Inklover17
NAXJA Forum User
- Location
- Oklahoma
I have been having an overheating problem and I changed the resevoir and hoses and it still overheats. Is my thermostat out?
-
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Thermostat???
- Thread starter Inklover17
- Start date
CanMan
NAXJA Forum User
- Location
- Lake Tapps, WA
Could be. Its an easy fix to see if thats the culprit.
hanaxj87
NAXJA Forum User
- Location
- Cincinnati,Ohio
Possible thermostat... Also consider
Fan clutch and /or electric fan assy. not working
Water pump
Check and clean raditor
Good Luck
Nick
Fan clutch and /or electric fan assy. not working
Water pump
Check and clean raditor
Good Luck
Nick
scat
NAXJA Forum User
- Location
- Santa Clarita, Cali
I had a similar problem a while back. I had a stock aluminum/plastic radiator that had a leak in the plastic reservoir seam. I never really noticed leak but it would overheat pretty bad. Pressure check is effective for diagnosing this failure mode.
5-90
NAXJA Forum User
- Location
- Hammerspace
Tests before you open things up:
Heat your mechanical fan clutch with a hair dryer, and see if the resistance to turning the fan increases (it should.) If it does not, replace the fan clutch. Typical life seems to be four years or so - when you put the new one in, take a Sharpie pen and write the date on it.
What year? You can usually test the thermal fan switch with a hair dryer as well, if you're patient. Or, let the engine idle and monitor coolant temperature with a non-contact IR thermometer near the TFS (location varies by year. 1987-1990 has it in the driver's side radiator tank, 1991-up has it in the thermostat housing. The ECU triggers the fan relay on 1991-up models, so it can be a bit more involved.) 1987-1990 is a simple thermal switch - it should "close" (zero resistance) up somewhere around 215*F, as I recall. 1991-up units are "thermistors" and will follow a predictable curve as temperature increases. I think I've posted it here before.
You have a pressure leak somewhere, which allows the coolant to boil at a lower temperature (each 1# of pressure in the system increases the boiling point by 3*F.) The 242ci six likes to run ~210*F, water boils at 212*F. Not much room there (antifreeze depresses the freezing point of coolant, but doesn't do much for the boiling point. Tangent - has it been changed in the last two years?)
You may have an "air pocket" behind the thermostat - they can accumulate with time and gradual overheating. If/when you put the new one in, drill two 1/16" or so holes in the flange where they won't be covered by gasket. Install with one hole at 12:00 and the other at 6:00 - that takes care of that.
Your electric fan motor may have failed - easy test. Unplug it, grab your DMM, and check resistance between the two pins. I don't recall what it should be, but it should not be either "zero" (indicating a short) or "infinite" (indicating an open.) Either result indicates necessary replacement.
The electric fan relay may have failed - you'll need a 9V battery and a pair of clip leads for this one. Connect your meter to pin 30 and pin 87 on the relay, you should see infinite resistance (open circuit.) Leave the DMM connected, and connect the battery to pins 85 and 86 on the relay (doesn't matter which is which.) Your DMM should show zero, or close to it. Replace if not. Location of E-fan relay varies year to year.
Grab your non-contact thermometer, let the engine idle, and take readings across the radiator core as it heats up. There should be a definite downward gradient as you move from the passenger side to the driver's side, and it should also decrease slightly as you move downward. If you note any spots that don't heat up or don't cool down, you have a clogged core - and should get it seen to (if a flush doesn't correct it, take it to a radiator shop to have it "rodded out" or replace it outright.)
Heat your mechanical fan clutch with a hair dryer, and see if the resistance to turning the fan increases (it should.) If it does not, replace the fan clutch. Typical life seems to be four years or so - when you put the new one in, take a Sharpie pen and write the date on it.
What year? You can usually test the thermal fan switch with a hair dryer as well, if you're patient. Or, let the engine idle and monitor coolant temperature with a non-contact IR thermometer near the TFS (location varies by year. 1987-1990 has it in the driver's side radiator tank, 1991-up has it in the thermostat housing. The ECU triggers the fan relay on 1991-up models, so it can be a bit more involved.) 1987-1990 is a simple thermal switch - it should "close" (zero resistance) up somewhere around 215*F, as I recall. 1991-up units are "thermistors" and will follow a predictable curve as temperature increases. I think I've posted it here before.
You have a pressure leak somewhere, which allows the coolant to boil at a lower temperature (each 1# of pressure in the system increases the boiling point by 3*F.) The 242ci six likes to run ~210*F, water boils at 212*F. Not much room there (antifreeze depresses the freezing point of coolant, but doesn't do much for the boiling point. Tangent - has it been changed in the last two years?)
You may have an "air pocket" behind the thermostat - they can accumulate with time and gradual overheating. If/when you put the new one in, drill two 1/16" or so holes in the flange where they won't be covered by gasket. Install with one hole at 12:00 and the other at 6:00 - that takes care of that.
Your electric fan motor may have failed - easy test. Unplug it, grab your DMM, and check resistance between the two pins. I don't recall what it should be, but it should not be either "zero" (indicating a short) or "infinite" (indicating an open.) Either result indicates necessary replacement.
The electric fan relay may have failed - you'll need a 9V battery and a pair of clip leads for this one. Connect your meter to pin 30 and pin 87 on the relay, you should see infinite resistance (open circuit.) Leave the DMM connected, and connect the battery to pins 85 and 86 on the relay (doesn't matter which is which.) Your DMM should show zero, or close to it. Replace if not. Location of E-fan relay varies year to year.
Grab your non-contact thermometer, let the engine idle, and take readings across the radiator core as it heats up. There should be a definite downward gradient as you move from the passenger side to the driver's side, and it should also decrease slightly as you move downward. If you note any spots that don't heat up or don't cool down, you have a clogged core - and should get it seen to (if a flush doesn't correct it, take it to a radiator shop to have it "rodded out" or replace it outright.)
DrRandy
NAXJA Forum User
- Location
- B'Ham Alabama
If you do find it to be the Thermo. be sure to change the gasket also. I think mine was a few bucks.
Good luck...should be and easy one to find the prob
Good luck...should be and easy one to find the prob
Mullet Man
NAXJA Forum User
- Location
- Kirkland IL
5-90, lots of good info there, thanks alot for that. i am in the same boat and am in the process of daignosing the cooling system.
5-90
NAXJA Forum User
- Location
- Hammerspace
Amazing what you can pick up over the years, isn't it?:roflmao:
I started doing this sort of thing when I was about six, so I've been at it for a little while. Just tryin' to help.
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
5-90 gives the most accurate, detailed answers that you'll find here (or on any Jeep forum for that matter). He has helped isolate many tough problems.
He is a "student of the game" as it is defined....and obviously very much enjoys the fine art of armchair troubleshooting! :thumbup:
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
X2 :cheers:
Inklover17
NAXJA Forum User
- Location
- Oklahoma
Actually guys I replaced resevoir as stated before changed the thermostat and gasket and it still overheated. So finally I thought maybe I know what is wrong does anyone think they can guess what it was?????? Anyone???? Yeah all it needed was antifreeze! But the resevoir was cracked anyway so it needed to be replaced. Now for tomorrows project I change the o-rings in the oil filter adapter. Any advice?