fjz80 Coolant leak around bypass pipe

Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Hello everyone,

Looking for some advice. I redid my cooling system and I've been chasing a intermittent leak near the bypass pipe. I replace the bypass #1 the first time, but didnt use any rubber grease so the theory was that the o-ring because dislodged. I took it apart, lubed, put it back together easily. It still leaked, but intermittently. At first it leaked for a day, then went away for 2. Then it leaked a little. Then once it leaked a lot for just running about a minute.

So I assumed the bypass pipe had a hairline crack, so I replaced it, new o-rings, lighter on the grease this time. I also replaced the thermostat housing gasket and heater pipe gasket. Everything is torqued to 15 ft lb. So I bleed the system, no leak. I let it cap it - let it idle and drive in the neighborhood. No leak. I do a quick errand and she leaked a little over the course of 3 miles (round trip). I use compressed air to dry the area, start the truck and cannot see any leak. I let it idle and I rev it, and iddle, and rev and after 10 minutes...nothing. So I drive it, thinking I'm not working the system hard enough. I check it several times. Nothing. I've never heard of a leak that goes away. Is it maybe needing the burn the toyota rubber grease off to seal effectively? Very open to suggestions here.

EDIT: I finally got a glimpse of where the leak is coming from, coolant came from inside the bypass pipe - where bypass #1 is located. I've already replaced the o-rings there twice, and the new bypass tube #1, and the bypass pipe. The inside of the thermostat housing doesnt look pitted, but Im going to take it apart for the third time and see what I can discover. I will say, I thought the bypass #1 went into the housings too easily.

New bypass pipe 1635166010
New water bypass #1 1626866010
New o-rings (3) 9030129006
New thermostat
New thermostat housing gasket1611966020
New gasket for heater tube1578566010

bypass pipe.jpg
 
Last edited:
Joined
Dec 10, 2007
Messages
8,638
Can you determine exactly where the leak is coming from??

One method: clean the area completely off, take a few close up photos, cold engine, run the engine a few minutes, shut it down, take a few photos.
If no leaks, run the engine longer, shut it down, take photos.

Start again with a hot engine, clean it off, take a few photos, wait for the engine to cool down, or while it cools down say every 15 minutes, take a few photos (close up).

Put all the photos on your computer, magnify and study them closely looking
for where the leak actually starts from.

Or, go out and buy/rent/borrow a cooling system pressure test kit and some dye.



There are at least 4-5 possible sources in that area.

Did you find any pitting or erosions on the mating surfaces of the Thermostat plate (housing)?


BTW: are you using a new OEM radiator cap?

Note: replaced Scotty's video with something easier on the ears.
Either way, dye and/or pressure test. Some parts stores will "rent"
a pressure tester.
 
Last edited:
Joined
Nov 9, 2012
Messages
12,874
Location
Olathe, KS, USA
Hello everyone,

Looking for some advice. I redid my cooling system and I've been chasing a intermittent leak near the bypass pipe. I replace the bypass #1 the first time, but didnt use any rubber grease so the theory was that the o-ring because dislodged. I took it apart, lubed, put it back together easily. It still leaked, but intermittently. At first it leaked for a day, then went away for 2. Then it leaked a little. Then once it leaked a lot for just running about a minute.

So I assumed the bypass pipe had a hairline crack, so I replaced it, new o-rings, lighter on the grease this time. I also replaced the thermostat housing gasket and heater pipe gasket. Everything is torqued to 15 ft lb. So I bleed the system, no leak. I let it cap it - let it idle and drive in the neighborhood. No leak. I do a quick errand and she leaked a little over the course of 3 miles (round trip). I use compressed air to dry the area, start the truck and cannot see any leak. I let it idle and I rev it, and iddle, and rev and after 10 minutes...nothing. So I drive it, thinking I'm not working the system hard enough. I check it several times. Nothing. I've never heard of a leak that goes away. Is it maybe needing the burn the toyota rubber grease off to seal effectively? Very open to suggestions here.

New bypass pipe
1635166010

New water bypass #1
1626866010

New o-rings (3)
9030129006

New thermostat

New thermostat housing gasket
1611966020

New gasket for heater tube
1578566010

View attachment 3077572
Did you replace the little pipe with the two O-rings on it? How snug does it fit inside the new bypass pipe?

How are you installing the O-RIngs? Sometimes, depending on HOW you install them you could be cutting them when you roll them over the sharp edges or stretching them or using a screwdriver to pull them over. (I've seen all kinds of stuff)

Make sure your are using Toyota O-Rings.
Slip them on dry. they should sort of "roll" over the end and drop into the groove. Massage the O-Ring as in work it linear around the piece of pipe with your fingers to get it to "relax" so there are no twists in the O-ring.
I use fresh anti-freeze to coat mine before I install so there is no grease or contamination or any other substance in there.
Are you sure you didn't wedge the short pipe in the hole when assembling? I didn't like how it felt trying to install it with the short pipe already in the bypass pipe, so I inserted the short pipe first, then installed the bypass pipe over top and slid straight down into position for the bolts.
I used Scotch-brite to clean all surfaces and sealing surface to remove all gummed up antifreeze and any residue in there. If someone poked a screwdriver around in there to clean out the gunk, they may have scratched the sealing surface of the wall and junked the aluminum part that is that housing.
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Did you replace the little pipe with the two O-rings on it? How snug does it fit inside the new bypass pipe?

How are you installing the O-RIngs? Sometimes, depending on HOW you install them you could be cutting them when you roll them over the sharp edges or stretching them or using a screwdriver to pull them over. (I've seen all kinds of stuff)

Make sure your are using Toyota O-Rings.
Slip them on dry. they should sort of "roll" over the end and drop into the groove. Massage the O-Ring as in work it linear around the piece of pipe with your fingers to get it to "relax" so there are no twists in the O-ring.
I use fresh anti-freeze to coat mine before I install so there is no grease or contamination or any other substance in there.
Are you sure you didn't wedge the short pipe in the hole when assembling? I didn't like how it felt trying to install it with the short pipe already in the bypass pipe, so I inserted the short pipe first, then installed the bypass pipe over top and slid straight down into position for the bolts.
I used Scotch-brite to clean all surfaces and sealing surface to remove all gummed up antifreeze and any residue in there. If someone poked a screwdriver around in there to clean out the gunk, they may have scratched the sealing surface of the wall and junked the aluminum part that is that housing.

All oem, new pipe and o-rings. The o-rings seem to fit good. It took very little pressure to put the new bypass pipe #1 into either the new bypass pipe or the thermostat housing. I have done it both ways
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Can you determine exactly where the leak is coming from??

One method: clean the area completely off, take a few close up photos, cold engine, run the engine a few minutes, shut it down, take a few photos.
If no leaks, run the engine longer, shut it down, take photos.

Start again with a hot engine, clean it off, take a few photos, wait for the engine to cool down, or while it cools down say every 15 minutes, take a few photos (close up).

Put all the photos on your computer, magnify and study them closely looking
for where the leak actually starts from.

Or, go out and buy/rent/borrow a cooling system pressure test kit and some dye.



There are at least 4-5 possible sources in that area.

Did you find any pitting or erosions on the mating surfaces of the Thermostat plate (housing)?


BTW: are you using a new OEM radiator cap?


Ive watched and tried, i cannot tell where its coming from. I am gonna keep trying.

I am using a gates radiator cap, new. Its the only non oem part, as i like their relief valve
 
Joined
Feb 12, 2021
Messages
158
Location
New Idria 95043
Can you determine exactly where the leak is coming from??

One method: clean the area completely off, take a few close up photos, cold engine, run the engine a few minutes, shut it down, take a few photos.
If no leaks, run the engine longer, shut it down, take photos.

Start again with a hot engine, clean it off, take a few photos, wait for the engine to cool down, or while it cools down say every 15 minutes, take a few photos (close up).

Put all the photos on your computer, magnify and study them closely looking
for where the leak actually starts from.

Or, go out and buy/rent/borrow a cooling system pressure test kit and some dye.



There are at least 4-5 possible sources in that area.

Did you find any pitting or erosions on the mating surfaces of the Thermostat plate (housing)?


BTW: are you using a new OEM radiator cap?

Once you hear his voice you never forget it...
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Can you determine exactly where the leak is coming from??

One method: clean the area completely off, take a few close up photos, cold engine, run the engine a few minutes, shut it down, take a few photos.
If no leaks, run the engine longer, shut it down, take photos.

Start again with a hot engine, clean it off, take a few photos, wait for the engine to cool down, or while it cools down say every 15 minutes, take a few photos (close up).

Put all the photos on your computer, magnify and study them closely looking
for where the leak actually starts from.

Or, go out and buy/rent/borrow a cooling system pressure test kit and some dye.



There are at least 4-5 possible sources in that area.

Did you find any pitting or erosions on the mating surfaces of the Thermostat plate (housing)?


BTW: are you using a new OEM radiator cap?

Just say your other questions, sorry.

No pitting, i clean it up pretty good.
 
Joined
Dec 10, 2007
Messages
8,638
One of my 80's came with an aftermarket cap that seemed to work, but I had a small hose leak. Replaced the cap with OEM, leak went away but eventually I had to replace that hose. Point is, the aftermarket cap was overpressurizing the system which revealed a weak link.

I'd replace the cap with the correct OEM part. MIght not be the cause of your issue, but won't hurt.
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
One of my 80's came with an aftermarket cap that seemed to work, but I had a small hose leak. Replaced the cap with OEM, leak went away but eventually I had to replace that hose. Point is, the aftermarket cap was overpressurizing the system which revealed a weak link.

I'd replace the cap with the correct OEM part. MIght not be the cause of your issue, but won't hurt.
Will do. Just ordered it at my local dealer
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
One of my 80's came with an aftermarket cap that seemed to work, but I had a small hose leak. Replaced the cap with OEM, leak went away but eventually I had to replace that hose. Point is, the aftermarket cap was overpressurizing the system which revealed a weak link.

I'd replace the cap with the correct OEM part. MIght not be the cause of your issue, but won't hurt.
Put my old cap back on, same result. Dang, i was hoping
 
Joined
Dec 10, 2007
Messages
8,638
FWIW I replaced the Scotty Kill-your-ears video in post #2 above with another
that's more pleasing (to the ear). ;)
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Just made an edit:
I finally got a glimpse of where the leak is coming from, coolant came from inside the bypass pipe - where bypass #1 is located. I've already replaced the o-rings there twice, and the new bypass tube #1, and the bypass pipe. The inside of the thermostat housing doesnt look pitted, but Im going to take it apart for the third time and see what I can discover. I will say, I thought the bypass #1 went into the housings too easily.
 
Joined
Nov 5, 2021
Messages
22
Location
Jacksonville FL
Found the culprit.

Hairline crack in the metal where the bypass #1 goes. I will need to see what is involved in replacing that, but it looks like a lot.

810A1644-FF0C-44E3-9239-04B58D408CEF.jpeg
 
Joined
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Messages
12,874
Location
Olathe, KS, USA
Found the culprit.

Hairline crack in the metal where the bypass #1 goes. I will need to see what is involved in replacing that, but it looks like a lot.

View attachment 3078132
Damn!

I think that's part of the timing cover casting!

Maybe it's time to do a head gasket as PM, replace your timing chain and slippers and all the other stuff on the front.

Maybe to "get by" you could clean it well, smear some epoxy in there and on the outside in order to seal it and hold it while you gather parts and supplies. You would have to make it very smooth.
 
Joined
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Messages
22
Location
Jacksonville FL
Damn!

I think that's part of the timing cover casting!

Maybe it's time to do a head gasket as PM, replace your timing chain and slippers and all the other stuff on the front.

Maybe to "get by" you could clean it well, smear some epoxy in there and on the outside in order to seal it and hold it while you gather parts and supplies. You would have to make it very smooth.
That is my theory, too. I cannot find a part number so far, and I tried for about 45 minutes. I can find a picture of it, but no part number. Which is concerning...
 
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Location
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I just saw that Rockauto has an Aisin oil pump/timing cover available for about 240 bucks. Not sure how much the part is from Toyota.
52E86F17-7B4B-4B29-9F52-FD5F6A440076.png
 

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