1999 GMC Jimmy - No heat

[lester_26]

About 3/4 of the way through last winter, my heat went from hot to barely warm. This winter I have very little heat.

A/C works fine..all controls work fine (except for 4x4 which I'll post next).

I had my transmission flushed ~ 2 years ago...

Suggestions greatly appreciated....

LESTER

[DelCoch]

Does it have climate control or just regular controls for heater? When was the last time the radiator was flushed and new coolant put in? What kind of coolant does it have in it - orange or green?

[lester_26]

Radiator was flushed 60k miles ago. Has orange fluid. Regular controls for heater.

I did some minor trouble shooting by reading the forums..here's what i know.

I was parked on a 5 degree downward slope (my driveway) and noticed the level was a bit low. I added some coolant. I opened up the rad and noticed I could not see the level (front end of the vehicle being lower than the rear..this seemed odd). I added a total of ~ 1 cup of fluid.

I started the vehicle and felt the hoses in and out...no heat on either. Waited ~ 3 mins and neither got warm.

One other observation (if useful at all) is I saw that I was on the "low" end on the coolant in summer time. I filled up to high, went for a ride and found that a bunch of coolant sprayed out on the road. I was then back down to the low level....this situation never returned..

[DelCoch]

Originally Posted by lester_26

. . . I started the vehicle and felt the hoses in and out...no heat on either. Waited ~ 3 mins and neither got warm...

It will take more than 3-minutes for the heater hoses to get warm. The engine has to be up to operating temp. What does the heat gauge read after driving for 20 or 30 minutes.

At 60K you're over-do for another coolant change and flush. Check this post in the the "How To" Section.

[lester_26]

Thanks for the info!

I read over the thread and found I should get

2 gallons of distilled water $1
2 gallons of antifreeze $16
Prestone Flush 'N Fill kit $3
Prestone Radiator "Flush" $3

Can you clarify a couple of items:

1. I see three hoses on the left side of the rad. 1 from the overflow, 1 goes from the rad to the base of the engine and the other from the top of the rad to the heater core. The flush goes through the heater core to the base of the engine correct? Direction important?

2. What is the easiest way to drain the fluid? A plug on the bottom of the rad?

3. How much fluid does a 1999 gmc jimmy hold?

4. Finally, should I be worried that I had coolant overflow through the overflow line in summer even though it was never overfilled?

[DelCoch]

The heater hoses go into the heater core on the passenger side firewall. They both run up the passenger side of the engine. One hose goes to the water pump and the other one connects to the engine. I think what you see on the left side of the radiator are the engine oil cooling lines.

Before doing any flushing I would get the engine up to operating temp, (drive it for 20-30 minutes) and check the heater hoses again.

If the engine temp is getting up to 180-190 at least one of the heater hoses should be hot. When the heater control valve is open, (heater control set to max heat) both heater hoses should be warm; which indicates coolant is flowing through the heater core. If one hose is hot and the other one cool, there’s an obstruction in the heater core; or the control valve is not being opened up or there is an obstruction in the valve, or the valve is defective.

If both hoses don’t get hot I would disconnect both of them at the engine end and with the heater temp control set to max try to run water from a garden hose (at low pressure) into one hose and see what comes out of the other hose. If a lot of crud comes out, get it to run clear and then do the radiator flush. If you can’t flush water through the heater core, on either heater hose, then you’ve found the problem. Sometimes a hose will disintegrate on the inside and become blocked. This usually happens near the end of the hose.

The easiest way to drain the coolant is by opening the drain cock on the bottom of the radiator. This will drain the radiator, but it won't drain all the coolant out of the engine, but after you flush it the water left in the engine will be clean.

Your radiator + engine holds 11.9 Quarts = 2.975 Gallons of coolant. A 50/50 mix will require 1 ½ gallons of straight antifreeze, but I would put 1 ¾ in. I would put 1 ¾ gallons of straight antifreeze in first and then add any needed water to fill it up and then top it off with water after running it or add the rest of the 1 3/4 gallon if it didn't hold all of it when you filled it. Otherwise, you’ll never get 2.9 gallon of 50/50 mix in it, as the engine will be holding some water.

I wouldn't worry about the loss of coolant during the summer if it was only a one time thing. But I would keep and eye on it. It would be best to do a pressure test with a radiator pressure test gauge, which can be borrowed from AutoZone, etc.

[Schrade]

GM Red coolant plug in the heater core.