Check to see if your bottom hose isn't mashing shut. If the reinforcement goes bad they will suck together and stop coolant flow. When the engins slows down they will open back up some. Had this happen before.

 

First, as I have posted many times before to many others, get rid of that 170 degree thermostat, your doing your fuel mileage and your engines health absolutly no good, THEY ARE DESIGNED TO OPERATE AT 210 degrees. Second, I second checking the lower hose for collapsing, if the wire spring inside goes bad or if when your radiator was replaced it wasn't put in the new hose, you will suffer problems. The lower hose is the suction hose for the water pump, think of it like trying to suck an extra extra thick malt or shake thru a straw, what happens? YOU COLLAPSE THE STRAW AND GET NOTHING

. Same with the lower hose, thats why they put the spring in there in the first place. Then you need to make certain ALL the air is out of the system, loosen, DO NOT REMOVE, just loosen the temp sensor on the drivers side rear of the engine (it's back towards the firewall on the engine) until all the air is out, do so while running thats why you dont remove it, or you'll get sprayed with coolant

Also get a brake line pliers, it's a smooth jaw pliers used for crimping brake lines so you can do brake work and not lose fluid and it dosn't hurt the line just squeezes it shut, use the pliers to squeeze the line that goes to the side of the plastic coolant bottle to stop the flow of coolant, make sure your heater is on defrost, then rev the engine a bit. This forces coolant thru the heater core and by pass line forcing the air out of them. Then clamp off the main line that goes to both the tank and the heater core, it's the line that comes off the T stat housing next to the upper radiator hose, this forces the coolant thru the upper radiator hose helping to force the air out of it EDIT(ALSO DO NOT DO THIS FOR MORE THAN 15-20 SEC. or you may burst your radiator), doing this in conjunction with the temp sensor loosening and you should have 99.9% of the air out of the system. Let us know if this helps ya out.

 

Thanks for the rplies guys! I will do what you suggested Kraby. I have however already checked the lower radiator hose. Sunday I was squeezing both the top and bottom hoses. The bottom felt really stiff, but I will check it again just incase to see if it collapses anywhere. Thanks again, and I'll let ya know how things turn out.

 

Only thing I can add to Kraby's explanation is to rise the rearwheels a bit when you loosen the tempsensor.

Your engine will run a bit hotter with the cone filter setup as the intake air comes from the enginebay instead of the front of the grill. It shouldn't however cause the problem as you described. It only runs hotter when driving slow or idling. Some say the cone setup leans out the mixture a bit, thus rising the engine temp. I doubt it because the FI system is set up with so many sensors to always form the best possible mixture. An adjustable MAP sensor can be a remedie to richen the mixture a bit, but again, it's probably a non noticeble gain temp wise. (But a gain performance wise in combination with the cone filter. But that's another story.)

I'd first do what Kraby advised.

 

Well this is my 2 cents not being very smart at this. I have a 90 XJ that used to have a closed system. I have always run a 195 thermosat and sometimes you have to burp a closed system and I did mine by buying a hose conector at a local parts store that goes in the hose coming from the thermostat housing too the bottle. It has a cap on it to fill or let air out. It is a tee shaped with a hose treads on the top to hook a hose to. Real simple and I like simple I have since put in a open system rad. that if you order one get one for a 91 XJ and it drops right in. I used the bottle for over flow. I got my Rad. at Auto Zone for like $125.00. Hope this helps

 

Thanks again for the rplies fellas. here's my update. yesterday i started looking for the temp. senor that Kraby was talking about. next thing, I started checking the bottom hose to make sure the spring was still good. it felt fine end to end, and no collapsing at all. as I was doing that I got to looking at the back of my radiator. there were some big spots of caked on mud that I must have missed with the high pressure hose (only three times

). anyway, since its such a tight fit and the fans keep water from being sprayed in there, I took the shroud bolts out and push them back so I could get in there with a hose. I sprayed the back of the raditor couple of times for about a total of 30mins. with breaks in between. far as I could tell I got 90% of everthing out of there. put the shourds back together, started the engine up and let it sit for a little while and then took it to the highway. slowly but surely I got up to just a little over 210, and before it would only take about 10 mins. of driving to get it up to 230-240. it toke about 20-25 mins. just to get to a litlle over 210. after driving for a while I let it sit running for a few mins. heat came up a little more, and back to the highway I went and the temp dropped back to normal. After all this I was thinking problem solved, NOT! Was on my way to a buddies house, about 30min. trip at 65mph whole way and back to 230-240 I was again.

I'm still going to try get any air out of the system, but working 6days a week I don't have much time, I'm going to try to get it done tonight after work.

 

Hey B, I don't recall, and your profile lacks the info, does yours have the closed or open system? If it is closed then try this other trick that has worked for me, find a REALLY STEEP ramp, ditch or whatever and drive it on it nose down then rev it a bit, turn it around so it is nose up and rev it a bit, do this a few times checking to make sure the presure bottle or whatever they call it, still has some coolant in it. It does sound like you have some trapped air. Is your radiator still the original? It may be getting cruded up inside if it is, this could cause simialar problem. Also, as a side note to EVERYBODY, you all do realize you SHOULDN'T use tap water in your radiator, supposed to use distilled water just like in a lead acid battery, the minerals in tap water will create a build up much much quicker in your radiators.

 

In reply to:

does yours have the closed or open system?

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In reply to:

Yes, I'm running a closed system too(sucks), hopefully soon to change.

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See the first post, Kraby. But you're right, anyones profile should be complete.

 

In reply to:

Could it be the water pump going bad?

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Not very likely. A bad pump mostly causes overheating at low RPM. About the same counts for the fanclutch. Above 45MPH it's the speed that forces air through the rad. Your engine cools down at slow speed, I think pump and clutch are OK.

 

In reply to:

EVERYBODY, you all do realize you SHOULDN'T use tap water in your radiator, supposed to use distilled water just like in a lead acid battery, the minerals in tap water will create a build up much much quicker in your radiators.

[/ QUOTE ]

Good point indeed Kraby. When I got my radiator flushed the other weekend the guy at the shop told me to start using distilled water. He said he saw some calcium build up in my radiator because of using tap/city water.

In reply to:

Is your radiator still the original?

[/ QUOTE ] The radiator was replaced last Oct., so it's still pretty new. I will try this trick out as well then too Kraby (tonight on my way home). I still have yet to have a chance to try to get the air out. Thursday, no matter what I'll get to it. The engine, as stated before is running cooler in city driving. I'm actually staying under 210 up to a little over 210. It's the 60-65mph that gets me backup around 230-240. Thanks again for the help!! I'll keep ya updated........

 

In reply to:

A bad pump mostly causes overheating at low RPM.

[/ QUOTE ] I never even thought about that NIX, another good point. Course too, the only time I've seen water pumps go bad is when they spray water all over the engine compartment. Then ya know there bad lol

In reply to:

I think pump and clutch are OK

[/ QUOTE ] Defiantly agree with ya there. BTW, just for conversation sake I'm getting rid of my air intake and putting stock back in. I'm going to try, I think it's called a cowl air intake system. I think that's right spelling. This was just talked about in another post not to long ago. This method is suppose to help your engine run a little cooler as well, and keep water/mud out. Hopefully this weekend I can get it done. Thanks for the help NIX!!

 

In reply to:

See the first post, Kraby. But you're right, anyones profile should be complete.

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Doughhhhhhhhhhh

Man I should change my screen name to "need more sleep" or "dead on my feet" LOL, I had read the first post before, but only gave it a quick skim this early morning (was 2 am here

)

 

been there done that, you've seen me in action. lol

 

Alright Kraby, I found a nice steep dirt mound/hil tongiht. Went up frontwards and backwards, put it in park and reved the engine while watching the overflow bottle. It did not budge either time, the fluid level stayed put the whole time. I did notice the the temp starting to rise though until I got back down onto level ground which is normal. Just wondering, what does this eliminate or prove?

 

In reply to:

Just wondering, what does this eliminate or prove?

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The object is to get the air out of the system. By design there are a lot of points in the cooling system at which air gets trapped. In your expierence in life, what do air pockets or bubbles tend to do in a liquid? They rise to the highest point. So by doing that, on a steep enough surface, it would help work the air out of the system, which is one of the things that can cause the overheating symptoms your jeep has expierenced. Suggested it as a "free" possible solution to your problem, did it help? If not, what are you out? Nothing

 

But, reducing and deducing, what causes the overheating?
- It only overheats at higer RPM's, according to the gauge, but also the electric fan kicks in, so the gauge is probably right.
- Pump and clutch seem to be okay as the engine cools down from high temp to normal temp at low RPM.
- This may lead to tinking the rad is also OK. It's also rather new and flushed.
- system seems to be bled properly.
- No visual leaks.
- No mayonaise in oil or oil in coolant

So what causes overheating at higher RPM's?
- engine burns hotter at high RPM's than at idling (= normal)
- cooling system is apparently not able to bring down the engine temp generated at high RPM's.
- temp is raised because the system leaks at rad/pump/cap/block head (gasket from coolant to outside). A pump that pumps well can still leak a bit. Coolant on a hot engine outside vaporises directly.
- temp is higher than normal because of a leaky headgasket or cracked head. Normally oil in the coolant or mayonaise on the dipstick, but not always. Especially since this rig only overheats when really hot, mayonaise won't be made as the water in the oil vaporises immediately. Possibly only really leaks a bit at high RPM's. If direct from a cilinder or exhaust to coolant, oil in coolant can be minimal. So check with a CO tester at the filler in the coolant bottle. More thinking of a cracked head than a blown gasket. crack in intake would cause a white cloud from the exhaustpipe, but probably not the overheating.
- Coolant flow is restricted. Maybe the rad is still a bit clogged up with new old crud. Sufficient cooling capacity for a warm engine, not for a hot engine. Was the block also flushed or only the rad? Maybe a hose collapes. Maybe a hose turns soft at high temps and is folded a bit. Maybea a motormount allows the engine to turn under load. Other possibilities?
- Air flow is restricted. Not very likely.
- airpockets. Mostly a system burps itself at 240. Besides, every trick has been tried. Would this system have a mind of it's own?
- Do you have an auto tranny? Is it slipping and creating lots of heat? The tranny oil is cooled in the radiator and affecting the temp. Forget this if you have a manual.

So in my limited wisdom that leaves 4 causes:
1. leak in the cooling system
2. cracked head
3. restricted coolant flow
4. heat from another source

Now we only have to find out whichone it is....

 

In reply to:

The object is to get the air out of the system.

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Okay, got ya Kraby. Something new learned, and a nice trick at that. Much appreciated

In reply to:

Was the block also flushed or only the rad?

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Yea the block was flushed too.

In reply to:

Do you have an auto tranny?

[/ QUOTE ]
NIX, yes I do have an auto tranny. I should have said that from the beginning. But it is not slipping at all, although I did add another 3/4" of lift with shackles on the rear. I did this just a day before the trail ride. Now I'm starting to wonder if the pinion angle is causing the tranny to work extra hard, therefore leading to more heat than normal. What do you guys think? Like I said before, I'll try Kraby's first method of getting the air out and see what happens after that. This thurs. I will do that, and we'll see from there. This is getting frustrating!!

 

In reply to:

Now I'm starting to wonder if the pinion angle is causing the tranny to work extra hard, therefore leading to more heat than normal. What do you guys think?

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I think it would ruin the U-joints instead of the tranny or cause some vibrations. But you didn't mention them. Carry on, I'm sure you'll discover the cause of the overheating sooner or later....

 

Well a secondary cooler on the tranny is always a good idea. They are about $75 through JC Whitney if I remember right. I wouldn't think 3/4 of an inch would cuse that much trouble but who knows.

 

Now I'm opening a whole new can of worms. I have no shimms installed yet, although I got the SYE. A second tranny cooler would be a smart way to go too. I would think that it would help out a lot with the heat/stress on the tranny. Thanks again to everyone for the help and suggestions!!

 

Read and learn about sye, double joints an pinion angle here .

Maybe start a new thread on this topic?

 

Gentlemen ya'll are fergetting one big clogger,,,the engine block my be the real problem...$$$$ to fix it.

 

Okay guys, one more post. I figured out the problem!
READ ALL THE WAY THROUGH FIRST!!!

I spent a lot of time trying to figure out what was up. Things I've done since I last posted:
-replaced the t-stat for the second time with a new OEM t-stat(WHICH HAS A HOLE IN THE 12:00 POSITION TO HELP BLEED OUT AIR)
-replaced the radiator cap with a OEM one, cause the spring might be bad on the old one
-made sure all the air was out of the system
This still did not sovle my problem! Still was getting almost red-line!

Other considerations (thoughts to myself) I took into account:
1. maybe the wrong motor oil, NO
2. temp. senor bad, NO if it were it would probaly stick at one temp and not move
3. fan clutch bad, maybe so I tested it by holding up a dollar bill to make sure it was sucking air through good, and it was. Plus why would it matter at high way speeds, when I'm getting hot most of the time anyway? I left the old one in!
4. Maybe the transmission is causeing the extra heat. Is my transmission slipping alot, I'm I really having problems with it at all. NO! Can't be the tranny!
5. Could it be the water pump going bad. Possiability! But do I hear a wineing noise from the bearings going bad?, or am I spraying fluid everywhere in my engine compartment from the seal going bad? NO to BOTH! Plus I would be getting hot while city driving anyway and I'm not. So it can't be the water pump!
6. Air intake might be causing this, no. This did not start happening until after the trail ride and I had my set up before that with no probs.
7. Postive I got all the dirt out front and back, checked a million and one times.
8. Could it be my radiator hoses. Both look newer, the bottom has the spring in it. Not likely the cause.
*****What else could it be??????? My last thought before considering something major wrong with my engine that I'm not noticing.
9. Maybe something pinched in the radiator, could be a possiability although only 9 months old!
So I decided to replace the radiator with a Modine from NAPA auto parts. Sat. evening I started in on the replacement and got the old radiator out. AND LOW and be HOLD, this was all happening because of caked MUD in between my condensor and radiator!!!!!

So I decided to go ahead and install the new Modine cuase I've heard really good stories about running them, and kept my old one for a back up. I rinsed out the old one BTW, and seemed like a unlimited amount of mud just kept coming out, and coming out. I diconnected the condensor as well and took it out, and left it out!! I never use my A/C so all it's going to do is trap mud and cause more problems. I bought a new bottom radiator hose as well and put the old spring into it. I also put in a bottle of RED LINE Water Wetter with my Anti-Freeze, which I've also read good things about.
My turn out has been Great!!! I now run under 210 about 90% of the time. It does not get much over 210 at all! Even trail riding last night it started get up around 215-220 range and my fan kicked on and right back down to under 210.

Can't explain how happy I am know!!

I just wanted to let everyone know what happen with my situation. I hope this helps someone out in the future! Thanks again for all the suggestions and help guys.

 

Congrats dude! What a bummer to go through all that and discover it was just dirty! I bet you have a healthy knowledge of the Jeep cooling system now. Happy wheelin dude!

 

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