smusaf60

My Jeep is giving me headaches and I need some guidance. First I was getting an engine code 24 which indicates the TPS. Ended up I had to change the temp sensor to the temp gauge. Problem solved, no check engine light. Now the engine is running at about 230F which it wasn't doing before. If I'm in a drive thru, it's getting hot. Very close to the red zone. I changed the thermostat, temp sensor for the fan and flushed the radiator. Still running hot. The electric fan doesn't seem to come on when the temp get high. Any ideas?

Pelican

Model years vary in their handling of sensors, e-fan management, etc. etc. !?!?

The sender for the temp gauge (in rear of head) has no effect on check engine light or TPS or anything else but the gauge.

Does the e-fan come on with the A/C or when you unplug the temp sensor in the thermostat housing?

tjwalker

1. Always post year/engine. There are significant differences through the years.

2. VERIFY. Use an infrared point and shoot thermometer pointed directly at the thermostat housing of a hot engine. Don't trust the coolant temp gauge on your dash; it may or may not be correct.

3. Flushing of a radiator doesn't guarantee proper performance. So the radiator and also the water pump are still in play. If you change one, change the other. Neither of these parts are that expensive.

4. Don't forget about your fan clutch, radiator cap and fan shroud (is it intact?) The #1 cause of temperature creep at idle (drive through) is a faulty fan clutch.

smusaf60

It's a 92 Cherokee with a 4.0L. I know the temp sensor is not supposed to do anything but send signal to the gauge, but the wire from the sending unit is the same purple/white as the TPS and MAP. Once I changed the sending unit the check engine light stayed off. The e-fan does not come on when I unplug the sending unit on the thermostat housing. I did run a jumper to it and it ran so I know it works. TJ, does the radiator cap really make a difference? And the fan shroud? The shroud is intact by the way.

djb383

Each cooling system component is just as important as the next. The cooling system is a chain made up of links......and u know what they say about weak links.

SBpunk

Start easy. Change out the t-stat. They're cheap and easy to do. While you're doing that flush the cooling system and put some fresh 50/50 in there. I would swap out the lower hose for a ribbed (HA!) universal hose from NAPA. Sometimes when the hoses get old they get flimsy and suck in when the coolant is flowing thru.

Next check the fan clutch. If its doing this while idling or low speeds this could be a problem too. Its 4 bolts to replace it and pretty simple. Just put a ZJ one in mine and it helped out quiet a bit.

If you stomp on the gas and rev the RPMS look at the gauge. Does the temp drop while the RPM's are high? If so water pump is next. This is a little more of a pain but not hard to do. Set aside a day incase you run into issues like leaking gaskets or lost bolts.

Be sure to burp your system after each of these steps. If none of this works get an IR temp gun and check your radiator for cold spots. Then check your engine. Why do this last? Because all the other stuff is routine things an older vehicle needs done anyway. None of it takes long and its not expensive.

SBpunk

Here we go. Found my source of info

http://www.jeepsunlimited.com/forums...d.php?t=364431

nakosd

I am currently battling heat problems after I replaced my head a few weeks ago. Every time ive done anything related to cooling I did a flush of the radiator using one of those garden hose adapters that connects through your heater hose. And even the last time i flushed it, about a week ago i still got dark brown sediment flushing out of the system.

Before I replaced the head I had about the worst crack you could get, coolant got into the oil and and oil got into the coolant. The engine oil looked like coffee. So at this point im almost positive that im still getting old brown crap that was in the system when i still had the cracked head. And the repeated flushing and normal use SHOULD be slowly cleaning it out. I did not bother to directly flush the heater core yet, so im unsure weather the brown crap is coming from that or my Rad.

One tip I would recommend is definitely for the lower radiator hose. Next time you flush/drain your rad, pull the bottom end of the lower hose up and look at the spring inside. The spring can tend to bend inwards creating a smaller circle than the hose itself. This will allow the hose to collapse and significantly block coolant flow from the radiator into the lower block.

Replace the lower hose and also throw those awful spring clamps away. The spring clamps CAN damage the spring inside the hose if you aren't **** about where you place them when you remove the hose. Replace the spring clamps with screw-adjustable hose clamps.

nakosd

Also before you do anything major that does not involve the water pump, you should address the water pump first.

Pull out the e-fan, before you remove the belt, you need to untorque the plate that spins the water pump. after all bolts are loosened, remove the serpentine belt, then remove the plate.

Drain the coolant into some sort of pan or a bucket. Unbolt the water pump from the engine block and remove the two bolts that hold it to the steering fluid reservoir.

Time to inspect the water pump:
1. Are the impeller blades rusted out? If so toss the pump and buy a new one
2. Try turning the impeller blades and holding the pully disc with the other hand. If you can't turn them seperately, then its solid. If you CAN turn the blade seperate to the pulley bracket, toss the pump and buy a new one. An impeller-shaft failure is actually very rare, but it can happen.
3. Try wiggling the pulley-bracket in and out of the pump assembly. If it moves in and out a significant amount, then that's pretty bad and cause leaks and eventually a failure.
4. Was the pump ever leaking from the bearing? If so then that's also a warrant for replacement.

If everything checks out, apply some more grey silicone sealant to the gasket surface on the pump and then reinstall. If you ripped the paper gasket when you removed the pump, i would recommend putting a new one with some grey silicone paste as well.

The pump is absolutely the most important component, second to the radiator.

Radi

2 fuses and a relay in the PDC for the electric fan. Check them.

Verify the temp with a thermometer before you start changing parts. You hadn't changed anything that would cause the XJ to start overheating, but it appeared to be right after changing sensors. A bad replacement sensor would be my first suspect.

smusaf60

I checked what Pelican asked and the e-fan does come on when I unplug the connector from the thermostat housing. It also comes on when I turn on the A/C. I have no idea what this indicates.

djb383

It does not or it does???????? Fan "on" when the connector is unplugged or when a/c compressor engages is normal and factory default.

smusaf60

Fan on when connector unplugged. It does not seem to come on when the coolant temp goes up or it wouldn't get so close to the red zone. The temp gauge indicates it's running at about 240 degrees. I installed a new coolant temp sensor in the thermostat housing and get the same results.

djb383

What cooling system maintenance have u done? Maybe a new rad, water pump and fan clutch?

smusaf60

So far, I have changed the temp sensor to the gauge, the thermostat, coolant sensor in thermostat housing, flushed radiator and new anti-freeze. New upper rad hose. The fan does come on when unplugged and when A/C turned on. I also followed SBpunk's question and idled till hot, stomped it, ran RPM's and the temp did go down.