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I could use some advice please...

988 views 11 replies 6 participants last post by  Spencer43783 
#1 · (Edited)
Hello everyone,

I have been having a case of the luke warm heat in a 99 Cherokee Sport 4.0 liter, (edited - thank you tjwalker for the heads up!)so I read through the threads and over the weekend I flushed the heater core, replaced the thermostat, temp sensor and refilled with coolant.

I was able to get the heater to work fine and I parked it outside for a bit before I left the garage. Before I left I popped the hood and noticed the reservoir for the coolant was empty so I put more coolant into it and shortly after that the heat went back to luke warm again.

In 9 degree weather not having good heat is a killer - so I'd like some advice. I used a 50/50 blend coolant, thermostat is a new STANT and the flush of the heater core came back clean.

How would adding coolant cause the heat to stop working properly?

I'm open to suggestions, ideas or any help the forum see's fit to offer.

Thank you in advance,


Dean
 
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#2 ·
Dean,

First off, it is important to always post the year/engine at the start of a thread. Filling out information about your Jeep in the profile is also recommended.

Sorry to hear about your heat problem, it is a very common thread topic this time of the year!

What you did was a good approach. I wouldn't be too concerned about having to top off the coolant reservoir after you have done some cooling system work.

1. What is the coolant temperature reading on your dash? Your target is a solid 200-210. Cab heat is a byproduct of engine heat, so we have to be SURE that the coolant is staying consistently hot.

2. Flushing a heater core can, but does NOT guarantee restoring of function to the core. You still could have a clogged heater core.

3. Ensure that the blend door/HVAC controls are working and routing the heat properly.

4. If yours is an 84-96, you have a HEATER CONTROL VALVE. They fail often. Replace it if yours is of that vintage.

Good luck!
 
#3 ·
The controls for the direction of the air work well - when I turn the controls for temp to cold it does get cold. The blend-air door - does this require me to pull the dash or is there an easier access point to it?

What is really confusing me is that it was working - I drove the vehicle for about 5 miles and had heat. Right after adding the second round of coolant the heat went back to luke warm at best.

Coolant temp on dash is right at 210 - just where its supposed to be. Can I operate the vehicle without a thermostat? I'm wondering if I have been getting a batch of bad ones? (yeah, long shot I know)

As always input is greatly appreciated.

Dean
 
#5 ·
I removed the hose from the thermostat housing that feeds the heater core and turned on the engine - cooland came flying out so it appears the water pump is working somewhat. I don't have an overheating problem at all - engine NEVER gets above the 210 mark on the factory temp gauge. I have also replaced the temp sensor to make sure I'm getting an accurate reading.

I am going to try the hose reverse trick I read in another post and see if I can get heat that way. Otherwise it will be a LONG night in a VERY cold garage flushing the darn core again.

What mystifies me still - is why was it working...then after I added some additional coolant is went back to luke warm.

Thank you for your post - greatly appreciated.
 
#6 ·
You said you added to the overflow because it was low. Did you pop the rad cap and see if the radiator was low? It's possible that the system didn't get burped properly and you just have air in there.

If that's not the issue your problem most likely lies somewhere in the heater core/heater core hoses. The heater core hoses kind of 'T' off the main lines and when there's not enough fluid in the system to allow it to flow through the core that's when you'll have the 'no heat/intermittent heat'. You can try back flushing the heater core by reversing the hoses and running it. It may or may not break something loose and let the heat work. It's kind of a shot in the dark.

Have you noticed any out of the ordinary fog on the windshield, sweet smell in the cab, or dampness on the passenger floorboard?

As someone else mentioned the waterpump may also be a possible suspect. The temps are starting to get cooler outside so you *may* not notice an overheating problem if it exsists. The fins could be all or partially missing and limiting the flow of coolant through the heater core. I would just start with burping the system then move onto back flushing the heater core and see what kind of results that yields :thumbsup:
 
#7 ·
I should have mentioned I replaced the heater hoses during this process. I connected a hose to the lower hose that feeds the water inlet pipe and flushed the heater core that way.

To validate the water pump (and this could be wrong so please correct me) I pulled the heater core feeder line from the thermostat housing and turned the engine on. Since cooland shot all over I figured the water pump was working effectively.

I'll burp the system as soon as time allows and hopefully it will allow me get some heat back!

Again - many thanks to all those who have replied, your opinions are valued.


Dean
 
#8 ·
To validate the water pump (and this could be wrong so please correct me) I pulled the heater core feeder line from the thermostat housing and turned the engine on. Since cooland shot all over I figured the water pump was working effectively.
Your test unfortunately isn't fail safe. The impeller on the pump can get weak and you'll never know it with that test.

On a 99, it should and usually almost always does, burp itself in about 3 complete cool down to heat up cycles.
 
#9 ·
I purchased a new water pump for such an event - I'll have to put it in to see if it works. On the drive home this evening the heat was marginally better (I have a 45 mile drive) but the heat was never HOT.

When I did arrive home I popped the hood with the motor running and both hoses were pretty hot, but not so much I couldn't touch them. I'll swap the hoses at some point this week to see if the reverse flow into the core helps at all.

Tomorrow morning will be the 3rd start up and cool down period as I trek to the office again - hopefully any air will have burped out of the system and the heat will continue to improve. I recall last year prior to the system flush and thermostat replacement the heat was great - at full on you could barely stay in the thing in the dead of winter.

Ah...blissful memories. ;)

My thanks to you all and I look forward to future replies.

Dean
 
#10 ·
Sounds like it just needs more burping?

---------------------------------------

Burping- (just my way. 96, open system)

Park XJ with front drivers corner highest by say 2-3 inches.
Check that the tube from radiator filler neck to Coolant Recovery Tank (CRT)
is in good condition. Heater control to full hot setting. Fill system thru Rad Filler, Fill CRT to full MARK with proper coolant mix.
(Not less than 30% coolant, Not more than 70%. or 50/50)

Install 16 lb Plain radiator cap, Mopar OEM or Stant preferred.
(195*F Stant super or Mopar thermostat)

---------------------------------------
----DO NOT OPEN RADIATOR CAP AGAIN. PERIOD.
----IF YOU DO, THEN START OVER FROM TOP ABOVE. PERIOD.

Run engine 5-8 minutes to thermostat opens (upper rad hose shifts to hot to touch. ) Engine off and allow to cool several hours, (couple of hours if oulside temps near freezing) Check level in CRT- during warmup it rises and/or bubbles, During cooldown level drops. Add coolant to CRT, as needed, to keep between 'FULL' and 'ADD' marks.

Repeat 'warmup engine and cooldown' as needed (2-4 times) untill level in CRT holds between the add and full marks fully cold and fully warmed up.
----------------------------------------

Fully burped- CRT level varies 1/2 - 1 inch cold/hot normally.
IF its NOT changing level,that is a CLUE that system has air leak.
Dropping level is CLUE system leak or needs burping.
A good system only needs a few ounces coolant added per year.


Make note that the CRT is physically BELOW the top of the radiator. So what this system is doing is using the expansion of coolant, from the engine heat, to push the air DOWN and out thru the CRT, THEN pull only coolant back as the engine cools.
IF the radiator is opened, it lets air INTO the system. (OR any air leak)

Air in the system on top of the cyl. head REALLY messes with the cooling where its needed most.
Also the temperature sensors give very erratic readings, if in air, to ECU and TEMP gauge.


Good Luck,
Tex96
 
#12 ·
I agree to a point. But who's to say deposits haven't started forming on a bend and then a nice chunk of old coolant doesn't hit that point in the heater core where the diameter of the pipe is smaller? And then you have a clogged heater core.

Which way do you think a chunk of something will flow more freely: through the partially clogged pipe or a clean pipe?

I don't remember anyone saying backflushing/flushing the heater core is a 100% guaranteed method for unclogging a heater core.

You can try back flushing the heater core by reversing the hoses and running it. It may or may not break something loose and let the heat work. It's kind of a shot in the dark.
2. Flushing a heater core can, but does NOT guarantee restoring of function to the core. You still could have a clogged heater core.
:dunno:
 
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