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heating probs!!!

R

redrockphil

NAXJA Forum User
Location
slc utah
I have a 96 country. No mods, (not for long) but an running into a cooling problem. The car runs consistently hot. Ovet the middle mark. The fan starts at about 3/4 of the way. Then stops, just above the middle mark. This is a consistent thing. Highway, traffic, etc. Just had my coolant flushed, and thats when the problem started. Drives me mad! I figure its the t-stat, but not positive. I've heard of problems with the fan clutch, but would like to hear some opinions first. Thanks!
 
If the problem started when you had the cooling system flushed, the flush picked up crud from the block and got it stuck in the radiator. Remove the radiator and take it to a radiator shop. They can reverse flush it, boil it out and flow test it.
 
Thanks Eagle. I'll definiotely get on that. I thought the t-stat gets screwed up if the temp goes over 220 or so. Should I still replace it?
 
OK. Gettin a little aggrevated. I replaced the T-stat. I fluched the radiator again, this time I asked them to use the acid flush first, then put in the base, the re-flush. Still runnin hot. Gets bad when I sit in traffic, stays about 220 on the highway (70 mph). I have no leaks. The fan clutch was "checked", they said it was OK. Not sure where to go from here. Any help would be appreciated. Also, is it bad to be driving the car? It never hits red. But still runs hot.
 
redrockphil said:
OK. Gettin a little aggrevated. I replaced the T-stat. I fluched the radiator again, this time I asked them to use the acid flush first, then put in the base, the re-flush. Still runnin hot. Gets bad when I sit in traffic, stays about 220 on the highway (70 mph). I have no leaks. The fan clutch was "checked", they said it was OK. Not sure where to go from here. Any help would be appreciated. Also, is it bad to be driving the car? It never hits red. But still runs hot.
Click to expand...

Make sure you actually hitting 220.... I doubt you are.
 
Don't take this as insulting, but I assume you are aware that an XJ with a good cooling system will normally run right about 210 in warmer weather. With an OEM cooling system, that's the DESIGN operating temp.

Given that the guage is not REAL precise, if you are reading anywhere close to 210, I would hazard a guess that it's actually working normally, especially since you have a clean rad, a new thermostat, etc.
 
AZ Jeff said:
Don't take this as insulting, but I assume you are aware that an XJ with a good cooling system will normally run right about 210 in warmer weather. With an OEM cooling system, that's the DESIGN operating temp.

Given that the guage is not REAL precise, if you are reading anywhere close to 210, I would hazard a guess that it's actually working normally, especially since you have a clean rad, a new thermostat, etc.
Click to expand...

my 88 reads one needle width above the 210 mark...after warm up. so it's normal to me. before I slapped my new rad in ( i poked a hole in it being lazy when I changed my fan clutch..:rolleyes: ) it would read just below the red.. but the thing never seemed that hot and it never boiled over or blew the pressure cap... so i doubted my gauge was even correct. I replaced the sending unit still read hot... so I drilled a hole in a junk yard thermostat housing, threaded it, built a little housing for my thermistor on my Digital Mulitemeter.. and it read 208.. even though my gauge was saying it was hot... after the radiator... thermistor read 204... gauge was still off... Put the original thermostat housing back on... and never worried about the temp again.
 
Ringkong, your experimental data supports something I have been saying on this board for a while--guages in automobiles are NOT very accurate, and are only "trend indicators".

There have been numerous discussions about how the fuel guage and speedometer are less than precise, and now you have data to show that, at least in one XJ, the temp guage is no better.

XJ owners (and all car owners, for that matter) would do well to understand that factory guages are not laboratory quality instruments, and trying to get precise measurements from them is delusional.

Use the guages as intended by the manufacturer--as an indication of a trend in fuel level, or temperature, or oil pressure. If the trend indicates something bad is happening, then get another instrument to get a precise reading.
 
As far as I'm concerned NO electrical sending units are accurate unless you are paying big bucks for them and they have been and are calibratable. Quality gauges like stewart warner cost more but are well worth it. Problem with the newer XJ and others are the computer ties in with the senders so you are stuck keeping the stock senders to keep the system happy. Putting in an additonal mechanical oil gauge is easy, just put a 'T' block between the factory sender and hook your mechanical up to the other side. Water temp becomes an issue as so far I have not found a spot for another sender though I like ringkongs method. But where do you mount a fluke :D
 
Does it seem hot?

That flush could have affected the TSU in some way maybe. Try replacing it. Have also heard of really strange problems when the Ph goes really off in a vehicle's cooling system. Maybe that crappy flush is not all out of the system and is throwing things off. Go somewhere that has those Ph stips and take a sampling to see. Also, could be a leaking head gasket....may have been really close to blowing and that corrosive flush pushed it over the edge. -I don't know, i am thinking, throwing out possibilities.
 
If the problem seems to be heating up when stopped, like at a light or in heavy traffic, and the temp returns to "normal" (whatever that is for your truck) when you get moving again, that's the classic symptom of a failing fan clutch. I don't know how they tested it, but both my current dealer AND my brother's best friend, who used to be service manager at the dealership where I bought my '88, have told me that there is no way to accurately test the fan clutch. If it won't cool when not moving but cools down when moving -- replace the fan clutch.
 
I thought a lot about this problem as is really bugs me. I know the needle is not acucrate, so I did consider the fact that itis off. And most certainly it is the trnd that is worrying me. The fact that it heats up while not moving, makes me think it might be the fan clutch. So, the fan clutch is next on the list. The needle goes anywhere from a bit above middle mark, to the red. If it gets too close to red, I just blast the heat and cruise about 45 to cool it down. I'm going to get it acid flushed again, then replace the fan clutch.
Thanks to everyone who replied, your comments have been most helpful. I'll keep you posted.
 
No I did not. I got a second radiator flush, this time with an additional acid pre-flush. Still running hot. I will change the fan clutch in a few days.
 
Update...
Changed to a heavy duty fan clutch, and added a 180 degree t-stat. Ran fine for 10 min, then back to hot temps. Almost to the red. I'll take a look at the sending unit next, and take the radiator to get it tested. Any other ideas?
 
89xj said:
did you change the sending unit on the thermastat housing.
Click to expand...

That one is for the engine controller. There is one just for the gauge on the left side of the head near the firewall.

87-96 use a sensor for the gauge (back of the head).
87-90 use a sensor for the engine controller (engine block)
91-96 use a sensor for the engine controller (t-stat housing).
97-01 use a single sensor for the engine controller which relays this information to the gauge via a data buss (t-stat housing)

I wouldn't rule out a bad sensor especially if it's not boiling over.

Some items to make it over heat a idle/slow speed would be a partially plugged radiator, a aux fan that is not working properly, a bad radiator cap (not holding pressure), and possibly a head gasket (not real common). Probably something else I can't remember.
 
Hmm. I checked the aux fan, and it wont turn on till its almost to the red. Is that right? I thought it should turn on sooner? And what tells the aux fan when to start? The red cap is less then a month old. Got a new one. The head's not leaking. I dont believe its the sending unit since it actually really gets hot. I can actually feel the heat incresing. So, I guess I have to flow test the rad.
 
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