Cool heat

[Brownie92]

2000 DII 107K miles
It has been fairly cold here around -6F and my heater is just not keepin up. I usually start my truck around 30 min before I leave. When I go to leave the temp guage is in the normal range but the vent is blowing cool air. The temp guage never goes above the normal range.
The live data from my OBDII shows coolant temp at 194-200F but the vent temp is 70F at idle and 90 at higway speed @ 2500rpm.
As a test I put cardboard completly blocking the radiator.
The coolant temp came up to 216 but at idle the vent temp did not come up. On the highway the vent temp came up to 126 but when I stop the vent temp drops quickly.
I have had a small coolant leak from somewhere I can't find. There is no water on the floor or indication that the heater core is leaking. I have had the "slosing dash" for a while and occasionally have to add a quart or two of coolant.
Is it possible for a water pump to partially fail?
Is there some valve to the heater core that is not opening?
Is there a giant air bubble in the heater core that is stopping fluid flow?
Thanks
Mark

 

[Disco Squared]

The small coolant leak has probably created an air bubble in your heater core, hence no heat.
Short term fix--bleed your coolant system to eliminate the trapped air bubble.
Long term--find the leak and fix it. The coolant is probably evaporating as it leaks, so the leak is not creating a puddle. Look for white streaks at the bottom and rear of your engine and bell housing, also look at your throttle body heater. Those are the popular places for leaks to spring up. Good luck.

 

[Brownie92]

Thanks, What is the best/easiest way to bleed the system?

 

[Disco Squared]

Start your engine. Loosen the black plastic bleed screw on the radiator hose that's on the top of your fan shroud. Loosen it up quite a bit, but be careful not to let it blow out of the hole under pressure. Add coolant to the reservoir as your engine idles keeping it at the full level. You should notice air escaping from the bleed screw. When you get a solid flow of coolant from the bleed screw, tighten the screw. You may have to drive around for awhile and repeat the procedure to get all the air out. The above has worked for me but I've also heard that parking on an uphill slope while bleeding the system works good too.

 

[Brownie92]

Part II

I tried to bleed to air from the system but I immediatly got a solid stream of coolant. I first parked on a approx.20 deg hill nose up and never got any air. Then I turned around nose down and just got a steam of coolant.
Is there more to this procedure ?
Should I drive around with the bleed screw slightly open?
Thanks in advance
Mark

 

[Disco Squared]

Should I drive around with the bleed screw slightly open?
Mark

No, I wouldn't try that.

Here's a static bleed procedure used for servicing the cooling system you can try. Also was your heater set to full hot?

COOLING SYSTEM - V8
26-2-14 ADJUSTMENTS
5. Release top hose from retaining lugs on the fan
cowl, leaving the hose to rest on the lugs.
6. Remove bleed screw from top hose.
l 'A' From 03 MY
l 'B' Up to 03 MY
7. Unclip the bleed hose from the battery box.
8. Remove expansion tank from its mounting
bracket. Slowly fill the expansion tank with
coolant, approx. 4 litres (7 pt).
9. Raise the expansion tank approx. 20 cm (8 in)
vertically, coolant will drain into the system.
10. Refill the coolant expansion tank until a steady
flow of coolant is emitted from the bleed hole.
11. Fit the bleed screw then, with the expansion
tank still raised, continue filling the system until
the coolant level reaches the base of the
expansion tank filler neck.
12. Fit expansion tank filler cap, fit the expansion
tank to its mountings and clip the bleed hose to
the battery box.
13. Refit the top hose into its lugs on the fan cowl.
14. Start and run engine until normal operating
temperature is reached, and check for leaks.
15. Switch off engine and allow to cool.
16. Check for leaks and top-up coolant to cold level
mark on expansion tank

 

[Brownie92]

Thanks, and yes I had it on high heat/ high fan. If I have the system flushed by a shop will that get all the air out?
Does the shop have to be smart enough to do the entire procedure?
There isn't a dealer within 200 miles of where I'm at.
Thanks
Mark

 

[Disco Squared]

If I have the system flushed by a shop will that get all the air out?
Mark

Yes, that will probably work.
IMHO--if you're going to take it to a shop, have them pressure check the system to find the leak. You will continue to get air bubbles until the leak is fixed.

 

[Brownie92]

I thouht about the presure test, I think I will have it flushed for now and wait to have the pressure test. My guess is that after the test the "small" leak wont be small anymore and I will have to fix it. I don't like working out in the cold, so I will just have it flushed for now and hope it gets me through winter. Then in the sprong I can tackle the leak.
Thank you for all of your help.
Mark

 

[Brownie92]

Final Chapter

I just thought I would post this in case someone else had the same problem:
I took it to a shop to have it flushed and they were less than helpfull and basically told me I was crazy to think that there was air trapped in the heater core. (Visits to shops like this remind me of why I do everything myself)
So rather than given them my 100.00 I went to Home Depot and bought a garden hose replacement couple. The kind that would be on the faucet ent of the hose. And a hose valve that is designed to go on the faucet end. By hooking them up I was able to have a 5/8 inch hose barb on the end of my garden hose with a valve right there.
I unhooked both the heater core hoses and connected the garden hose with a clamp and slowly turned on the water. Nothing but air came out for quite a while then a little antifreeze. I ran it until nothing but water was comming out and then hooked it back up. I also used this as a time to disconnect the top radiator hose and filled it also. This was all done at about 168F of enine temp. Now I have nice toasty heat.
Thanks for all your help.