bypassing rear heater hoses?

[Brian894X4]

So, I'm doing a PM of all heater hoses. Basically I want to do this once and forget about it for many years to come. Problem is, I can't replace every single heater hose. There's at least one formed hose that Toyota doesn't sell seperately. It's the passenger side rear heater hose and goes from the T down to another pipe behind the engine and into the firewall via another hose. There's a second pipe in the loop on the driver's side I think. And there's two lower firewall (if I'm looking at the diagram right) hoses that look impossible to get too. Maybe these aren't firewall, but just connector hoses to the rear metal heater pipes.

So, I don't live in a rust area. There's no rust on the truck, so my rear heater pipes are probably OK, but I'll check later tonight just to be sure. Thing is, I almost never use the rear heater (only one seat left back there anyway) and I'm wondering if I shouldn't just bypass it all together to avoid any potential issues down the road.

One could just run a heater hose from the passenger side T to the driver's side and bypass it that way. I'm thinking I'd rather just replace the passenger side T with a straight fitting, and cap off the heater hose on that side. I haven't looked at the driver's side, but I think there's another T fitting there that can just be replaced with a straight fitting and then just cap off the heater hose. That way it can be retrofitted easy enough, with everything left in place, but no risk of a rear heater system failure stranding the vehicle.

I haven't decided if I want to do this, but since having rear heat is such a low priority it would really suck to have some part of the rear heater system fail in the middle of the desert somewhere.

Anyone else tried this? And if so, what method did you use to bypass?

 

[Doc]

My motto is "if it ain't broke..."

Anyway- if it's fine, leave it alone. Carry some spare hose with you in your spares box when you travel. Under the same train of thought you should bypass your power steering too, cause it could leak and fail.

 

[sundaypunch]

PM is good but I think you are worrying too much. If you keep your cooling system flushed and live in a rust-free area the odds of those rear heater hoses giving you a problem are next to zero.

 

[elhombre]

I bypassed mine because I wanted to change all the hoses out with 150k miles on the old ones. The rear heater hoses also travel right over you cats. It seemed to me that I could eliminate potential failures by cutting them out of the system. I went to NAPA and they sell heater hose pieces that have a 90 degree turn in them which is what you need to get it done. It was a pain to get my hands back there to get it done, but not impossible. I even took my heater out from under the seat and am waiting for it to get cold again so I can sell the whole setup in the used parts section.

 

[Brian894X4]

The only reason I think about it, is that I know that certain firewall hoses and the PHH fail at about the age and mileage my rig is, so if those can fail, why not the rest of the hoses? The entire coolent system is only as good as the weakest hose, including the rear heater hoses.

I don't some fairly remote driving, so ultimate reliability is very important to me. And I'm tearing into much of the cooling system anyway this weekend.

I know the PHH is close to an EGR related exhaust pipe, so it's subject to excess heat, which is why some say it fails so commonly. The rear heater pipes and hoses run right above the main exhaust manifold, then run over the exhaust and above the cats.

I haven't decided if I still want to or not, it depends on the condition of the lines above the cat. If they are showing signs of possible failure, it will definately be bypassed, but if it looks good as new, maybe not. What I might is rig up a spare bypass tube the correct length, throw it in my spares box and then I'll be ready to bypass the rear heater system if ever needed with minimal fuss.

 

[Brian894X4]

I bypassed mine because I wanted to change all the hoses out with 150k miles on the old ones. The rear heater hoses also travel right over you cats. It seemed to me that I could eliminate potential failures by cutting them out of the system. I went to NAPA and they sell heater hose pieces that have a 90 degree turn in them which is what you need to get it done. It was a pain to get my hands back there to get it done, but not impossible. I even took my heater out from under the seat and am waiting for it to get cold again so I can sell the whole setup in the used parts section.

Thanks for the tip on Napa and the 90 degree hoses. That will help me out whether I bypass or not. I need a 90 degree hose that Toyota does not sell.

How did you bypass in your set up? Looking at the heater hose diagram, seems there is two ways to bypass.

One is to keep all the fittings and run a bypass hose from the passenger side firewall T-fitting to the driver's side T-fitting. Or, one could possibly eliminate the T-fittings all together, and make the heater hose system much simplier....

If one replaced the passenger side T fitting with a straight fitting, that would eliminate that side. Then for the driver's side, from the bottom of the U shaped pipe on the firewall, run a single hose directly into the firewall. Although it looks like the pipe one would be bypassing that way, might feed the firewall in two places, plus the rear heater hose, which would make that idea a little more complicated.

 

[nuclearlemon]

i haven't done it yet, but i will be eliminating the rear heater circuit. my hard lines are beyond crap...they look worse than the underside of a ship that's been in the water the last four decades. originally, i was going to get some from a junker, but after talking to gary waggoner, i came to the decision to just eliminate them. the cruiser has no problem getting plenty warm in the winter and i never have passengers.

 

[Aharon]

There is a hose that toyota sells that will work for both rear heater hoses. It is for a previous model landcruiser. You cut it in half and then use one half for the passenger side rear heater connection and the other half for the driver side rear heater connection. The only way to get the exact hoses from Toyota is to order the rear heater hard lines that run down the transmission tunnel. The rear heater hoses are a different diameter from the rest, they are 14mm vs 16mm for all the others.

Hopefully CDan will chime in here as I recieved all this info from him when I ordered all the coolant system hoses.

 

[Aharon]

You are correct on the passenger side to bypass you would replace the T with a straight pipe. On the driver side the T is actually the lower hardline underneath the heater valve above the valve cover against the firewall. It splits into two going to both the front and rear heater cores. You would take this pipe out and run a hose from the bottom of the curved hardpipe to the front heater core inlet on the firewall. Or you could cap off the end of the hardline that goes to the rear heater core (the lower of the two) and cap off the rear heater inlet.

 

[OGBeno]

The rear heater hard lines that go over the tranny hump are a pain in the butt, but worth it to replace of you live in the rust zone or if you use your rear heater--I do since I sleep in the cruiser with the dog in the back, so having some rear heat is key during a cold night.

The rear heater pipes going over the hump are two hard lines with soft lines at either end. The hard lines are welded together by a bracket. I cut through the bracket and snaked up each line individually which made the process much easier (all things considered).

Don't skimp in this area with heater hose--use good stuff--any of the Gates colored stuff will work (Gates is Goodyear, by the way). In terms of the PHH hose and the hard line, this is my feeling: You can get away with ridding of the hard line and putting one long heater hose from the PHH to the heater valve by wrapping the heater hose in reflective high heat tape. EGR temps are at their highest really, really close to the valve and the pipe that goes from the valve to the side of the head...that said...I just deleted the problem as opposed to compensate for it.

If you check out the "Rust Belt Rebuild" thread I have, you will see what I am talking about with the rear heater pipes going over the tranny hump.

Here are some close-up pics:

IH8MUD.com Forum - View Single Post - Rust Belt Rebuild

 

[Brian894X4]

Beno, I can't thank you enough for those pictures. That and the diagram I have gives me a crystle clear idea of what things look like what I'm working on.

I didn't realize that the rear heater hose was smaller. The outside diameter looks the same. Maybe the inside diameter is smaller so that the hose is stronger and lasts longer? That would make it harder to find hose for it, I'm sure.

Bypassing looks far simplier than I originally thought. It would be really nice to eliminate literally 7 individual soft hoses and 5 metal lines...a total of 15 connections, from the cooling system. The passenger side T-fitting could be eliminated and not even replaced if a one piece hose was used in its place. There is a formed hose there, which would be nice to to have, but might be able to get away a one piece unit. That's yet another hose and two more connections that can be eliminated.

That's a lot less potetial failure points and accessing the heater hoses that are left would be much easier. I like the idea.

 

[Brian894X4]

Don't skimp in this area with heater hose--use good stuff--any of the Gates colored stuff will work (Gates is Goodyear, by the way).

Is the gates red stuff the best or the gates Green stripe?

 

[Brian894X4]

Just to update, I decided against by passing the rear heaters.

After pulling off several heater hoses, they are mostly in decent shape inside and out. Externally, the rear heater pipes and hoses look OK. So, I'm currently in the process of replacing everything except for the rear heater hose system since that's one single expensive part and doesn't appear to be need replacing.

However, I would definately encourage anyone who hasn't, to inspect these lines. My rig has lived in a rust free area all its life and doesn't a spec of it anywhere, but the exhaust has killed off most of the paint on the rear heater lines, so if it lived in a rust area, it would no doubt be in bad shape.

It was just easier to replace stock hoses and not alter the system. But I will have a by-pass hose rigged up and ready to go if the time ever comes that the rear heater system springs a leak in the middle of nowhere.

I do have a couple of questions, if anyone can answer them....

1) I'm reading that the silicone hoses can leak. Has anyone experienced a leaking silicone hose, such as when used to replace the PHH, when constant torque clamps are used.

2) How tight is too tight with these constant torque clamps.

3) Has anyone refilled the block via the rear heater hose just to make sure there is coolent in the block when it's all refired up and is there any reason not to do this? Any chance of overfilling the block? I know, probably silly question.

Thanks.

 

[elhombre]

The silicon hose did not leak for me at all. I used the costant tension clamps also and just tightened them hand tight. I noticed that the new clamps were wider than the old ones and my guess is that they squeeze over a wider area and therefore, exert a greater crimping pressure overall. I could not find a torque spec for the clamps and went a little looser than tighter so that I did not damage the hose. It will be real obvious after your first 15-20 min. drive if a clamp is leaking or not.

You cannot over fill a coolant system. If the radiator cap is working correctly, it will allow the extra coolant to slip by and deposit it in the overflow bottle. When I change out my coolant, I jack up the front of the truck a little so that the top the radiator is higher than the block. The truck is made(designed) this way so unless you park the truck on a downward slope, the top of the radiator tank is higher. Fill it up until it is below the rad. cap opening and forcefully squeeze the upper rad. hose a bunch. This seems to help burp the system. Let it sit for 5-10 min. ( I suggest step #6 ), then repeat. Just pay attention to how much came out so you can compare how much you have replaced. Once you finish, fill the overflow bottle to the FULL line and watch it for a few days. It will need a little touch up until you get the system completely purged. As long as you rad. cap is working properly (i.e. buy a new toyota one), it will work automatically.

 

[80t0ylc]

Forgive me for resurrecting this old thread, but I thought it would be better than starting one that covers the same subject.

After analyzing pros & cons of bypassing rear heater system while doing my PHH last Sept., I opted to do the bypass. I removed both 'T's (supply & return) and replaced with straight heater hose from the firewall connections on front heater system. So the rear heater system was just sitting there, idle, with old coolant still in it. Now mind you, this system had no problems. I just wanted to simplify the existing heating system and it makes sense since the rear heater was rarely if ever used. I got to thinking, if I ever wanted to hook it up in the future it prolly would be a good idea to get the old coolant out of the lines and heater core.

If you've bypassed yours and this sounds like a good idea to you, be forewarned, this is a messy job and you will get wet (with old coolant). I used my air compressor (@ 30 PSI, roughly) to gently, but firmly get the old stuff out. I didn't want to rupture core and I figured flushing with water might leave some water that could freeze and cause problems later on. I took off both of the last two rubber hoses before they go up into floor and saved them for the last step of this procedure. Have catch pan ready as you remove these 2 hoses (your 1st coolant bath). After coolant has drained away get ready for more fun with the air hose. With rubber tipped nozzle on air hose for a good seal, (Don't forget your safety goggles) blow into one of the metal tubes coming from heater core (your 2nd coolant bath). When you think you got all the coolant out, try the other direction through the core (for your 3rd coolant bath). Now the core is done and all that's left are the lines coming down from the firewall. I would recommend blowing from firewall end so you don't get old sticky coolant all over that nice clean engine. Also, you've got coolant on frame, exhaust pipe, center diff and drive shaft already - what's a little more? I used a length of heater hose to help get at US DS metal tube at firewall. I was able to shoot coolant over top of center diff. and make coolant puddle under drivers door while blowing out lines from firewall end (at least you don't get 4th coolant bath). Well, you're almost done. I got water hose and nozzle and sprayed off all coolant from all previously mentioned parts and bottom of floor pan and let drip dry for a while. Last step is to take 2 short hoses previously removed and if you got them off intact and they're still in good shape, re-install them, clamps are not necessary at this time. If you had to mangle them like I did, cut off bad parts and bend them into a U shape and put one on core pipes and the other on the end of tubes coming from firewall. I also plugged the firewall end with some rubber plugs and silicone to hold them in place for good measure. Now your unused rear heater system should be good and protected if you, or a future owner, ever decide to hook it back up.

 

[sandcruiser]

i don't think anyone mentioned it- but once you bypass the hoses, you can pull the 2nd heater core. That give a bunch of extra space under the passenger seat. Good for storing stuff.

 

[scottm]

I never got aroung to draining my rear heater, it ended up somewhere on I-80.

 

[80t0ylc]

i don't think anyone mentioned it- but once you bypass the hoses, you can pull the 2nd heater core. That give a bunch of extra space under the passenger seat. Good for storing stuff.

Sandcruiser,

Thanks for info! Do you have to remove passenger seat to pull rear heater core? My FSM is sadly lacking in diagrams and info on rear heater.

 

[sandcruiser]

Yes. You must pull the pass seat to get the 2nd heater out.

I'm referring to a 91 80 series, not sure if the lexus or the later 80 series has the heater under the center console or not.

but in the 91, I pulled the seat, then pulled the heater core. make sure you disconnect the pipes/hoses from below or you'll never get it all out.

To plug the hole I did a ghetto fab fix of putting peal n seal both above and below the opening. It is about 1.5" x 1.5" IIRC. A better solution would be (will be) to put some sheet metal there and weld or otherwise affix it. I'm thinking of using an aluminum sheet and some rivets - applied from underneath the truck.

I gained about a large shoe-box of storage. I have ~20ft of air hose coiled up there. Easy to pull out through the rear passenger door to inflate all 4 tires.

 

[80t0ylc]

Nice, I like the idea of more room, I just need to scope it out and see if my '94 is set up the same. I like your idea with the air hose! Thanks for info!