Question regarding looping rear coolant lines

[Temple90]

I have a 99 4runner in the northeast and the rear heater lines are rotting out.
I looked on the forum and saw that people are looping the lines at the firewall and bypassing the rear heater.
I would like to do the same, but was curious if I would loose a significant amount of coolant in the process. Should I drain the coolant prior to doing this?

Any feedback is appreciated.

 

[phattyduck]

If the truck is cold, you shouldn't lose much at all - it is at the top of the system. Make sure the cooling system has no pressure and it should be quick/painless. Loosen all the hoses first, then make the move quickly.

-Charlie

 

[brillo_76]

Not much coolant in that rear heater system. Always work on that with engine cold. You can loop the one hose right over to the other and clamp it off. If the heater lines are leaking it will drain itself very quickly. I had a picture on how my 97 is looped.

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[19963.4lsr5]

It’s one of the highest parts of the cooling system. Leave the rad cap on and just loop it.

That entire area is a neglected area. When I put the rebuilt engine in my 97 SR5 I replaced all those coolant hoses as well as the temp control valve. And the new hoses I bought were for our 4Runners that did not come with the rear heater. I still haven’t removed the rusty lines yet but it’s on my list.


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[JohnMc]

I got a set of 01-02 lines from a junkyard and spent about 30 minutes installing them. They're stainless, or aluminum. Whichever (can't recall), they don't have paint and they don't rust. Total coast - about $15.

 

[3bears]

as others have said, it is the high point in system, so not gonna loose much fluid. only thing I will add is that if you mess with the heater control valve...be gentle...they are brittle with age

 

[brillo_76]

I got a set of 01-02 lines from a junkyard and spent about 30 minutes installing them. They're stainless, or aluminum. Whichever (can't recall), they don't have paint and they don't rust. Total coast - about $15.

I believe the 01 -02 lines are stainless as I once said they were probably aluminium and got corrected . the connection brackets are steel though. I just wanted you to know.

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[Ser1clymb]

I'm going to toss in my 2 cents. I recently replaced the rear heater lines with new ones. I would suggest still burping the rad after you swap the hoses. You'll still get some air in the system no matter how quickly you swap them over. I felt that was some helpful advise from another forum member worth repeating.

 

[gamefreakgc]

Aww sad. I love the rear heater and I don't live in a very cold climate. In the winter I just leave it on all the time and it warms the cabin up nicely.

The lines are not that bad to replace like others have said if you ever want to come back and give it a fresh update. It's got a tiny heater core in the fan assembly that holds maybe a pint of coolant.

 

[brillo_76]

Anyone know exactly how much antifreeze is in that rear heater and lines ?? I mostly leave the radiator cap off when I change those lines and let it circulate a while. That way all the air gets pushed out. As the air has to work itself out.

Probably could run it a while with the radiator cap on. Then when the engine cools the entire way down. Open the cap and repeat that process a few times.

I cant see it being more then a few cups in the entire rear heater system. However, I never checked or measured it. Because when those lines rust through. You need to get that leaked stopped so you dont run out of antifreeze.


I only had one rust through on my 97 so far. I replaced the lines on Tetanus 1 as the PO just sealed it off.

I too enjoy the rear heater as it will heat up your seat when turned on. [ will work until I install seat warmers ]






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[nobb]

I would suggest cutting off the rusted section with a dremel, then get some 3/8" ID coolant hose and some clamps to bridge it back together. Then zip tie the hose to the frame to secure it, top up the coolant, and you're done.