My friend brought his '98 4WD 4Runner over today so that we could install the same Wheeler's sway bar kit as I did earlier in the week. A few seconds after sliding under his truck, I happen to look up and see two completely corroded pipes running along the passenger-side frame rail. They were dry but absolutely rusted into oblivion. We quickly realized that these were the supply and return pipes for the rear seat heater under the passenger seat. My friend reached up to simply touch the pipes and was immediately showered with a rush of hot coolant. By the time the shower was done, at least half a gallon had emptied from the system. After a few minutes of high-level strategizing, we decided to disable this feature, as he never really has anyone in the rear seat. To do this, we cut and yanked the rest of the garbage out and then fashioned two U-shaped lengths of metal pipe. The first "U" was used at the firewall to connect the two rubber hoses and effectively create a simple continuation for the coolant. We had a pipe bender, the right diameter metal brake line, and a flaring tool. The second "U" was used to close the loop under the truck where the two rubber lines exit the floor under the passenger seat.

We did not have a camera handy, but I'll gladly answer any questions. I may be able to grab a few shots of the repair tomorrow.

I posted this because the coated steel lines could have failed at any moment, causing an immediate loss of coolant. Please get under your 3rd Gens as soon as possible to check these lines. My friend has never driven on the beach and has owned the truck since new. We recently ran into a similar corrosion problem with his power steering hard lines. In that case, we formed our own new lines and the steering works fine again w/o leaks.

I hope this helps!

Andreas

 

Well I just had the same exact thing happen to me at 7 AM, 9 degrees out and on the way to work. Luckily I was only at the gas station down the street when I noticed.

After playing there and then back at home I figured out that i wasted all my time. The fix is as noted above - except much more simple.

The run to and from the rear heat is in the engine compartment back on the firewall. Disconnect one rubber line from the metal line going to the rear heat and remomve the other line from the outlet to the rear heat. Then connect the lines to the rear htr together with the hose. Then bypass the rear heat by connecting the other hose at the rear heat 'valve' (where the cable is). This bypass only took 1 minute but could have saved me 5 hours of numbing pain and frustration as I tried to fix it in the driveway.

Hopefully everyone comes to yotatech prior to starting to work on it!!

 

'Tis indeed an easy fix, but annoying nontheless. Thankfully you caught it before venturing out onto the highway.

Andreas

 

Awesome solution came in real handy today. For over 8 months I couldn’t tell where coolant is leaking from as it would burn/evaporate before it hit the ground but I can smell it burning. Finally noticed it dripping from one of the two rear heating pipes below the front passenger seat and this solution saved me time and money. I must say that it took about ½ hour to reroute the pipes to do the bypass of the rear heat pipes. You really have to be careful dislodging the hoses and hooking one back as you may cause damage breaking the other adjoining lines. Thank you, guys.

 

Just found the same issue on my '98 as well. Quick fix too. I like having the heater back there though so I'm gonna run some new lines when I get a chance.

 

Aren't the lines aluminum, except for the rubber hoses?

 

Nope. The cores may be aluminium but the lines are steel.

 

i remember when i first read this thread a few years back, i checked the lines under my truck and saw that they were aluminum. there are three part numbers on toyodiy (2 USDM and 1 JDM).

 

I think some of the later 3rd gens were stainless steel but not 100% sure.

 

Same thing on my 1995 4runner 3VZE. Had just replaced the heads and noticed water dripping under the car. In that moment of terror, thought that it was leaking from something that I put together wrong. It turned out that the heater lines were just rusted and water was leaking from them up near the firewall. I did the same, just turned the same rubber hose from the supply side and connected it to the return. Been fine ever since.

 

hey new here,i have a coolant leak from the same area as heater hoses. only problem is i cant see in there to fix or find the issue. how did you guys get a good view ?

 

Shouldn't be a problem to locate lines, roll underneath and you will see something that looks like dual fuel lines. Follow them to the console area, and up front to the engine compartment.
Mine were almost to go, but the wife said there was no way I could just block them off if I ever expected her to ride in back !

I used rubber fuel line (the heavy stuff) and routed it inside the frame. Doubled hose clamped it everywhere. Wherever they lines came in contact with a sharp corner or entered/exited the frame rail thru a hole, I wrapped them with that plastic tubing protector. 4 years and all is well, plus if I ever have line trouble, all I need is a knife and a screwdriver to do the return loop thing and keep going.

 

Thanks for that, I have since found it was a corroded frost plug leaking coolant