overheating while idiling

I have a 89 limited. Lately I have noticed that the engine wants to over heat when left idiling for a period of time. When I put in gear and go down the road the thing cools off and the temp goes down. What temp should the fans come on at? Is this a common problem? Possible problems and/or solutions are appreciated?

Thanx

The auxiliary electric fan (if you have one) comes on at either 217 degrees or 190 degrees. Most of the information available on the Internet says 217, but the FSM for 1988 (which is the same as 1989) says 190. Either way, that's not the problem.

Overheating at idle is typically caused by a failed or failing viscous fan clutch on the primary (mechanical) fan. The clutch uses a silicone fluid that apparently degrades over time. Some people recommend replacing the fan clutch every five years. That might be a bit conservative, but the symptoms of heating up when idling and cooling down as soon as the vehicle is moving again are classic symptoms of a failed fan clutch.

What Eagle said. Another thing to look at though is whether you have an auto or manual tranny. Autos will heat up if left in a drive gear while you're sitting at a stoplight or in the drive-thru. Knock it into 'N' while waiting and you may see the temps drop as well.

Yucca-Man said:

What Eagle said. Another thing to look at though is whether you have an auto or manual tranny. Autos will heat up if left in a drive gear while you're sitting at a stoplight or in the drive-thru. Knock it into 'N' while waiting and you may see the temps drop as well.

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A properly functioning cooling system in an XJ should be able to keep operating temps at normal, even when sitting in "Drive" in stop and go traffic for long intervals.

Let's put it this way--the designers INTENDED it to withstand those conditions, as they are pretty normal. What they DON'T factor in is the deterioration of all the components of the system due to age. THAT's when you start seeing overheating.

If you havent messed with anything yet-
plan on replaceing the radiator. A 4.0 rad will last a long time...but not forever. They clog and break seams. As mentioned above, go ahead and replace the vis.clutch fan. It cant hurt. Does your aux fan come on at all? If not, replace the sender for it.

When that fun is over with, consider jumping the relay for the aux fan to a handy switch inside the cab. Whenever you spy the tempeture going up, a quick flick of the switch gives you room to breathe.

my 89 has always overheated in summer going up hills since I got her, untill I put in a relay bypass switch- thats with a new radiator, a new fan clutch, proper burp, and a 160 robert shaw stat. I like the 160- Ive tried the 180 and 190- and made a mistake with a 210....210`s are bad. With the 160, I come up to average temp(almost halfway up an down on Mr gauge) quickly....although you never know about those gauges....liars, all of them.

works for me-always has. other opinions will differ, they always do.

Eagle said:

The auxiliary electric fan (if you have one) comes on at either 217 degrees or 190 degrees. Most of the information available on the Internet says 217, but the FSM for 1988 (which is the same as 1989) says 190. Either way, that's not the problem.

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That FSM must be a typo. If it came on at 190 everybody's fan would be on continuously, as the engine is designed to and usually does run at 210. 217 sounds about right, the one in my '96 comes on when it is slightly above the 210 mark.

The first thing you should try is to clean the radiator - inside and out. Take off your grille and remove any crap that might have built up in the radiator. Then give it a good flush with some flush chemicals.

Eagle said:

The auxiliary electric fan (if you have one) comes on at either 217 degrees or 190 degrees. Most of the information available on the Internet says 217, but the FSM for 1988 (which is the same as 1989) says 190. Either way, that's not the problem.

Overheating at idle is typically caused by a failed or failing viscous fan clutch on the primary (mechanical) fan. The clutch uses a silicone fluid that apparently degrades over time. Some people recommend replacing the fan clutch every five years. That might be a bit conservative, but the symptoms of heating up when idling and cooling down as soon as the vehicle is moving again are classic symptoms of a failed fan clutch.

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That's correct, but another possible problem could be failure of the auxiliary electric fan to kick in at the aforementioned 217*. If the electric fan works when you switch on the A/C but not if the engine overheats, the cause is a faulty coolant temp. sensor (that's the one in the t'stat housing). If the electric fan doesn't work at all, it could either be due to the fan motor itself burning out (you can "hotwire" the fan directly to the positive battery terminal to see if it works) or a faulty fan relay.

I have owned two XJ's and both of them heated up sitting at idle in gear or not. Both of them have aux fans that comes on about 230* and off at 210*. On both of them I changed the fan clutch, thermostat and water pump in addition to adding an external tranny cooler removing it from the radiator. Nothing made a difference. The aux fan would come on while at idling. If the AC is on then the temp would stay below the 210* mark as it would while driving. I have had it with mechanical fans and fan clutch that was marginal at best if the XJ was stationary.

techno1154 said:

I have owned two XJ's and both of them heated up sitting at idle in gear or not. Both of them have aux fans that comes on about 230* and off at 210*. On both of them I changed the fan clutch, thermostat and water pump in addition to adding an external tranny cooler removing it from the radiator. Nothing made a difference. The aux fan would come on while at idling. If the AC is on then the temp would stay below the 210* mark as it would while driving. I have had it with mechanical fans and fan clutch that was marginal at best if the XJ was stationary.

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I really think that the engines cooling systems need a good flushing every 100K-200K or so. My 82 S-10 which is the one I had the most experience with . After driving it over 680.000mi I got to know it pretty well. Having replaced 2 radiators and one water pump. The single biggest gain I ever had was the first time I used that 7 hour prestone cooling systems flush. That flush cleaned that radiator like nothing else I have ever seen before and the coolant that came out after that service call from home to syracuse and back home again, about 7-8 hours, was shocking. I had drained and back flushed the system before putting in the water and flush and it was clear. When I drained it the next day the coolant came out looking like brown sludge and it was thick. My cooling temps came right down, the only thing I can think of is that there we deposits just like in the radiator only on the surfaces of the cooling passages in the engine itself that were causing problems, maybe acting as an insulator of some sort. The S-10 also went thru a fan clutch but that engine had a bit more room in the front so I tried two haydens, one spring loaded that was terrible and then a hydraulic, back then I was in the frame of mind of not wanting to buy OEM stuff and pay OEM prices.
As for total electric fans, not for me, too easy for electrics to fail. With electric and properly working mechanical you have a better failover margin though having a bypass switch I'm beginning to see just might be more prudent than depending on the sensor. Just my .02

Just a quick trick if your electric fan dies in traffic and you can't stop the engine: Have the heater run at full blast. I used to have an 89 Mustang (4cyl) with a bad battery and a dead electric fan. Crossing I-95 through NYC in the middle of August was a lot of fun, but the engine never overheated

Dr. Dyno said:

That's correct, but another possible problem could be failure of the auxiliary electric fan to kick in at the aforementioned 217*. If the electric fan works when you switch on the A/C but not if the engine overheats, the cause is a faulty coolant temp. sensor (that's the one in the t'stat housing). If the electric fan doesn't work at all, it could either be due to the fan motor itself burning out (you can "hotwire" the fan directly to the positive battery terminal to see if it works) or a faulty fan relay.

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Dino, the '89 (and 87, 88 and 90) didn't have a temp sensor in the thermostat housing. The engine temp sensor that feeds date to the ECU is located on the driver's side of the block. The sensor that fires up the aux fan is a simple thermal switch located in the driver's side radiator tank.

Eagle said:

Dino, the '89 (and 87, 88 and 90) didn't have a temp sensor in the thermostat housing. The engine temp sensor that feeds date to the ECU is located on the driver's side of the block. The sensor that fires up the aux fan is a simple thermal switch located in the driver's side radiator tank.

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Thanks for that info. Harwood. That's good to know.