Replaced water pump...now overheating

heres the details:
1987 203k miles
stock except for the following:
converted the cooling system to this to eliminate the coolant bottle:


even has a over flow tank:


and its got a 3 row radiator.

so ive been running this system for a while now, with no problems at all.
so for a while ive been hearing a slight noise which sounded like a water pump going out. well recently the sound got louder, and my dad agreed that it sounded like a water pump so yesterday we decided to replace it. so it take everything apart, drain the system, go get the new water pump, then put it all back together. so i fill it back up with coolant, then started it up. it was immediately noticed that the sound was still there, so apparently it wasnt the water pump....weird....while idling we were going around checking for leaks, and could not find any. well we happened to look at the temp gauge and noticed that it was warming up quite quickly. soon enough it got about 210 degrees so we shut it off. so we let it cool off for a little bit and decided to drive it a little to see if things changed. so i took a quick drive around the block, and when i pulled in the driveway it was about to hit 260* so i quickly shut it off. saw steam so we popped the hood and found coolant coming out of the cap as seen in picture 1, and the overflow tank almost full of what looked like plain water...as opposed to coolant. What the hell? we replace a water pump and now it over heats? its got recently replaced hoses and a recent flush, so that shouldnt be the problem, and while we had the rad out we flushed it out, so that shouldnt be a problem either. one thing i did notice was that the aux electric fan did NOT come on at all. the sensor was recently replaced and it worked before the water pump replacement. and yes we made sure both the fan and sensor were plugged in.

So my dad and i are stumped. it over heats after replacing a water pump and now the noise we thought was a water pump is actually something else. what could this be? we took a stethoscope and listened to all the pulleys on the serpentine belt and none sounded bad.

any ideas????

The XJ 4.0 engine uses a reverse rotation water pump. If you were given a standard-rotation pump, as used on some other vehicles with the 4.0, then you will not get fluid movement that is needed. Something to check- Try googling the part number for the water pump, or ask the vendor.

ah that kinda makes sense that it could be the wrong rotation pump. my dad took the old pump with him when he got the new one so we assumed it was the right one. i'll check the part number anyway to see if it checks out. thanks!

Check if there is an R stamped on the impeller of the old one. If so it is a reverse rotation pump.

I believe some years of XJ use different pumps, forget which, I know not all 4.0s use the same pump because different vehicles (XJ, TJ, ZJ, WJ, etc) have different accessory belt layouts. Make sure you get the pump with the correct rotation for the year of the accessory brackets and layout you have, which is most likely the same as that of the vehicle itself (so '87 in your case.)

EDIT: also, your overflow tank line has a kink in it right by the tank. I'm not sure if your tank is proper, either - does that barb have a hose inside it that goes down to the bottom of the tank or does it just pour into the top? If the latter, that will probably explain part of why you are overheating as well, the overflow hose needs to be able to suck up coolant when the coolant in the main loop contracts otherwise it will suck up air and reduce the cooling ability of the system.

that clear line is the air line so coolant can flow in/out of the tank. the line to the home made radiator cap is a black line that goes in thru the bottom of the overflow tank.

well i checked the PN on napa's catalog. they gave us 42004 which on the catalog says "Jeep; cherokee; L6 4.0; 01-87" and there is another one on the catalog that says "Jeep; cherokee; L6 90-87" which is PN 24002. im guessing 24002 is what i need and they gave us the other one because it fell in the listed year range. i also looked at the old pump and it does have an R on it, so it is reverse, but through the PN i couldnt find anywhere that said if the new one was reverse or not.

You need to read the description more in depth....

There is a difference between the 42002 and 42004 according to the NAPA website.

The 42002 has a 3.72" hub height with 2.65" hub OD and reverse rotation and the 42004 has a 2.31" hub height with a 3.33" hub OD with standard rotation.

Return the 42004... and get the 42002.

yea i guess i did miss the details... well that explains the overheating then! now to figure out what is causing that weird noise that sounded like a water pump dieing...

:eyes: Look at the pump impeller blade orientation. New impeller blade orientation has to match the old ones. Simple as that.:exclamati

Replaced the water pump over the weekend on a 97 - old one was leaking. Got the pump from NAPA, and while installing it, saw the R stamped on the impeller. Had no idea what it was there for - now i do.

As kastein said, the hose to the overflow needs to attach to the bottom or have a standpipe through the tank to the bottom. That tank does not. I've used the exact one before, no offense but they're kind of chintzy and an upgrade would be appropriate.

The return hose needs to go below the coolant level so the engine can siphon the tank down and keep the radiator full when the system cools.

interesting find....
pulled the new water pump to compare with the old....they look exactly the same!!!!





the old water pump does have R stamped on it, its just too hard to see in the picture. the new water pump does not, yet they both look identical. what the hell? part # suggest i need the 42002 pump... but the 42004 pump is exactly the same as the old one.... am i missing something here?

You might need to bring it over this weekend and I will by source of elimination help you figure it out.

When you went with the three row rad, you lost the hook up for the aux fan. There are a few ways around this, I just use a switch.

However, with a short drive it shouldn't of gone to 260. I assume that you've alreday checked the thermostat.

When you turn on the a/c does the aux fan go on?

Once it warms up, turn it off and check and see if there is resistance on the clutch fan that would indicate that it is working when warm.

I also converted from a "closed" system to an "open" one, I did it differently that you, there is always the possibility that you have some air in the system that wasn't bleed out.

This Friday I will be out wheeling but Saturday afternoon I'll be home in my shop. Let me know,

Thanks,
Fred
Explorer 1

To determine where your noise is coming from take the serpentine belt off and start it up and see if the noise goes away if its still there then its coming from the motor not the accessories/water pump.Only start it briefly though......

Mechanic's stethoscope is a great tool--for some things. When hunting a noise I will pull the metal probe off the vinyl tubing, or just use a 3' section of tubing by itself and hunt around the engine compartment to locate the source of a noise.

outlander said:

To determine where your noise is coming from take the serpentine belt off and start it up and see if the noise goes away if its still there then its coming from the motor not the accessories/water pump.Only start it briefly though......

Click to expand...

will be trying that tomorrow. never thought about doing that, thanks for the idea! and it makes sense because we tried all the other accessories off the serpentine and nothing made any unusual sounds.

joe_peters said:

Mechanic's stethoscope is a great tool--for some things. When hunting a noise I will pull the metal probe off the vinyl tubing, or just use a 3' section of tubing by itself and hunt around the engine compartment to locate the source of a noise.

Click to expand...

yep. thats what i used to check all the bearings. it works great!

Explorer 1 said:

You might need to bring it over this weekend and I will by source of elimination help you figure it out.

When you went with the three row rad, you lost the hook up for the aux fan. There are a few ways around this, I just use a switch.

However, with a short drive it shouldn't of gone to 260. I assume that you've alreday checked the thermostat.

When you turn on the a/c does the aux fan go on?

Once it warms up, turn it off and check and see if there is resistance on the clutch fan that would indicate that it is working when warm.

I also converted from a "closed" system to an "open" one, I did it differently that you, there is always the possibility that you have some air in the system that wasn't bleed out.

This Friday I will be out wheeling but Saturday afternoon I'll be home in my shop. Let me know,

Thanks,
Fred
Explorer 1

Click to expand...

Thanks Fred! my dad and i will be trying things throughout the week so if all else fails we will be bringing the XJ to your place.

But i'll start out by addressing what you posted.

1. with the 3 row rad we got we did not lose the hookup for the fan, it still had it. we did find out that the reason the fan wasnt going on was because of a bad relay. it is getting replaced so now it should kick on at the appropriate temp.

2. i agree! the short drive shouldn't have caused it to got THAT high. and you're right we did confirm that the t-stat was working.

3. yes it does....well when the bad relay was working it did. it still should when we put in the new relay.

4. we will check the clutch fan like you said, just to be sure its still working.

5. you're right i think their could be air in the system as well.




thanks everyone for all your help!

well we did what outlander said and sure enough it made the noise! so does that mean its the timing chain making the noise or could it be something else?

Does it kinda sound like marbles rolling around in a coffee can?
Since you have eliminated accessory noise grab your stethoscope and put it on the timing cover,valve cover,injectors(they make alot of noise that can be confused for something major)I also suggest doing a vacuum test to see how the valve train is doing....

You could be suffering from the infamous 4.0 cracked exhaust manifold.....or loose flexplate bolts.All of the above are good places to start.

nope...its the timing chain. took the cover off and found that it was rubbing on a wear pad on the cover. felt the chain and its definatley loose. will be replacing it tomorrow. that should solve our noise problem.

Good news.
I wish I was as good at diagnosing noises in real life than over the internet....hahaha.
While you're in there be sure not to lose the little spring and pin that fits inside the end of the cam that keeps the cam from walking out into the cover(dont ask me how I know...lol)