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still overheating and lack of heat... read on....

dellstopjeep

dellstopjeep

NAXJA Forum User
Location
KUNA, ID
So in the last year since I rebuilt my motor in jeep I have had running to hot issues. I replaced water pump and time of motor rebuild. Then I replaced everything in cooling system while converting to open cooling. New heater core since it was partially clogged, new hoses, newer stock radiator, new hd fan clutch, fully functional shroud and aux fan, replaced thermostat a couple times and brand new cap. I think It is air pocket less as it ran today after I replaced heater core at 215-220 idle with aux fan on but needs heat on to not get any hotter. I also have a possibly related issue with my heat, it gets warm but not hot like it should. Even after replacing the heater core that problem hasnt changed. Blender door is functioning properly...... Do I bite the bullet and upgrade to a badass radiator or is there anywhere I can look. Also could there be any other reason for lack of heat? Even though the blower fan seems fine should I look there? THanks needs this thing dialed in for the upcoming snow wheeling season. :cheers:
 
Does your XJ have a Heater Control Valve? Is it plumbed properly? Vacuum hooked up? (although without vacuum, id defaults open to the core). After the engine is up to temp, are the heater hoses warm? One warm, one cold? With a new core, it should run through good, so it would seem the coolant isn't getting there. One thing that many of the folks on here would recommend is the thermostat with the checkball in it. I swear by it, helps get all the air out.
 
I ditched heater control valve and plugged vacuum line. Both heater hoses are hot and coolant is flowing freely. I never tried thermostat with weep hole because they are neve available evem at the schucks I work at
 
The only source I'm aware of is the dealer, and yes, they charge for them. There are a few threads on this subject to look at, but they seem to work for me.
 
Have you check your temp with only stock gauge ? Get your hands on a manuel temp gauge..Is it boiling over? is it pushing water into the recover bottle?
 
The blend doors are, I believe, cable operated, at least on the first gen models. When you cycle the temp. control, can you feel resistance on the knob, or hear a door opening and closing? If you're sure hot coolant is flowing through the core, it's gotta be an airflow issue.
As far as the engine heating, you mentioned a rebuild. This sounds suspiciously like a coolant flow issue inside the engine. The coolant passage at the back of the head that goes to the block likes to clog, but, unfortunately reqiures removing the head to see. Do you have access to an infra-red heat gun? It would be interesting to see if infact the rear of the head would be appreciably hotter than the front, as the coolant is exiting to cycle through the radiator.
IIRC, I saw a thermometer gun at Harbor Freight for around $20, would be a neat toy.
 
I will use a manual thermometer... would I check at the radiator cap? And I dont believe coolant would be boiling over if I just have a overflow tank with the open system correct?

Also I may buy the theremometer gun and check temps around the block and see if that is the case which I hope it is not, I may just replace the blower fan out of principle since its the original and I know its not a cable problem. I adjusted and made sure it works properly.
I was looking at 3 rows from radiator barn so as cheap insurance I may pick up one there as well to eliminate that as the possible issue.
 
If your are over heating it would push water into the overflow bottle..If you have a 195 stat in it, i would say it would run around 210 on a warm day
 
well I took it for a drive today and it ran at or around 205 like it should while driving and with heat on at low setting....but when sitting idle with heat off it slowly slowly crawled to 215-220, it is 90 degrees outside but obviously it is still not maintaining proper temperature without aid. System pressure is excellent as I released safety on cap lots of bubbling from overflow, I think I need to check temperature of coolant with a manual gauge. Where would I check it at with system still staying properly pressurized????
 
Got an infrared temp gun? Go around and check pre and post heater core, radiator inlet and outlet temps and so on. All should be at least 150, with up to thermostat temperature in some spots.

Other basics.. coolant mixed properly, not 100%? Water pump flow, thermostat function, free flowing radiator, fan clutch, electric fan operation, cap holding specified pressure. Air pockets are usually exorcised at the rear temp sensor on the head or by using a vacuum coolant fill device.

Are you sure the head gasket is OK? Any signs of combustion gasses in the coolant?
 
what does your open cooling system consist of? your not using the stock closed system bottle are you
 
no I am using a generic overflow bottle from napa. I think head gasket is okay coolant looks great and is mixed 50/50. I will try to steal a infared thermometer from the electrical distributor work at when there not lookng but I think my next step is a good 3 row radiator. THe good news is it runs at proper temperature unless idle for a while. Defnitly tells me its probably just a small issue now. I dont realy know how I can test water pump flow without pulling everything apart but it is brand new so its hard to believe thats the failing point. thermostat is functioning properly per my boiling water test a month ago. Cap is brand new as of yesterday and proper pressure in system. I will flush and attempt to burp when new radiator is installed. What is the proper way to burp open system since im new to not being pressurized???
 
it was a stock radiator from a later model cherokee, but I never flow tested it, either it crossed my mind or I drank to much coors light at time of install. :cheers:
 
You mention that it's OK driving, but gets hot at idle. I'll assume your electric fan is working properly. Do you have the shroud on the mechanical fan, and is the clutch operating properly? The shroud is important, as it makes sure the fan's motion isn't wasted.
 
You mention ZJ fan clutch. I don't know about ZJs (6cyl. and/or V8), but 4.0 XJ fans (and their clutches) spin backwards due to the way the serpentine belt is routed. Sorry if I'm barking up the wrong tree, but it may be another idea to chase....
 
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