So here's my story 2000 DSII heats been working good until a few days ago. I checked the coolant level it's fine. I don't hear the telltale gurgling inside the truck when coolant is low. Engine temp is fine. Head gaskets and radiator where done last February heat had been working fine. Feeling the hoses going to the heater core the one closest to the engine is hot while the one closer to the fender is luke warm.

Doing some reading I belie I understand how to bleed air from the system when the truck is stone cold ovet fill the expansion tank and open the bleed vent in the hose over the thermostat(is that correct). Do I need to unbolt the expansion tank and lift it up?

What are the odds there's an air pocket in the heater core? will this bleeding method address it if there is one.

What about the heater core being blocked? how common is that? I ask because I just ran into that problem in our VW. and had to fill it with CLR overnight then back flushed it with the air hose(water hose for the hose was frozen, this stuff only happens when it's 20 degrees fernheight or less).

And advice greatly appreciated.

 

no bolts in tank.. lift up on filler side, slide that direction and presto. grab a bungee or something and hang it higher than the rest of the cooling system. I like to park on a front incline. then that bleed process should work..

no on direct core fill
yes I would lean towards blockage. any miracle bs additives, added as a stop gap, before hg job? that would be a drawback to said stuff.
if the bleed does not prove helpful. I would do a heater core flush. both directions, back and forth. I use a dishwasher hose attachment.
I have used clr with success, but it recommends to avoid use on aluminium
good luck

 

You might be surprised at just how much a single old leaf can block air flow...... no joke. Super easy to check and clean though. Just remove the heater blower fan and inspect/clean. I hope for your sake that is the source of the issue..... no heat in winter time is no good indeed. Good luck

 

I have a similar issue. I have had heat in past years, but now I have heat when I am idling for a while, but as I drive at any speed to speak of I lose heat, just cool air blowing then. So, does this mean I need to try harder to get that dreaded air pocket out, or would this lean more to sludge/muck in the heater core?

 

the heater core unfortunately is the highest part of the cooling system on a DII, even fully bleed it will still hold air. Sometimes the best thing is to bleed it again and take it out for a good run.

 

Park it on a steep hill and bleed it. (Nose up)

 

This is the case. You can park it as nose high as you want but you will never get the heater core outlet above the top of the heater core. Take a look at a picture of one on a parts site or in RAVE. If you manage to drain the coolant out of yours, you just have to fill the system and bleed it as best you can then take it on the highway and get the coolant flowing. The air gets pushed out by flowing fluid.


I would suspect a blockage in the fluid flow. Backflush the heater core with a garden hose. On mine, I used a hose nozzle that was tapered and stuck it into the end of the heater hose and held it together with my hands. I was amazed by how much resistance there was initially but it blew out pretty quickly. Now my heat works awesome, even with a 180 thermostat.

 

Thanks for the input. I was planning on doing a complete system flush, but I like the idea of flushing the heater core backwards to see if I can loosen up any debris. I usually put the passenger side front wheel on a ramp, and then remove the coolant tank from its mount and hang it by a bungie from the hood to get it as high as possible. I bleed it slowly until I see no bubbles from the bleed screw, and then let it flow from the bleed screw for a bit longer while keeping the coolant tank full. I have run it and run it and let it sit overnight a few nights elevated as noted, but still no heat, so heater core reverse flow flush will take place, while we have nice warm temps this weekend in Virginia. YEA!

 

Thanks everyone for the responses. I'm hoping its just an air pocket. I bleed the system and it did have air in it. Driving it that day it felt better but not great. So probably a few more sessions in order. That said I have decided that the bleeder on the top radiator hose is leaking/sucking air so I need to fix that first.

I remember having the radiator replaced last year and they used a device connected to the expansion tank to create a vacuum on the system using compressed air. Anyone experience with this type of unit or know if this is a surefire way to get the system free of air?

Thanks again.