heating probs!!!

[redrockphil]

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!

[dusterboy71]

Auxplugged in?

[Eagle]

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.

[redrockphil]

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?

[HossHoffer]

Always a good idea to replace the t-stat. Make sure you get the oem spec.

[redrockphil]

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.

[RINGKONG]

Originally posted by redrockphil
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.

Make sure you actually hitting 220.... I doubt you are.

[AZ Jeff]

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.

[RINGKONG]

Originally posted by AZ Jeff
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.

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.

[AZ Jeff]

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.

[RichP]

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

[Judd W. VA]

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.

[Eagle]

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.

[redrockphil]

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.

[89xj]

did you change the sending unit on the thermastat housing.

[redrockphil]

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.

[redrockphil]

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?

[MJR]

Originally posted by 89xj
did you change the sending unit on the thermastat housing.

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.

[redrockphil]

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.

[RichP]

Cat plugged ??

[MJR]

Originally posted by redrockphil
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 engine controller turn them on based on the sensor in the t-stat housing (91-01). It normally comes on inbetween the 210 and next mark on the gauge.

[qwickcrx]

This is not the answer to your problem, but it may help anyways since most xj's run fairly hot while doing heavy 4-wheelin. You might also try a Flow Kooler water pump. About $140.00 but doubles flow rate at idle and adds 22% more water pressure inside block keeping engine temps up to 30 deg cooler from idle to 3300 rpm. I also added an aftermarket adjustable thermostat to my secondary fan. I also plan to put a manual switch in so I can run it when I want without turning on the a/c. Some models turn the fan on in the "vent" mode also

[redrockphil]

I would really liketo know how to rig a toggle whitch to the aux fan. As soon as the fan turns on it starts to cool off, but not much.

[Wayne Sihler]

Turbo City makes a kit you can use.Part # 640-115, price around $55.It includes a relay ,a new temp switch and wireing.
I used a brass T-fitting and screwed it and the stock temp sensor in.I also spliced a switch in the wire so I have manual control.
Any time the temp reaches around 215* the aux fan will come on.It has not interfered wth the normal operation of the AC system and worked well when on the trail at Camp Jeep.
I do plan to pull the 3 core GDI rad and replace it with a 2 core Modine rad.
Wayne

[Eagle]

Before you start wasting money on Flow Kooler supposedly high-flow pumps and Turbo City supposedly high-flow thermostat housings -- check your lower radiator hose. The behavior you describe suggests that the internal spring is missing, weak, or too short, allowing the hose to collapse under suction and cut off the flow of water through the radiator and water pump.

This happened to a friend of mine and it drove us nuts for weeks. His ran fine around town, but up on the highway after 15 to 30 minutes it would cook. He'd pull off, let it cool down, then he was good for another 15 to 30 minutes before it cooked again and he'd repeat the process. Turned out he had an after-market lower hose and the spring was much shorter than the OEM design.

[SomeoneKnows]

My neighbor recently had an overheating problem with their 95 4.0L Cherokee. A few months ago they noticed a leak and assumed the radiator failed so they had it replaced with a new one. A couple of weeks ago the overheating returned and they decided to change the water pump. The water pump was bad but the overheating continued. They took the Jeep back to the shop that changed the radiator. Turns out the water pump had started to scrape metal shavings into the cooling system and clogged up their new radiator requiring another one to be re-installed. Last I heard they weren't having any more overheating problems.

[redrockphil]

Metal shavings?. Hmm.. After I read this post I checked my fluids. Turns out there arent shavings, but little particles of metal (I assume metal) floating in the coolant. I think its probably some kind of stop-leak from the prior owner. Could this have caused a severe clog? I flushed the rad twice now, the second time with some kind of acid based pre-flush. I still have yet to get it flow tested. Kind of low on funds now.

[Eagle]

Originally posted by redrockphil
I flushed the rad twice now, the second time with some kind of acid based pre-flush. I still have yet to get it flow tested. Kind of low on funds now.

The problem with those flush compunds is that they go in the coolant and flow in the normal direction. If your system is clogged with physical debris, rather than just a general build-up of scale, a chemical flush won't dislodge it. A radiator shop will reverse flush it to try to knock that stuff loose. If that doesn't work, they remove the tanks and "rod" each core to open it up. Sort of the automotive equivalent of those heart operations where they shove a baloon into your main artery and blow it up to roto-root out the plaque.

[MJR]

Shortly after I bought my XJ (used with 141,000 miles on it) I had to replace the radiator for leaks. I also flushed and flushed the cooling system (a fair amount of rust buildup) It was in for about 6 months and I had driven it to Las Vegas. On the way out it was fine then coming back it was running hot (warmer outside also). I pulled the radiator out and replaced it again because it was partially blocked at the bottom. Then in about 6 months I pulled it out and back flushed it with a hose. I was surprised at what came out. They looked like rocks but were made of rust. I put it back together and later on decided to have it recored with a Craig 3 row core and have a filler neck added to convert to open cooling. While I was there a guy suggested a coolant filter called Gano. I tracked down a local dealer and went to buy one. The one they suggested looked to small for my likes so I got the next bigger one and it took a lot of cramming to get it in. It works good. I cleaned it once at 6 months and it's now about 6 months later. I have attached some pictures from mine and another XJ that had major rust. It is very important to maintain the cooling system but even so I am convinced that the cast iron head and block will still break off small pieces over time. This filter will save me having to replaceor rod out the radiator frequently.

This is what came out of my radiator after pulling it out and back flushing it with a hose.

http://www.fototime.com/A2CEC114EF7F577/standard.jpg

This is what the tubes looked like in the old core. You can see what looks like rocks in them

http://www.fototime.com/0CBD9653EBCA1A9/standard.jpg

This is the coolant filter I installed.

http://www.fototime.com/95279D6D38A1922/standard.jpg

This is what I had trapped in the filter at 6 months.

http://www.fototime.com/B471DA4BDB0D2A0/standard.jpg

This is what is trapped in it right now another 6 months later

http://www.fototime.com/4BB893F1BEDA949/standard.jpg

This is the core from a not properly maintained 96 XJ.

http://www.fototime.com/51D1C9214805B5F/standard.jpg

This is the heater valve from the same 96 XJ. What looks like clay is rust.

http://www.fototime.com/B9FE8AC42344C93/standard.jpg

[redrockphil]

Wow. Well, I got frustrated enough to get a new radiator. I intalled it 2 days ago. Everything's fine now. Thank god. I like that filter though, I'll probably get one. Thanks everyone for all the help.