Coolant system leaks. (1 Viewer)

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Question : If you have a leak at the heater control valve/hose connection point under the hood, would it be normal that this would leak when you have the heat on but not leak when you have it off ?


Background:

Due to a loose water pump belt I replace the belts and tensioned to spec (yes, using the right and expensive gauge). I drained all the stuff in the system and used a light (150/gal hour) pump to flush with distilled water. I then refilled everything with distilled water ONLY and burped it. Right now I am not putting coolant in as I want to find leaks now that the water pump is properly pushing liquid around.

There seems to be a slight leak around one of the oil cooler connections to pipes, but the bigger leak/spew is that at the heater control valve. I suspect I either leaked too much H20 to have it leak once I turned the heat off OR I don't understand enough about the system and it makes perfect sense that it wouldn't leak with the heater off. Which is it ?
 
So you flushed the system first and now are finding leaks? Could be that there was something there that was clogging and now is loose. If I remember correctly, water still get pushed to the valve but the valve blocks the water from entering the heater core so it can still leak at the valve if 1) the valve is faulty and failing, or 2) the hoses have hit a point where they are just leaking at their connection point to the valve and need to be replaced.
 
So you flushed the system first and now are finding leaks? Could be that there was something there that was clogging and now is loose. If I remember correctly, water still get pushed to the valve but the valve blocks the water from entering the heater core so it can still leak at the valve if 1) the valve is faulty and failing, or 2) the hoses have hit a point where they are just leaking at their connection point to the valve and need to be replaced.

Well I just took a second look at it. It is actually leaking at the hose that goes from the heater valve to the heater, not the other side of the valve. That hose I did not touch in doing the flush. It was the hose on the other side of the valve that I used to feed in distilled water to the heater(s) part of the coolant circuit.

I am beginning to agree with whomever said do NOT backflush.
 
It's leaking because it's distilled water now and before it was goopy coolant. But it still shouldn't leak with distilled water - though the cooling system shouldn't be filled with 100% distilled water either, even for troubleshooting. Distilled water is a solvent devoid of buffers and it's ph is too low. It's not doing the cast iron any favors that's for sure.

What may be happening (a guess) when the heater valve gets opened and then a leak develops, is 200° water now is flowing through the valve and the metal/rubber changes dimensions with the temperature change. When the valve is off, it's relatively cool. Just guessing.

Be very careful tightening the heater valve hose clamps. It's pipe nipples are soft brass and it's super easy too over tighten the hose clamps & crush the nipple.
 
It's leaking because it's distilled water now and before it was goopy coolant. But it still shouldn't leak with distilled water - though the cooling system shouldn't be filled with 100% distilled water either, even for troubleshooting. Distilled water is a solvent devoid of buffers and it's ph is too low. It's not doing the cast iron any favors that's for sure.

What may be happening (a guess) when the heater valve gets opened and then a leak develops, is 200° water now is flowing through the valve and the metal/rubber changes dimensions with the temperature change. When the valve is off, it's relatively cool. Just guessing.

Be very careful tightening the heater valve hose clamps. It's pipe nipples are soft brass and it's super easy too over tighten the hose clamps & crush the nipple.


OK thanks for the advice. I'm draining the water right now. I filled the truck with the 5+ bottles of Walmart distilled water last night, tested it and kept it in overnight since temps didn't go below 39 degrees last night.


While I let it drip out I'm goingto get the NAPA "valve to heater" hose that they have. It looks to me like the oil cooler to pipe hose should be a straight 5/8" hose (the hose that is on there is not straight, but I don't see why it cant be from the positioning.).


I wanted to refill with a cleaner/flush that I purchased - Valvoline Zerex - which is supposedly more effective than the Prestone flush. I want to put it in and drive around for 100 miles or 6 hours as the bottle suggests. The temps are supposed to go below freezing starting WEdnesday though and I don't know if the Zerex stuff can prevent freezing. Any suggestions ?
 
Try moving the clamp closer to the edge of the hose... I have had several pinholes appear on a couple pipes where the old clamps were. Replacing the hoses and positioning the clamps further out seems to have solved these issues. It took me forever to find the first one. The next two weren’t so mysterious... hth
 
Try moving the clamp closer to the edge of the hose... I have had several pinholes appear on a couple pipes where the old clamps were. Replacing the hoses and positioning the clamps further out seems to have solved these issues. It took me forever to find the first one. The next two weren’t so mysterious... hth

Shoot I wish I had tried this before I went to put a new hose on. Despite all the warnings, I managed to over-tighten and make the round heater core pipes ovular. I went ahead and got something on, but havent tested yet.

In filling up the rad with new coolant mix, a leak from the radiator petcock started. Now I am really screwed. Any advice on a fox to the petcock if I cant find a new Toyota one nearby ?

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It's just the oring. You can probably find another oring that should fit well enough at the hardware store.
 
It's leaking because it's distilled water now and before it was goopy coolant. But it still shouldn't leak with distilled water - though the cooling system shouldn't be filled with 100% distilled water either, even for troubleshooting. Distilled water is a solvent devoid of buffers and it's ph is too low. It's not doing the cast iron any favors that's for sure.

What may be happening (a guess) when the heater valve gets opened and then a leak develops, is 200° water now is flowing through the valve and the metal/rubber changes dimensions with the temperature change. When the valve is off, it's relatively cool. Just guessing.

Be very careful tightening the heater valve hose clamps. It's pipe nipples are soft brass and it's super easy too over tighten the hose clamps & crush the nipple.


This is turning into a Road Runner Cartoon where the Coyote puts his hand against a leak in a wall only to have a leak develop elsewhere.

It seems that the brass is bent (as OSS forewarned) on both heater core pipes that are coming out of the firewall and leaks are at both. I have installed new hoses and clamps at both, using the banded generic clamps from Napa as opposed to the OEM ones.

I replaced the valve to heater hose (and yes, the brass is bent into a non-circular shape either because I just did it or it was that way from before), started filling with coolant mix and that started leaking at the other heater core pipe to coolant pipe hose connection (always at the heater core connection). This leak occurred without even starting the engine, just the initial fillup (I stopped filling up once the leak started).
 
This is turning into a Road Runner Cartoon where the Coyote puts his hand against a leak in a wall only to have a leak develop elsewhere.

It seems that the brass is bent (as OSS forewarned) on both heater core pipes that are coming out of the firewall and leaks are at both. I have installed new hoses and clamps at both, using the banded generic clamps from Napa as opposed to the OEM ones.

I replaced the valve to heater hose (and yes, the brass is bent into a non-circular shape either because I just did it or it was that way from before), started filling with coolant mix and that started leaking at the other heater core pipe to coolant pipe hose connection (always at the heater core connection). This leak occurred without even starting the engine, just the initial fillup (I stopped filling up once the leak started).
You can reform those pipes. I normally use a pair of needlenose and gently bend and form them back to round.
 
You can reform those pipes. I normally use a pair of needlenose and gently bend and form them back to round.

How close to round can you get ?

This thing is becoming disasterous. Coolant leaked at all the heater hosed at the firewall AND interior to the cabin. I cant tell if coolant was simply getting inside the cabin from the external hose unroundedness mess or what.

Before I go the route of a new heater core, I am going to remove the valve and all hoses from the heater junction at the firewall. I will try to re-round the pipes, then re-assemble bottom up.

If this still doesnt work, then heater core time after all.
 
Well there is a large grommet at the firewall that should NOT allow water inside the cabin so if you are getting a leak inside I am afraid you may have a bigger issue with your heater core.. Heater Core is NLA so your best bet is going to be to get it repaired if it is a problem.
 
Well there is a large grommet at the firewall that should NOT allow water inside the cabin so if you are getting a leak inside I am afraid you may have a bigger issue with your heater core.. Heater Core is NLA so your best bet is going to be to get it repaired if it is a problem.


Yeah I was afraid of that logical reality. The grommet is there and is about 5 years old (I did some heater core work when I first got it in 2011).

A local plumbing supply has an old 4-piece swaging tool set - apparently the thing to use to straighten bent copper and brass tubes - that I am going to get for $20 and give a try before the heater core route.

Any idea what the inner diameter of the brass pipes should be ?


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@OSS @CaptClose One of these two should know. Also, from my understanding the brass pipes are not actually connected directly to the heater core, rather pressed in with rubber o-rings. When those o-rings fail all kinds of fun happens. This may also be your issue if you are getting water inside the cab.
 

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