No rear heat

[One_96TR4]

I'm not really sure what the deal is, but it's never worked. I bought the truck last summer and the rear heat doesn't seem to work. The fan comes on and blows cold. The front heater blows as hot as ever but the rear won't get hot for the life of me. What might be the problem here. It's not a HUGE deal but it would be nice to have the rear heat working. I always have my rear passengers complaining that it's cold in the back but I turn the heat off or down because I'm roasting. Anyone have any idea's?

[04 Rocko Taco]

Check the plumbing....
my bet is your missing some piping under there.

[MTL_4runner]

First I have no idea what model or year your truck is so I'll assume it's a 4runner. You should make sure you have the slider set to hot. Next be sure the blower is working. If it continues to blow cold air, you need to check the hoses up in the engine compartment to be sure the coolant is circulating through the rear heater core (see attached pic). If all of these are good then you should have heat.

[One_96TR4]

Ok well I seem to have found part of my problem. I popped my hood to check them out and to my surprise the lines running the rear aren't hooked up. I was going to hook them back up but I don't know what to re-connect and where. Can anyone tell me what I might need to connect these back and which lines connects to what? Also seeing that these lines must have been disconnected by the PO it makes me wonder why. I think there may be a possiblity that they were leaking otherwise what would be the motivation to bypass them. I'll have the check them out before I reconnect them. Anyone have any idea's as per how the check them for leaks. I was thinking maybe to just hook them up and see if it leaks anywhere.

[One_96TR4]

Sorry Jamie I didn't check the posts before I reposted my findings. Yes I have a 96 4runner. I'm going to try and use that pictures and hook back up the hoses and see what I get. As I mentioned them being disconnected leaves me to think there was a leak or something for them to be disconnected in the first place. I'm going to hook them back up and see if I can spot any leaks.

[One_96TR4]

Well I hooked up the lines properly as per the pic posted above and I have HEAT. It's kinda nice having it now after being used to not having it. Back of the truck warms up a lot faster now. I haven't noticed any leaks as of yet but I will be keeping an eye on it for the next few days. Hopefully nothing will show up but I guess I'll see in the next few days.

[MTL_4runner]

Do keep an eye out for leaks because the hard coolant lines that run along the underside of the truck may have leaked in the past causing the prior owner to disconnect them (it's a fairly common problem so I wouldn't be the least bit surprised). You may want to go under the truck and inspect the lines for rust areas or leaks and if you find any, replace the bad sections with rubber hose.

[One_96TR4]

You may want to go under the truck and inspect the lines for rust areas or leaks and if you find any, replace the bad sections with rubber hose.


Haven't noticed any leaking yet but just out of curiousity, If I do find there's a leak would it be a good idea to use rubber hose as a replacement? I mean don't the hard lines run right next to the exhaust? It might be fine but I've never done it or seen it done so I figure I might as well ask.

[MTL_4runner]

Haven't noticed any leaking yet but just out of curiousity, If I do find there's a leak would it be a good idea to use rubber hose as a replacement? I mean don't the hard lines run right next to the exhaust? It might be fine but I've never done it or seen it done so I figure I might as well ask.


Obviously they used hard line originally for exactly the reason you mention. Replacing the entire hard line would certainly be the best course of action if you find a rusted out section, but you might find that quite a difficult task due to all the bends and angles involved (although I could be wrong since I haven't done one yet myself). Rubber hose with clamps can also be substituted, but those areas probably need to be protected with some sort of a heat wrap to shield it from the heat of the exhaust. It wouldn't be so much of an issue in winter, but summer temps can get quite extreme near the exhaust.

[One_96TR4]

Well it's been awhile since I reconnect the rear lines and have had my rear heat working. As some may have already read my car was vandalized a few days before new years and I just got it back today. On the drive home I noticed that my temp guage was spiking higher than it normally reads. It went almost to the red when I caught and turned on the heat to bring it down. Once the heat was on it managed to stay normal. I stopped and checked my coolant at the gas station and saw that it was low and topped it up. I have reason to believe that this may have something to do with me reconnecting the rear heat lines. I'm not really sure what or where I should start looking. I don't see any noticable leakage. I did notice that for a while the rear heat was blowing cold but seems to be blowing hot again. Only other issues I have with the car at the moment is an exhaust leak upfront before the cat. I think it's right where the collector is and the exhaust bends to come under the truck.

[MTL_4runner]

Have your cooling system pressure tested and you should find any leaks.
Also helps to use a blacklight for finding the coolant leaks.

[One_96TR4]

Have your cooling system pressure tested and you should find any leaks.
Also helps to use a blacklight for finding the coolant leaks.


For the time being I bypassed the rear heat lines. It's just too cold outside for me tot be playing with this right now. I'll wait until it warms up a bit to diagnose the problem. I really appreciate the help though. I'll get back to this thread once I start checking things out and find the problem.