• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Radiator Cap question

bigsky

NAXJA Forum User
Location
Victorville, Ca.
Just did the open system conversion on my 89 xj and now it wants to run hotter than before. My question is about the radiator cap.

I got a 16 pound cap from napa but it doesn't seem like my system is getting pressurized. I can squeeze my upper radiator hose with the cap on and watch the coolant level in my overflow tank rise like the bottom seal on the cap isn't even there.

Is this normal or should i just go get a 13 pound cap, the one they list for my new 92 radiator?
 
This thread inspired me to check my cap since I've been getting pretty warm lately. The cap was bad, it would squirt out coolant through the overflow port on the rad if I sqeezed the upper hose. Changed the cap and it no longer did that, but it still gets just as warm. Not sure where to go next, water pump and radiator are pretty new.
 
Radiator caps are getting to be one of those tricky items where you have to get the OEM part to assure decent quality. Even Stant seems to have QC issues. As much as it sucks, try buying a cap from the dealership.(yeah, I know, 'burns my ass to pay 28 bucks for a radiator cap too)
 
ok, got a new cap and now I have pressure. Stil have a little air in the system i guess but I massed with it for an hour last night, today the true test will be when I am coming home from work, I have a nice big long hill on the way home.

Moral of the story is, check your cap. Mine was bas. Everything sold seems to be made super cheap nowadays.
 
So if the cap is bad it usually needs to be burped after you change the cap? Mine almost seems like it has air in the system, the temp fluctuates 5-10 degrees fairly fast. Faster than I think the water temp would be able to change.
 
It does sound like yours has air in the system but the 91+ model years should self burp after a couple of heat/cool cycles.
 
Most parts places have a cap tester that you can use to verify the cap opening pressure (actual). Also need to check the weak spring return seal on the bottom side. The Pressure tester will verify and test both.
 
Well I just got home from work, I watched the temp gauge on the whole way home and she did ooooookkkkaaaayyy but not where I was hoping.

On my initial startup and drive the temp gauge slowly climbs to 210 and then the thermostat opens and it drops to about 160ish or what I would think the 160 area looks like on my gauge. After the first time the thermostat opens and the cycle begins again it just seems like each cycle just gets a little warmer so on and so forth until I am sitting right around 215.

I think there is a possibility that there is air in the system but I burped the heck out of it already. I used a jack and jacked up the front and rear and wiggle and squeezed hoses like a maniac trying to make sure I didn't leave any air in the system.

I am stumped at this point.

There is not one single part of my cooling system that is over 6 months old. Thermostat tests ok in water on the stove.

Any ideas?
 
EcoMike, I replaced the cap and have presuure now. Everything in that department seems to be working just fine. I was also searching and reading some posts that you had written before about looking for exhaust leaks and whatnot.

No exhaust leaks either.

Checked my cat to see if maybe it was the culprit and I did not find any spots that were way hotter than the rest of it. Everything seemed ok. Of course the whole thing was in the 500 degress farenheit range, does that seem abnormally hot for a working cat.
 
i just checked everywhere on my engine with an infrared thermometer. highest temp i found was 170. temp gauge reads 215. it's been idling in the driveway for 20 minutes while i do a coolant system flush, fan has never kicked on (it works). the gauge still reads 215 or so. thermometer still reads 155-170. the gauge/sending unit are not correct.
 
ok went out and checked it again with the IR thermometer most of the head except for the area right above where the exhaust ports are at stay right around 180 right above the exhaust ports it is closer to 250.

So what is a good temp for a catalytic that is not plugged.
 
The actual temp of the sensor on the back of the head is 200

All the IR temps and locations you listed are good numbers.
 
just flushed my system, and i pulled my thermostat which was rusty and looked stuck. got new hoses and thermostat, and a new harmonic balancer since i noticed that was wobbling bad. we'll see how it goes tomorrow when i get it all installed with fresh coolant.
 
Back
Top