M1008 only heats while driving

[jelease]

I have a 1986 M1008 I put in a new radiator and thermostat and cannot get any heat while at idle. If I go for a short drive I have plenty of heat. Any ideas where to look for my problem? Thanks in advance

 

[AlexFolino]

Bleed the system, put a bleeding funnel on it and let it run for a good while. until no bubbles come out. Shut truck off and remove plug for funnel(which should come with it) and put the rest of the coolant in the overflow. One other thing, are you certain you put the thermostat in right?

 

[jelease]

Yes it was put in right took a picture to make sure it went in the same way it came out. Where would I put a bleeding funnel on it.

 

[islandguydon]

I agree with AlexFolino, There is an air lock somewhere in the cooling system.

 

[rlwm211]

What is the indicated operating temperature while idling and while driving?????

I have seen a large air pocket be the source of a problem such as this.

The heater hose from the intake manifold is the send to the heater core and there could be a large bubble trapping there when circulation is slow. This is likely due to the arc the hose takes from the intake towards the heater core. The flow is out of the top of the manifold, through the heater core and back to the radiator.

Did you let the engine come to temperature with the cap off? You can hold it at high idle with the cap off and this may 'burp' the air out of the pocket and then you can add coolant to fill the system as it is likely not full at this point. You should be able to see flow into the radiator from the heater hose that connects to the tank on the right side.

Otherwise, you can use the funnel method as described.

One thing to remember is that the heater is on a separate loop from the radiator and actually should be warm BEFORE the radiator is.

If it is not there has to be a bubble.

Hope this helps

RL

 

[blackhueys]

anthother trick I use to help bleed the system is to park the vehical on a hill with the front end facing up this will help to get rid of the air as well when your bleeding it. sounds funny but it works. if that does not work the oother option is to pull a vacume and then suck the coolant in done this a few times as well but you will need adapters etc to do this.

 

[muddobber40]

A blown head gasket can do the same thing.

 

[porkysplace]

Did it have heat before you change the radiator and thermostat ? If not you may have a pluged heater core.

 

[Anubis8472]

Nine times out of ten what you describe is air in the system.
I've never used a 'bleeding funnel' but it might be worth looking into.

Basically any time you open the coolant system you're letting air in, the way it's supposed to work is when it cools and creates negative pressure it draws coolant in from the 'overflow' tank instead of air. (make sure you have coolant in the 'overflow')

Start with the vehicle cold.
Open the radiator cap.
Run the vehicle and let it warm up.
Being carefull of moving parts, you can work the air out of the hoses a little by hand.
Adding coolant as bubles exit.
Wait untill the vehicle reaches operating temp and the thermostat opens.
Once you get no more air bubles out of the radiator, and the coolant is full, replace the cap.
This can be a messy job (I'm guessing thats where the 'bleeding funnel' comes in) also keep in mind once it warms up that coolant is hot, so wear some gloves.

You should pressure test the rad cap any time you work on the system as well.

 

[porkysplace]

Nine times out of ten what you describe is air in the system.
I've never used a 'bleeding funnel' but it might be worth looking into.

Basically any time you open the coolant system you're letting air in, the way it's supposed to work is when it cools and creates negative pressure it draws coolant in from the 'overflow' tank instead of air. (make sure you have coolant in the 'overflow')

Start with the vehicle cold.
Open the radiator cap.
Run the vehicle and let it warm up.
Being carefull of moving parts, you can work the air out of the hoses a little by hand.
Adding coolant as bubles exit.
Wait untill the vehicle reaches operating temp and the thermostat opens.
Once you get no more air bubles out of the radiator, and the coolant is full, replace the cap.
This can be a messy job (I'm guessing thats where the 'bleeding funnel' comes in) also keep in mind once it warms up that coolant is hot, so wear some gloves.

You should pressure test the rad cap any time you work on the system as well.

You also need to have the heater controls on to allow coolant to flow through the heater core when filling the system.

 

[AlexFolino]

http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0

I use these daily, they save so much time and are not expensive at all. Simply fill the funnel with coolant( 1/2 to 3/4 of the way in funnel) and let vehicle run, once it gets to operating temp and no more air comes up, your good to go.