At some point the beginning of this winter, I started noticing that my heater was not working properly. Some times had a little heat and other times nothing. I did a good flashing of the system. I installed a T adapter on one of the hoses close to the firewall and by the cold/hot valve and then plugged the garden hose for a few minutes. Then I filled it up with the antifreeze and started my truck until it was warm with the heater all the way up. Now I have heat even more than what I had before. I was thinking that I had to replace the heater core. Just knowing that I had to take my whole dash apart to do that, I did not hesitate to run the flush first on the system and there I had good results. Try that, it might work for you. Good luck!

 

You must have a later model truck. All I had to do to replace my heater core was take the door off my glove compartment, and one heating duct. 40 minute job.

 

You r right, perhaps. I have an 88 4runner and in order to get to the heater core I have to take the whole dash apart, well, according to what I've read with other owners of 87-88 4runners. I never did it, I flash the system and got the heating problem fixed, I thank God I got that done because it has been cold here... What I am dealing with is the cold start. Truck does not want to start and when it does, it stalls. I need to keep pressing gas until it warms up. I will check that Idle Air Control Valve today to see what is going on...I hope i do not have to replace it because its expensive...

 

I finally solved my heat issue. Might have been a combination of a couple of things and then, maybe not. I spent most of Sunday trying to flush out the heater core without making a huge mess in the garage. I rigged up a hose off of the heater control valve to catch all the antifreeze as I used compressed air to blow out the residual left in the core and into a milk jug. After that I used a barbed connector to close the loop so that I could drive the truck out of the shop and into the gravel. From there I used a brass female hose end attached to a section of heater hose to flush out the heater core. I caught the waste in a bucket so that I could see how much junk came out of the heater core and also because I am a freak about not poisoning any animals in the neighborhood. The flow through the core was pretty good, so I hooked everything back up and tested it out. Same results. Heat for a few minutes and then gradually cooling off. OK, now it's personal. I pulled the heater out of the cab, and replaced all the feed hoses under the hood. When I started on this project a couple of weeks ago I had ordered new hoses and a core from rockauto.com. I buy Datsun parts from them when I can and also get the latest discount codes from ratsun.net in the "parts wanted" section of the classifieds.
I installed the new core into the heater box after cleaning cleaning the box and getting all the flappers working smoothly and replacing all of the worn out foam with PVC foam tape from Ace hardware. Every thing now seals tight and no drafts when all the doors are in the "closed" position. This system had a flush out on the hose that goes to the heater control valve that had been installed by a PO. When I replaced that hose, I left it out of the loop. Upon close inspection, there is a very fine crack in the cap. I have been thinking about this and have come to the conclusion that this might be a big part of the problem. The crack was keeping the system from pressurizing correctly and most likely causing antifreeze from fully filling the heater core by way of an air bubble.
I put the whole mess back together this afternoon and drove 30 miles down the Gorge to look at a job. Five mile into it, I had to crack the side window and let some fresh air in as the cab was so warm. Alrighty then, that's more like it. Almost melted my brain. Next on the list, fix the vibration in the front drive line and retro fit some new bucket seats. Everybody needs a hobby, right?

 

Thanks for sharing your solutions, it looks like whatever the problem was, you've managed to hit it on the nose.

For what it's worth, it's not a hobby. It's a disease.
A very virulent strain of the Cruiser Virus.

 

The thing is, I have never really had to do much outside of regular maintenance on this truck. I have rebuilt the motor and tranny once in the 20 years that I have been using this as my daily driver. Recovered the bench set twice, and put a new rear bumper on it once when some lady drove her Ford Taurus under the rear end. I swapped out front and rear drive lines last year as my rear one had slop in the yoke and am about to send both out to get rebuilt by the pros while I am gone for a couple of weeks. I am the third owner and use the hell out of it. I haul tools, go skiing, hunt mushrooms with it. In all that time it has only stopped running one time, at the toll booth on the Oregon side of the Hood River bridge when the ignition ignitor gave out. That was at 168K, I am at 278K now. Never thought of it as a hobby until this last project. More frustrated that such a simple problem took so long to figure out. Should have just gone all in from the get go in retrospect but cured a few other problems along the way, so it all worked out in the end.

 

Thanks for the info exit64. My heat is warmer but i will rebuild the heat sys once I get some down time on the truck. Thanks for sharing the info.

 

FYI, mine has A/C so it is a bit tight getting the heater assembly out. I think there is a lot more room without the A/C unit in the way. That is going to be my summer project. Used to be so cold it would give you an ice cream headache. Nothing really that hard about any of this, just time consuming and working in an unheated garage space really blows.