don't already have Super Lube, you should. It's the best lube for the door hinges and is called for on some other parts. I really like their pen applicator.)
Maybe. Drive about an hour. Pulled it into my garage up on the front tire ramps. Went inside and waited about 15-20 minutes for the heat and pressure to build up a little.
Not leaking.
I’ll check it every day fur a week and call it good.
06-19-2024, 04:53 PM
Radiator coolant level sensor “port”…..leaking 
