Another overheating nightmare

[VixJeep]

I hesitate to even begin another post about a Comanche overheating. I've read all the posts I can find here and elsewhere. The problem is that its still overheating. I will give you a little background and what I have tried, then post a couple of questions.

 

This is an 88MJ, 4.0L, SWB 2WD. mileage - around 400,000 miles. It has about 15k miles on a rebuilt motor, and a new radiator was put in at the same time. I have done a pressure check on all cylinders and they are all around 140-150. It ran OK all spring, then started overheating as the weather warmed up this past summer. (Note: I bought this truck new, and have NEVER had an overheating problem). Crank it, 5 minutes later its boiling over.

 

My first purchase was an OEM reservoir and OEM cap, since it was blowing the old one off.  After a few more boil-overs, I removed and replaced the thermostat. I bought the one with the little valve in it, and I put the valve near 12 o'clock. I went with what was recommended for the vehicle - 185 or 190 degrees. (In the past I've used a 165 degree)

 

I realized that my problem was probably trapped air, so I changed the thermostat cover out with a newer model one that had an opening for a sensor in the top. I put a valve in there. (I saw this somewhere, it wasn't my concoction). I parked it nose up, jacked it up a little to get more angle, and bled it from the front. Same result. Five minutes, and it was in the red. I now know the right way to do this.

 

As I was working with it, the water pump started to make a little noise, so I replaced the water pump and the  fan clutch. Until this point, when it got hot, it would leak from somewhere. I had to reposition and super-tighten all hoses, and it still drips a few drops under pressure, but not like it did.

 

I saw a post where someone mentioned the heater valve. That was a new revelation. There was no vacuum hooked up to it, so I held it open with a zip tie, turned the HVAC to warm, fan off, put it nose down, and burped it. ran it, let it cool. repeat.  I've done that 4 times now.

 

I remove the sensor, air comes out, coolant comes out. reinstall sensor, run it, and now it takes about 7 minutes to get to about 235+, and  here's the kicker. When cool, the reservoir is almost full. When I bleed the air out, the reservoir goes down to about 1 inch of fluid. After I run the cycle and let it cool, its at the same place it was before. There is no less air in the system after 4 times burping it. I havent had to add coolant. That confuses me, cause that means the air I burp out comes right back - do I just need to keep on doing this?

 

So, here are my main questions:

 

1) Could the higher temp thermostat be the problem? or, rather, could a lower temp thermo help?

2) I plan on bypassing the heater valve, but until then, could that be the source of my problem?

3) When running it to burp it should the heat actually be blowing, or just in the warm position, fan off?

 

4) I looked at the metal reservoir method, the closed to open system change (with and without radiator replacement).

    I have the Moroso inline filler on order for the top radiator hose, but haven't figured out which reservoir would be best. Has anyone found one that fits well where the reservoir sits? Any tips?

5) My question here is how the heck does the open system work better? How does any fluid in the overflow get pulled back in the system if needed? I'd really like to be able to wrap my head around this. 

6) What have I missed, or where did I go wrong? This almost has to be something "easy" that my ADD just skipped right over.

 

Thanks in advance, guys.

 

[al3x_tayl0r]

I'm no professional on these things but I had a car with a similar issue, I replaced everything and couldn't figure it out, it ended up being a mixture of bad timing and running lean, given that was a carbed big block 460, but just throwing it out there it couldn't hurt to check the timing  :dunno:

[watchamakalit]

Plastic expansion tank cracked?

The cap on the tank is also a pressure cap just like what most people think of when you say radiator cap. Most people don't realize that a cooling system needs to build pressure to be capable of handling the cooling needs of the engine. If it's not holding pressure it will overheat.

 

The same attention needs to be played to the 50/50 mix of antifreeze and water.

[reubj]

Blown head gasket or cracked head?

[87MJTIM]

Blown head gasket or cracked head?

 

I thought that also.  But, he said a compression test came in at 140 - 150.

 

I would look at the reservoir bottle and cap.  On mine, the cap has blown and would not hold pressure.  It could screw down "tight" but leak at pressure.  Purchase the Volvo cap from NAPA.  Another clue is that the bottle fills up when hot.  The anti-freeze is expanding from the engine to escape through any crack.  It may be due to a crack in either one.

 

Good luck.  Let us know what you find.

[cruiser54]

In the meantime, try the 703-1396 Napa cap. If that works/helps, look into eliminating the pressure bottle entirely. I prefer the Moroso conversion.

 

Original radiator?

 

And no, the heater valve won't cause overheating. 

[64 Cheyenne]

Test the coolant with chem test strip to eliminate/confirm  combustion gasses in the cooling system.

[VixJeep]

Alright, I can go with the new NAPA cap for the reservoir. it makes sense that the coolant wouldn't expand as much as it appears to be. Instead, air is escaping with pressure and being drawn back in when it cools. A coolant test isn't a bad idea either. As to the other questions, the radiator was replaced in 2011, but it only has a few thousand miles on it (less then 10,000). The coolant bottle and cap I am using is an OEM from the dealership, and was bought last summer. The darn cap alone was nearly $20.

 

That would be a quick, easy project for tomorrow, but the 2 NAPA's near me don't have it, and we're expecting 5-8 inches of snow tonight and tomorrow. I'll take the lazy way out and order it online. By the time we thaw out, I'll be ready to go.

 

Thanks for all the input. I haven't ruled out anything yet. I'm going to start here and see how it goes.

[VixJeep]

One more item: Cruiser, thanks so much for the tips and tricks. When refreshing my grounds, I found that my negative battery cable is connected to the block on the dipstick bracket bolt. Still gotta fix that. I've done the C101 connectors. Trying to work my way through them all, but a long way from done.  

[cruiser54]

One more item: Cruiser, thanks so much for the tips and tricks. When refreshing my grounds, I found that my negative battery cable is connected to the block on the dipstick bracket bolt. Still gotta fix that. I've done the C101 connectors. Trying to work my way through them all, but a long way from done.  

Great!!

 

Do you have an O'Reilly's around? They can cross the Napa part number.....

[VixJeep]

I got the NAPA 703-1396 cap and tried it this morning. I parked it nose down, removed the sensor at the back, and burped it till it was all fluid. Put the cap on, cranked it up. It took 6 minutes for the temp to get to one notch shy of the red line. It also boiled out at the cap. So, the question is.....just how tight do you get it? You only get a couple of turns till you can feel the gasket contact the neck, and it gets tough to turn. I got about 1/4 turn more, then put both hands on it and turned it a bit more. I guess I need to repeat this in the morning, with the cap tighter. If it gets hot, I already have the Moroso filler neck for the upper hose, and I think I can make the reservoir bottle into an overflow tank. I'm also going to have a closer look at the filler neck. That bottle is new, but its boiled over about 20 times since I got it. 

[HOrnbrod]

How are your radiator hoses? The lower hose likes to collapse under throttle when it gets old and tired effectively shutting off coolant flow, especially if it doesn't have the coil spring inside. Take a peek at it next time it overheats.

[VixJeep]

The lower hose is a new one, and it has the spring in it.

 

I tried it 3 times today. Instead of letting it get so hot, I ran it up to 210 and shut it off.  First time, I detected a little steam escaping from the hose coming off the reservoir. After it cooled, I reworked the clamp and tried again.

Second attempt, I still saw a little steam escaping, same place,  and added a second clamp. It still had some pressure on it when I took the cap off.

Third attempt, I let it get up to about 220 degrees, and the pressure held. Each time, I'm burping air out of it.

 

So it looks like I had a leak(s) in the system, which would explain the overheating. It doesn't appear to be leaking now, but I probably didn't get all the air out of it. I'll burp it a time or two in the morning and see if it will run any cooler. If not, we go to plan B.  

[schardein]

Please don't be offended, just trying to help.  When you installed your new thermostat, the end with the spring went into the block?

 

Can't remember if it can even be put in backward on a Jeep 4.0, but it can on some motors.  I've seen it.

[JCole]

Go to napa and get a combustion gas test kit. It will tell you if you have a blown gasket or cracked head. I'm leaning toward head cracked. Its a cheap kit like 15 or so dollars. Will tell you for certain, its frustrating i know.

[HOrnbrod]

Please don't be offended, just trying to help.  When you installed your new thermostat, the end with the spring went into the block?

 

Can't remember if it can even be put in backward on a Jeep 4.0, but it can on some motors.  I've seen it.

 

Another "Aw s&$t" is the rotation of the water pump. Did you eyeball the new pump's impeller against the old one to make sure they are the same (reverse rotation)? Some Jeep models use the same pump with standard rotation.

 

[schardein]

 

Please don't be offended, just trying to help.  When you installed your new thermostat, the end with the spring went into the block?

 

Can't remember if it can even be put in backward on a Jeep 4.0, but it can on some motors.  I've seen it.

 

Another "Aw s&$t" is the rotation of the water pump. Did you eyeball the new pump's impeller against the old one to make sure they are the same (reverse rotation)? Some Jeep models use the same pump with standard rotation.

 

 

Yep.  I'm sure this doesn't apply here, but I have seen a regular rotation fan (for v belts), installed on a CJ7 with a serpentine (reverse rotation) motor.  CJs with California emissions had serpentine/reverse rotation setups on the old 258.

[cruiser54]

 

 

Please don't be offended, just trying to help.  When you installed your new thermostat, the end with the spring went into the block?

 

Can't remember if it can even be put in backward on a Jeep 4.0, but it can on some motors.  I've seen it.

 

Another "Aw s&$t" is the rotation of the water pump. Did you eyeball the new pump's impeller against the old one to make sure they are the same (reverse rotation)? Some Jeep models use the same pump with standard rotation.

 

 

Yep.  I'm sure this doesn't apply here, but I have seen a regular rotation fan (for v belts), installed on a CJ7 with a serpentine (reverse rotation) motor.  CJs with California emissions had serpentine/reverse rotation setups on the old 258.

 

Got bit by that one once.

[VixJeep]

UPDATE

 

Thanks to everyone that has responded so far. I appreciate ALL input. Something that sounds silly is probably whats going to fix it.

 

Now we're getting somewhere! I bought a BlockChek system at NAPA. It was the only one they had. $43. I ran the test twice, and there is NO emission gas in the coolant!!! Cool. I was beginning to wonder.

 

I also checked my water pump. Its a GMB 110-1080. According to the pictures I found of it, its the right one for the serpentine belt. The thermostat is in there the right way. I made sure of that.

 

I pulled out all the stops today. First, I took the top radiator hose off and filled it there. The radiator was only about 2/3 full. Then I jacked up the front bumper, and burped some air out of the valve I installed in the thermostat housing. I let it down and then jacked up the rear bumper about 18" above the front, and burped it at the sensor. It had a lot of air in it - still. I've repeated that a couple of times, and get the same result. At about 6 minutes, I shut it off around 220 degrees.

 

I thought of a couple of others, too. I checked my bottom radiator hose and made sure that it was getting warm when the thermostat opens. It was warm. And belt routing. I'm pretty sure everything is right, but I haven't found my diagram yet to make sure.

[fiatslug87]

[HOrnbrod]

UPDATE

 

I also checked my water pump. Its a GMB 110-1080. According to the pictures I found of it, its the right one for the serpentine belt.

 

Most of the standard vs. reverse rotation water pump mixups are because the wrong pumps are in a mislabeled box.  It did happen to me once but I caught it by comparing the two vanes before putting it in. The impeller or housing usually has an "R" stamped on it too indicating reverse rotation, but not always. Not saying that's your problem, just don't dismiss it yet.

[Jackrabbit41]

I hesitate to even begin another post about a Comanche overheating. I've read all the posts I can find here and elsewhere. The problem is that its still overheating. I will give you a little background and what I have tried, then post a couple of questions.

 

This is an 88MJ, 4.0L, SWB 2WD. mileage - around 400,000 miles. It has about 15k miles on a rebuilt motor, and a new radiator was put in at the same time. I have done a pressure check on all cylinders and they are all around 140-150. It ran OK all spring, then started overheating as the weather warmed up this past summer. (Note: I bought this truck new, and have NEVER had an overheating problem). Crank it, 5 minutes later its boiling over.

 

My first purchase was an OEM reservoir and OEM cap, since it was blowing the old one off.  After a few more boil-overs, I removed and replaced the thermostat. I bought the one with the little valve in it, and I put the valve near 12 o'clock. I went with what was recommended for the vehicle - 185 or 190 degrees. (In the past I've used a 165 degree)

 

I realized that my problem was probably trapped air, so I changed the thermostat cover out with a newer model one that had an opening for a sensor in the top. I put a valve in there. (I saw this somewhere, it wasn't my concoction). I parked it nose up, jacked it up a little to get more angle, and bled it from the front. Same result. Five minutes, and it was in the red. I now know the right way to do this.

 

As I was working with it, the water pump started to make a little noise, so I replaced the water pump and the  fan clutch. Until this point, when it got hot, it would leak from somewhere. I had to reposition and super-tighten all hoses, and it still drips a few drops under pressure, but not like it did.

 

I saw a post where someone mentioned the heater valve. That was a new revelation. There was no vacuum hooked up to it, so I held it open with a zip tie, turned the HVAC to warm, fan off, put it nose down, and burped it. ran it, let it cool. repeat.  I've done that 4 times now.

 

I remove the sensor, air comes out, coolant comes out. reinstall sensor, run it, and now it takes about 7 minutes to get to about 235+, and  here's the kicker. When cool, the reservoir is almost full. When I bleed the air out, the reservoir goes down to about 1 inch of fluid. After I run the cycle and let it cool, its at the same place it was before. There is no less air in the system after 4 times burping it. I havent had to add coolant. That confuses me, cause that means the air I burp out comes right back - do I just need to keep on doing this?

 

So, here are my main questions:

 

1) Could the higher temp thermostat be the problem? or, rather, could a lower temp thermo help?

2) I plan on bypassing the heater valve, but until then, could that be the source of my problem?

3) When running it to burp it should the heat actually be blowing, or just in the warm position, fan off?

 

4) I looked at the metal reservoir method, the closed to open system change (with and without radiator replacement).

    I have the Moroso inline filler on order for the top radiator hose, but haven't figured out which reservoir would be best. Has anyone found one that fits well where the reservoir sits? Any tips?

5) My question here is how the heck does the open system work better? How does any fluid in the overflow get pulled back in the system if needed? I'd really like to be able to wrap my head around this. 

6) What have I missed, or where did I go wrong? This almost has to be something "easy" that my ADD just skipped right over.

 

Thanks in advance, guys.

Get the macs radiator aluminum tank. I replaced everything in my cooling system and it still overheated until i got the aluminum reservoir. Totally worth it. 

[VixJeep]

SUCCESS!!!!    I kept coming back to air in the system. When I took the upper radiator hose off to fill it yesterday, I noticed that the radiator was only 3/4 full. I wasn't getting ALL of the air out, the air traveled to the engine where it heated and expanded quickly.

 

This morning, I cut the top radiator hose and installed the Moroso 1 1/4" inline filler. It took over a half gallon  of fluid to fill the system up from there. Then I bled it through the sensor at the rear. Cranked it, and at 5 minutes, it was just getting up to 180 degrees. It went on up to 210, then the thermostat opened, and it went back down. I knew I had it then. It leveled off around 210 and ran like it should.

 

I took it for a drive, about 15 minutes or so and everything is good. I celebrated by replacing the idler pulley and installing my new fan shroud.

 

Thanks to everyone that offered suggestions. I couldn't have done it without you. So, now that it runs, I can charge the A/C. The compressor and dryer have been on for months - but there was no point in trying it as long as it overheated.

 

Next major project will either be new paint job or new seats, carpet, headliner. I'm leaning towards paint first.

[87MJTIM]

Sounds like a beer (or 2) is in order!   :banana: