New overheating problem 87, 4.0, XJ

This may be a little premature, but my 87 Wagoneer, which has run, with A/C flawlessly for several years at 180-195 F, has acted up twice now. Parked the last 2 weeks while I changed the harmonic balancer. 3 weeks ago it blew off the lower radiator hose on the freeway and overheated. Then it drove fine for about a week, but I did not drive it for a long 1 hr highway trip like I did today. Today it ran fine on the highway, with AC on, with ambient at about 90 F. About 3-5 minutes off the freeway, I pull over to look at grand Cherokee for sale, left mine running with AC on for about 2 minutes at the most, then finished my trip, about 5 minutes at about 40 mph, with 4 stop lights. After looking at the grand C I noticed mine was about 10 degrees hotter than normal on the dash gauge, so I pulled the hood and did some checking and found it running hot. The plastic bottle was swollen. IR gauge said the coolant leaving the thermostat housing was at 220 F. Return from the radiator was at 200 F. Electric fan ran for 15 minutes even after turning the AC off. The return coolant tank on the radiator never got back under 180 F.

I tried disconnecting the EGR, at the EGR solenoid, checked the intake manifold temp with the IR and it was 200 F! The EGR was about 180 to 200 F max.

It has a new harmonic balancer and a new gator serpentine belt.

More details in a few hours.

Does it have air in the system sometimes its kinda hard to get all the air out. I am guessing its the closed system since its an 87. Not too familiar with that my XJ is a 97 with an open system.

Change the bottle and burp the system well . get the system back in the "sealed" condition. Also check the fan clutch sounds to me as if its not working.
Lastly.... quit looking at Grand Cherokee's if makes the XJ's jealous lol lol

xj4life2 said:

Lastly.... quit looking at Grand Cherokee's if makes the XJ's jealous lol lol

Click to expand...

HAHA! :roflmao:

xj4life2 said:

Change the bottle and burp the system well . get the system back in the "sealed" condition. Also check the fan clutch sounds to me as if its not working.
Lastly.... quit looking at Grand Cherokee's if makes the XJ's jealous lol lol

Click to expand...

Bottle is not the problem, yet. It barely has 7,000 miles, 9 months on a light duty jeep. It's temporary appearance today was an indication to me that the XJ was running much hotter than normal for mine.

Fan clutch seems to be OK, as I can park it, and idle it for 30 minutes or more, with or with out the AC on, no problem. Clutch is about 4 years old.

What ever is going on seems to be intermittent so far, which makes diagnosis much more interesting.

FlexdXJ said:

Does it have air in the system sometimes its kinda hard to get all the air out. I am guessing its the closed system since its an 87. Not too familiar with that my XJ is a 97 with an open system.

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I have never had the notorious air trapped in the block system problem, unlike many others here.

Yes it is the 87 stock, closed system.

xj4life2 said:

Change the bottle and burp the system well . get the system back in the "sealed" condition. Also check the fan clutch sounds to me as if its not working.
Lastly.... quit looking at Grand Cherokee's if makes the XJ's jealous lol lol

Click to expand...

So you think my XJ got the hots for that cool looking Grand Cherokee? :dunno:

The system is still sealed, at least not any visible external leaks, in fact it may be too tightly sealed ( I have a worm gear clamp on the bottle cap, but that should not stop the cap from venting at 16 PSI).

Your fan clutch can have numerous problems, and 5 years is about max life for the fan clutch and water pump.

Your fan clutch should be hard to turn when the engine is dead cold, this is because the silicone fluid leaks out of the reservoir when it sits and cools down, so the viscous coupling is engaged.

After starting the engine the silicone fluid will return to the reservoir and then the fan clutch will only engage again when the temperature of the air flowing through the radiator and reaching the bi-metal spring on the front of the clutch exceeds 170 degrees, which is about 20-30 less than the coolant temperature.

Before starting the engine in the morning check the fan clutch, it should be engaged within a one rotation.

Warm the engine to operating temperature, then shut it off and check the fan clutch, it should be even more engaged, just plain hard to turn.

Update time. I drove it back across town just before 5 pm rush hour, 45 minute drive, ran between 60 mph and a few minutes of bumper to bumper traffic, twice late in the trip . Did not run the AC. Never got over about 190 F this time, definately not over 195 F. First 10 minutes it held at 180-185 F. A sign I passed at 4:30 pm said it was 93 F, and very sunny, hot outside.

I pulled in for an oil change once I was back on my side of town. It was 1 quart low. Note that hot idle oil pressure was about 29 psi before the oil change, but was 20 psi earlier when it was trying to overheat. There is a big 10 psi drop in oil pressure in mine between 180 F oil and 200 F to 210 F oil.

Also, the electric fan was not running when I stopped for the oil change, so the coolant leaving the radiator was under 170 F (Based on prior extensive thermal switch tests I have run on my setup) after the second 45 minute trip (AC off). Also, the closed system coolant poly bottle looked normal again, not bloated.

Next is the gas mileage. It is noticeably higher (like 25 to 30% higher, even with the AC running and some driveway idling this tank of gas), a record high for my city driving for this XJ, and I have a 4-5 year history on this XJ. So it must be running leaner.

Also I have never seen my intake manifold at 200 F, or even 185 F before!

The engine runs smooth.

Oh, for what it's worth, the brake vacuum booster has a significant leak, that pushes the idle to 1000 rpm, if my foot is on the brake. If I switch to neutral, and take my foot of the brake peddle it runs at 700 rpm. Vacuum leak is only during braking.

One thing I forgot to mention was that the earlier overheating today, just before I turned it off, I disconnected the EGR vacuum line for about 2 minutes, but nothing changed. Then I gunned the engine in park a few times, and then it cooled down about 20 degrees (in just 2 minutes), from 220 F to 200 F at the thermostat housing, and from 200 to about 180/170 at the return side of the radiator (outlet tank side).

OH, and the exhaust system is only about 12-16 months old, new muffler and new Cat, and exhaust pipe. EGR is about 4 years old, about 30,000 miles on it. No changes in acceleration or power, no coolant in oil or Tranny fluid. Coolant is only 4 weeks old. Replaced with 50/50 mix, old green formula (silicate based) and DI water.

I was concerned that the thermostat might have stuck 4 weeks ago when the radiator hose blew off, but it ran fine for a good 200 miles since then, until today. So I have wondered about it again. For now I am ruling it out as both fans were running, and if the thermostat was stuck partly closed, or obstructed, the return flow from the radiator would have been much, much cooler due to a slower flow through the radiator. In this case it was 220 F in 200 F out when it was running hot, and 3 hours later (return trip) it was 170 F coming out of the radiator, and the electric fan was off! So that also rules out any significant problem with the radiator.

I am thinking EGR leaking, stuck, or EGR solenoid, or O2 sensor biased to running engine too lean (intermittent contamination?), or the beginnings of a head gasket leak, or a sticking intake valve?

Hmm, time to add some MMO. I just added injector cleaner too.

joe_peters said:

Your fan clutch can have numerous problems, and 5 years is about max life for the fan clutch and water pump.

Your fan clutch should be hard to turn when the engine is dead cold, this is because the silicone fluid leaks out of the reservoir when it sits and cools down, so the viscous coupling is engaged.

After starting the engine the silicone fluid will return to the reservoir and then the fan clutch will only engage again when the temperature of the air flowing through the radiator and reaching the bi-metal spring on the front of the clutch exceeds 170 degrees, which is about 20-30 less than the coolant temperature.

Before starting the engine in the morning check the fan clutch, it should be engaged within a one rotation.

Warm the engine to operating temperature, then shut it off and check the fan clutch, it should be even more engaged, just plain hard to turn.

Click to expand...

Nice description and detail, thanks.

Read my last post which rules out the fan clutch. I have no doubt mine is running a few (maybe 3 F) degrees hotter than when the fan clutch was new, but it is not the problem here, as was seeing a 40 F jump today. If it was the problem, the electric fan would have kicked in at the end (Parked) of my return trip when I parked it and left it running with the hood up.

How did you address the "bupring" problem with RENIX - do you drill the thermostat as I do? That won't cause any trouble with op temps (it hasn't for me - on anything I've done it with, including forklifts and generators,) but it does solve the air pocket problem handily.

Concur that 4-5 years seems to be about it for the service life of a fan clutch in the XJ. Probably due to the "elevated" operating temperatures (I'm used to 180-190*F) and the underhood environments, as well as the duty we usually put our rigs to.

The hose clamp shouldn't cause any differences in the venting of the cap - that's internal, and doesn't have anything to do with the threads anyhow. It vents through the interruptions in the male threads - and that shouldn't be compressed beyond utility by the worm clamp.

It does sound as though you're running leaner - which should elevate combustion temperatures as well. I think it would be instructive to find out why (start with the usual suspects - IAT/MAP/HEGO/CTS, in that order, and go from there.)

5-90 said:

How did you address the "bupring" problem with RENIX - do you drill the thermostat as I do? That won't cause any trouble with op temps (it hasn't for me - on anything I've done it with, including forklifts and generators,) but it does solve the air pocket problem handily.

Concur that 4-5 years seems to be about it for the service life of a fan clutch in the XJ. Probably due to the "elevated" operating temperatures (I'm used to 180-190*F) and the underhood environments, as well as the duty we usually put our rigs to.

The hose clamp shouldn't cause any differences in the venting of the cap - that's internal, and doesn't have anything to do with the threads anyhow. It vents through the interruptions in the male threads - and that shouldn't be compressed beyond utility by the worm clamp.

It does sound as though you're running leaner - which should elevate combustion temperatures as well. I think it would be instructive to find out why (start with the usual suspects - IAT/MAP/HEGO/CTS, in that order, and go from there.)

Click to expand...

I have always just removed the right side heater hose at the thermostat housing and filled the poly bottle until coolant exits the thermostat housing, and reattached the heater hose. Then I run the engine up to temp (thermostat opens), run it for 5 minutes, let it cool overnight, then top off the bottle the next morning. It has never failed me on the Renix.

IAT problems does not fit the symptoms at all.

I need to check the HEGO sensor wiring, as I might have disturbed it changing the harmonic balancer. Last time I did that the Exhaust manifold ate the EGO wiring harness leads, in which case the two resent cooling systems failures would be unrelated.

MAP and CTS will get added to my list, but have doubts of their probability.

I am still wondering about head or valve problems. I have had a noisy valve train for 45,000 miles and 4 years.

Ecomike said:

I have always just removed the right side heater hose at the thermostat housing and filled the poly bottle until coolant exits the thermostat housing, and reattached the heater hose. Then I run the engine up to temp (thermostat opens), run it for 5 minutes, let it cool overnight, then top off the bottle the next morning. It has never failed me on the Renix.

IAT problems does not fit the symptoms at all.

I need to check the HEGO sensor wiring, as I might have disturbed it changing the harmonic balancer. Last time I did that the Exhaust manifold ate the EGO wiring harness leads, in which case the two resent cooling systems failures would be unrelated.

MAP and CTS will get added to my list, but have doubts of their probability.

I am still wondering about head or valve problems. I have had a noisy valve train for 45,000 miles and 4 years.

Click to expand...

IAT - not IAC. Bear in mind that the IAT (Intake Air Temperature sensor) has a key role in figuring initial fuel trim, as does the MAP and CTS (the TPS to a lesser degree.)) The HEGO simply provides a feedback loop to make sure the rest of the sensors are doing what they're supposed to do.

The top radiator hose can be an indicator of what the thermostat is doing and how open your radiator is (partially plugged). If the thermostat is sticking, it can make the top hose soft, if the radiator is partially plugged it can make the top hose really hard (depending on how stopped up the radiator is). If the thermostat is sticking, you'd probably notice some pretty wild swings in your temperature gage.
My best guess is maybe trapped air, after you get up to temperature squeeze the top hose, two hands flatten it, then let it refill and flatten it again. Watch the football, often if there is air trapped in the top hose you can see it in the football when you squeeze the top hose a few times.
When I did my head gasket, what tipped me off was the bubbles and foam in the football, also the smell of exhaust when I removed the cap.
The last time I had what you describe, it was a combination of a partially plugged radiator, a marginal fan clutch, bad O2 sensor and a couple of pin hole leaks.
An indicator of the health of your valves and possible head gasket is comparing your plugs. Do a run someplace at around 2000 RPM, pull the plugs warm and compare. If your able do a compression test at the same time, compare your compression with your plug color.
Start with the simple stuff first. When my O2 sensor was going, it almost always showed up in the mid range first, cruising RPM around 2200.
Hard to do with the heat shield in place (another good reason to take it off and throw it away), but the IR on the header at each cylinder may tip you off to trouble, if you get one cylinder with noticeably higher or lower temps it's likely trouble.. I still have my trusty thermistor, surface temperature thermometer, a little slower than IR but works well.
I've seen the top hose so tight it thumped when you tapped it with your finger, I don't remember ever seeing a bottom hose blow. Though I have seen them so old the layers in the hose separate, which can't be good.

5-90 said:

IAT - not IAC. Bear in mind that the IAT (Intake Air Temperature sensor) has a key role in figuring initial fuel trim, as does the MAP and CTS (the TPS to a lesser degree.)) The HEGO simply provides a feedback loop to make sure the rest of the sensors are doing what they're supposed to do.

Click to expand...

Thanks, Don't have my glasses on right on, I probably read IA and moved on thinking IAC, LOL. My IAT, MAT and HEGO are not very old, 1-2 years old. Never have replaced the CTS. I like 8Muds suggestion of using the IR near all the intake ports on the intake manifold.

8Mud, I decided the lower hose failure was a combination of an unusually thick new lower hose, and a thin ridge on the new plastic tank nipple, and my not over tightening the worm gear clamp 3-4 years ago when I installed the new radiator and hoses for fear of crushing the plastic nipple. I recall thinking I could tighten the clamp later if it ever leaked. Never expected it to blow off 4 years later with no warning. As the hose aged, it thinned under the clamp, until the hose was thin enough to clear the short ridge on the nipple. I re-clamped the same hose 4 weeks ago with a new clamp, and it held fine today, but when it got too hot earlier today the hoses were rock hard!

The lower radiator hose blow off, did get the engine up to 260 F (dash gauge reading, final) with no coolant left, as it all leaked out by the time I got to shut it down. I was concerned about the head, but then it ran fine for a week, and 200 miles.

5-90,

How about the EGR for a source of running too lean?

I just discovered the vacuum connector had come loose, off of the EGR valve?

I found no other electric or vacuum line issues, no burned HEGO sensor wires, but that EGR vacuum line being disconnected adds to the leaking brake vacuum booster leak (which I have had for about 3-4 months, so it is not an issue by itself, in fact it was hurting my gas mileage).
I forget the "how & when" details of the EGR valve operation, but I know you remember it all it to well! :cheers:

Ecomike said:

5-90,

How about the EGR for a source of running too lean?

I just discovered the vacuum connector had come loose, off of the EGR valve?

I found no other electric or vacuum line issues, no burned HEGO sensor wires, but that EGR vacuum line being disconnected adds to the leaking brake vacuum booster leak (which I have had for about 3-4 months, so it is not an issue by itself, in fact it was hurting my gas mileage).
I forget the "how & when" details of the EGR valve operation, but I know you remember it all it to well! :cheers:

Click to expand...

Answered your PM already - you can copypasta if you feel you need to.

OK, we have some REAL interesting data here for many reasons!

The HEGO (Heated Exhaust Gas Oxygen Sensor) is running between 0.2 and 0.9 volts, mostly at 0.8 volts at idle, 0.6 volts at 2000 RPM steady, and 0.2 V during decel back to idle for about 10 to 15 seconds! This is a Renix system and it should be running near 2.45 Volts!

So the ECU thinks it is running rich and is trying to compensate by running it lean out to max setting for lean on a Renix!

I will test this by disconnecting the HEGO tomorrow in another test to see if she runs cooler.

I also need to test for the 5 volt feed voltage to verify that I still have 5 volts from the ECU to the HEGO sensor, and test the HEGO heater (power off should be 8 ohms) and heater input voltage, 12 volts.

OK, turns out the data below is wrong.

Had the red probe in the wrong spot on my analog meter. My HEGO is worker, getting 4.99 volts from the ECU to the HEGO sensor, 12 volts to the HEGO heater, & ground is good. It is running just a little bit lean on average (average is about 3 volts, running from 1.4 to 4.4 volts) but is switching back and forth across the 2.45 volt stoich point. It should be averaging 2.5 volts. The swing narrows at higher RPM, but still averages 3 volts (slightly lean).

I am starting to think there may be air under the dash gauge sensor, rear head area. Also thinking I am not getting full flow through the thermostat, but it may just be wishful thinking. Running the heater on the Renix should purge any air from the block, which I have done. But I was readijng 210 to 215 F at the thermostat a while ago and 180 to 185 on the dash gauge.

MY intake manifold seems hotter than normal near the head.

Can anyone pull some IR temperatures for me off their Renix intakes? I am getting 150 to 160 F around the throttle body intake area and EGR area, 180 F on the front intake (Cylinder #1) and as high as 210 to 220 F off the rear intake Cylinder #6 intake port, measuring about 3 inches back from the head, on the unshielded intake port.
Also I am seeing a bout a 10 to 20 degree F rise in the temperature from the rear head near the gauge sensor to the thermostat housing. Is that normal?

Is it due to the water path through the head and block?

Also the MAP is good, 1.4 volts at B at idle, runs up to 3 volts easily on average acceleration, down to 1 volt on decel.

Ecomike said:

OK, we have some REAL interesting data here for many reasons!

The HEGO (Heated Exhaust Gas Oxygen Sensor) is running between 0.2 and 0.9 volts, mostly at 0.8 volts at idle, 0.6 volts at 2000 RPM steady, and 0.2 V during decel back to idle for about 10 to 15 seconds! This is a Renix system and it should be running near 2.45 Volts!

So the ECU thinks it is running rich and is trying to compensate by running it lean out to max setting for lean on a Renix!

I will test this by disconnecting the HEGO tomorrow in another test to see if she runs cooler.

I also need to test for the 5 volt feed voltage to verify that I still have 5 volts from the ECU to the HEGO sensor, and test the HEGO heater (power off should be 8 ohms) and heater input voltage, 12 volts.

Click to expand...

joe_peters said:

Your fan clutch can have numerous problems, and 5 years is about max life for the fan clutch and water pump.

Your fan clutch should be hard to turn when the engine is dead cold, this is because the silicone fluid leaks out of the reservoir when it sits and cools down, so the viscous coupling is engaged.

After starting the engine the silicone fluid will return to the reservoir and then the fan clutch will only engage again when the temperature of the air flowing through the radiator and reaching the bi-metal spring on the front of the clutch exceeds 170 degrees, which is about 20-30 less than the coolant temperature.

Before starting the engine in the morning check the fan clutch, it should be engaged within a one rotation.

Warm the engine to operating temperature, then shut it off and check the fan clutch, it should be even more engaged, just plain hard to turn.

Click to expand...

I checked the fan clutch, and I ran the engine for about 30 minutes, including running the heater to see if it would purge any air from the block, but nothing changed.

After it was all good an hot I turned it off to check the clutch. The best I could do was a 90 degree turn, rotation from start to stop by manually pushing the fan blade as hard I could, to check for clutch resistance. Air flow seems a little low at idle, but more than adequate at 2000 and 3000 RPM.

I am thinking of changing the clutch and thermostat. I am thinking the thermostat may not be opening all the way.

I may pull the dash gauge's temp sensor to see if it has air, but it acts like it always has, making me think the gauge temp sensor area just runs a good 15 degrees cooler than the coolant at the thermostat housing.