No heat at idle - did we ever find a solution?

My 2000 V8 is exhibiting what seems the be a common Toyota truck issue - no heat at idle.

I scrolled through many posts here and on other forums, I checked you tube... I think I did most of the common fixes, like adding coolant and making sure my levels were proper, that the overflow worked well, and blowing the lines by disconnecting them at the firewall.

So, the current symptoms are:

1. Truck runs well, no overheating issues at all (133k miles) and it comes to operating temperature fairly quickly
2. No heat at idle, the compressor is blowing just cold air
3. If I rev it in park to 1100rpm or so, heat comes out, and it heats normally while I am driving

Has there ever been a confirmed solution for this issue? My last thought is to replace the thermostat, as I saw it mentioned in one of the treads I followed.

Any other input? Has anyone had this issue and if so, did you fix it and how?

Thank you!

 

Water pump could be suspect as well. Maybe it’s just not enough pressure at idle.

 

Interesting, that was not on my radar. I believe it’s been changed at 90k when my dad did the belts. I have to verify.

 

Here’s a thought. Maybe you could disconnect the hoses going to and from the heater core. Install a clear piece of tubing in between the two. Warm your truck up and see if coolant is flowing through the tube. Start first with just feeling the hoses to see if they are coming up to temp.

 

I am not sure I understand the system well, but wouldn’t this be redundant if I know I have heat? My only issue is lack of heat at idle, not lack of heat at all.

 

I understand. But feeling the hoses that lead to the heater core at idle to confirm whether they are continually getting heat is the problem. Performing this test only at idle. One is going to be putting heat to it and the other is headed back into the system. They both should be getting hot. Meaning it is flowing through the heater core.

 

Thermostat all day

 

Change your thermostat its likely the problem and cheap.

 

Yeah. Thermostat. Did dad change that when he did the TB and WP? Never had one go bad on the 02’ but had another vehicle years ago that was doing what you describe and it was the thermostat which was a simple fix. Are they easy to change on our 4.7 motors?

 

He didn’t change the thermostat for sure. They are easy to swap, so I’ll do it ASAP - I’d prefer to have reliable heat this winter.

Thanks!

 

Take pics.

 

I'm going to replace my thermostat when I do the radiator. Didn't even know where it was located. Found this funny woman on Youtube that made a video about replacing hers. It looks easy. Not even a one beer job.

 

Does the blend door require vacuum to get you heat? Maybe you have a vacuum leak and there isn’t enough to pull the blend door to the heat position at idle.

 

It’s possible - I have no clue. I bought the thermostat and I might take the cars out of the garage tomorrow, pull the hood as far as it goes and plug in a few heaters and replace the it. High of 45 tomorrow, should be doable.

 

If it's a plastic blend door make sure it is not deteriorated.

 

Replaced the thermostat today. Didn’t take any photos, it is really a super simple job, took maybe 15-20 minutes to do.

I didn’t lose any coolant at all, but the truck was slightly low. Knowing that we recently had it topped, I think I might be losing some coolant somewhere and I’ll tackle that when it gets a bit warmer. I topped it one more time and I’ll keep an eye on levels.

As for the heat, inconclusive results. It blew cold, until I revved it once. After that, it blew warm on idle. I’ll have to test it a few more times.

 

Not sure if this might be your issue, but I had a similar problem in a first gen 4Runner V6. Lots of bends and curves in the cooling lines, places for air bubbles to get trapped (airlock). At idle, I had no hot air. But shortly after revving, I could feel heat again.
The higher rpm increases the pressure in the system forcing the trapped air to move through my heater core allowing for coolant-heat exchange.
Did a couple cooling system flushes, but ultimately had to put a burping cup in the radiator cap, put my truck at a near 45° angle, revved the engine sporadically, and eventually got all of the trapped air out. After that, continuous heat through the rpm range and was never a problem again.

 

Thanks for the info, I’ll have to read watch that option and give it a shot!

 

You definitely should lose coolant. You probably need to bleed the coolant system of air.

 

I haven’t had a chance to run a full test yet to see if thermostat change fixed the issue, but apparently I should be “burping” the system after the change anyway, so I’ll be doing it when I get a chance.

 

I've got a 99 tacoma, it was doing the same thing, at idle it had no heat, after taking off from red light or stop sign, it would blow hot air. I check the coolant, it was low, topped it off and the heat worked great. Then is started doing it again and I noticed a slight coolant drip, water pump was leaking, replaced the water pump and everything else that is involved in that, problem solved.

I know we don't have the same engine, but my guess would be your water pump.

 

It is a possibility - my dad can't remember if they changed the pump when they did the belt. I'll have to look at it as soon as it gets warmer. Thanks!

 

A water pump is one of those parts that might last 200k miles or it might only last 5k miles. So just because it got changed kinda of recent, doesn't rule it out.

 

Another thing I’m coming to understand about older vehicles is the coolants and interval changes become necessarily more frequent due to the age condition of the internals. Same vehicle part that lasted 60k miles for something may reduce down to 45k miles with age on the second go around interval.

 

Maybe this will help.

https://youtu.be/OivwKhMyLxs

 

I’d change thermostat because it’s most likely that and it’s the cheapest and easiest. But could be low on antifreeze also. Have you checked to see if you can see the weep hole leaking from the water pump? Pump could be going out. Could also be a clogged up heater core. Have you checked the lines running into the firewall for temperatures? Wouldn’t think head gasket because of you saying no over heating issues. I’d check coolant level and stat first.