Road Trip, A Little Hot

[ParadiseMJ]

Not really a NEW topic, but since it appeared out of the blue...I'm going to post it up anyway.

 

I took a little road trip today to pick up a canoe.  Weather here today mid-80's, 120 mile trip one way, mostly highway.  Temp started out at 195F for the first 20 miles, then started creeping up a tad past 210.  Turned on the e-fan.  Temp went a bit past the 210 mark and stayed there the whole time.  I had to go thru some slo n' go traffic which actually cooled it off.  Some info about my rig:

• 88 4.0L
• AW4
• Open cooling converted, couple years ago

 

Coming back, same thing, 195 for 20 miles or so, crept up to 210+, and stayed there.  When I started back up the hill...mild grade...about 10 miles, it then went to about 230, with the e-fan on, in third.

 

Never really gotten hot before So I'm thinking a couple things:

 

• Rad. cap
• May need flushing
• No sign of water pump trouble

Ideas??

[HOrnbrod]

Mine did this when I had a partially clogged cat. Now I don't have a cat. But for you, no-can-do in Cali.

[ParadiseMJ]

That's interesting.  I did smell some hot metal smell...and it seem to plateau out at around 65-68 mph.  It was hard to push it faster than that, which was also unusual.  The canoe only weighs 60 lbs and is a bit more aerodynamic than my MJ,  I'll check that out tomorrow.

 

Yeah, no can do no cat in CA.

[Alexia]

That's interesting.  I did smell some hot metal smell...and it seem to plateau out at around 65-68 mph.  It was hard to push it faster than that, which was also unusual.  The canoe only weighs 60 lbs and is a bit more aerodynamic than my MJ,  I'll check that out tomorrow.

 

Yeah, no can do no cat in CA.

 

I have done everything on my 1997 swap to keep it California legal and it still would probably fail somehow.

 

That hot metal smell is usually the catalytic converter heating up the floor pan if it is clogged.  Hot exhaust almost became the sixth time lighting the MJ on fire.

[cruiser54]

CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION

Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.

 

And FWIW, radiator caps are a maintenance item. I've seen many fail in 2 years or less.

[ComancheKid45]

Just had a similar temp creep issue with my 91 XJ, new Radiator cap and Thermostat took care of it ;)

[87Warrior]

I fought the same issues in my TJ. It would only get hot when on the highway, cruising in 5th, 2500+ RPM. 

 

Replaced parts individually:

- Thermostat

- Radiator Cap

- Flushed the system many times

- Lower Radiator hose

- Water pump

 

.....and it still overheated on the highway.

 

Replaced the radiator and it was as good as new  :doh:

[ParadiseMJ]

I checked the cat today...the old fashinoned way.  Drove around for 20 minutes or so.  Cat was hot, but not HOT! No rattling.  Also it looked really nice & clean a couple months ago when I replaced the muffler.  I'm going to replace the rad cap today and see what happens.  Are all the caps made in Mexico/China/India??

 

 The radiator has less than 2,000 miles on it.  All metal CSF 2 row, coolant still looks good from rad install.

 

Gotta get a vac gauge too.

[randomguy310]

try the thermostat maybe, I run a 180..

[ParadiseMJ]

Work week plan...I'm DD'ing the MJ this week to sort out my running hot issue.  I popped a tranny cooler hose in my other (commuter) car so it sits, while I deal with the Jeep.  I've already changed the oil...Rotella 15-40 + MMO.

Process of elimination: By today, or tomorrow or the end of the week I should have it zero'd in.

 

• Monday: New rad cap...and I bought a new (used from Chevy Astro) overflow tank with new hose. No change
• Tuesday: Flush n' fill / t-stat / heater core flush / delete heater control valve. Coolant dirty, but not super bad, no oil or scummy scum in it...it had lost it's "green-ness" though
• Wednesday:
• Thursday:
• Friday:

[ParadiseMJ]

I was very surprised that the rad cap had absolutely no effect.  The old one looked quite old even though I know it's only 2 years (and 1500 miles) old. The seal gasket was wavy, and the hold down tabs looked bent.  So on to flush etc. today.

[Zebvance]

Has no one mentioned that you head gasket could be going?

[Zebvance]

If its overheating at idle or stop and go traffic you have a problem with air flow( fan, fan clutch,) if ur over heating at highway speeds then its got to be a cooling issue ( rad, thermostat, water pump, ect.) also I would not suggest putting a 180 thermostat in. You are covering up you problem with a bandaid if you do that. If they put 195s in from the factory and were designed like that and didn't over heat then why is yours? There is obviously no need do something but a stock thermo because the problem is else where. Keep us updated. And sorry for any typos, this is from a phone.

[HOrnbrod]

I was very surprised that the rad cap had absolutely no effect.  The old one looked quite old even though I know it's only 2 years (and 1500 miles) old. The seal gasket was wavy, and the hold down tabs looked bent.  So on to flush etc. today.

I've never had a new rad cap cause any effect, good or bad.

[ParadiseMJ]

try the thermostat maybe, I run a 180..

A 180 t-stat will not control max temperatures.

 

 

Has no one mentioned that you head gasket could be going?

There is no indication that the head gasket is involved.  No exhaust gas bubbles in coolant, no oil/water co-mingling.  Were talking 10-20 degrees here.  This would be my last resort.

 

 

If its overheating at idle or stop and go traffic you have a problem with air flow( fan, fan clutch,) if ur over heating at highway speeds then its got to be a cooling issue ( rad, thermostat, water pump, ect.) also I would not suggest putting a 180 thermostat in. You are covering up you problem with a bandaid if you do that.

It's not overheating in traffic or creeping while idling...it actually cools off when idling.  The fan clutch is a ZJ HD fan. The e-fan is a 97 10 curved blade fan. There is lots of air flowing.  That part works.

 

...and BTW it is a cooling issue

 

 

Anyhoo, I flushed the system yesterday.  The coolant wasn't too bad, but there was a bit of sediment.  I flushed the heater core separately, and then the whole system altogether.  I also removed the pesky heater control valve for better flow.

 

If that doesn't do it, I'll replace the t-stat today.  After that I'm considering relocating the tranny cooler away from the grill to eliminate some heat flow there.  No air restriction due to crap on outside of radiator, condenser or trans cooler...it's clear there.

 

Thanks fellas.

[ParadiseMJ]

Well, still struggling with this.  So far, with a new cap and flush n'fill I got no results.  Same old creep up the hills.  When the hills  are over and I level out, temp comes right back down.  Could someone explain to me how a marginal t-stat could cause this?  I know a t-stat only costs $10 but I just wanna understand it.

 

 When I start out temp climbs up to just under 210...then, it drops down to ~190 and runs at 70 mph on the flats at 195. So, the t-stat is working (?).  Then when I hit the hills, it slowly creeps up to 220-230 and stays there until I get up riding along the relatively flat ridge and into slower traffic in town, up and down small hills.  Still, going 45-50 in town or stopped at a light, it's right at 195-200.  It's only 82 here today.

 

I don't want to have to throw a bunch of parts/money at this until I KNOW I have to.  The new 50/50 mix coolant is sparkly clean flourescent green, ther are no air pockets in the system, the new oil is perfect amber/clear. Oil pressure is 25-30 or so at hot idle (750 RPM) and ~45-55 at 2400 RPM.  The tranny temp is not going over 180F on the steepest, slowest part of the hill.  Turning the e-fan on does very little to lower the temp (5 degrees or so).  I'm not running the A/C.  The heater core is clean & clear. 

 

My water pump is not weeping, and with the belt off it turns freely without any gravely sounds or side play.  The pump was pushing out a good stong squirt/flow yesterday.  No other pulleys are dragging.  My truck is empty, with a half tank of gas.

 

What I have NOT done yet:

• Replaced the t-stat ... which I'll probably do when the thing cools off this evening. (Especially if someone can explain why I'd need to)
• Cruisers exhaust restriction test
• Shooting an IR gun at the t-stat housing when it's at it's hottest to see if I'm getting a good reading...inside. 
• An actual exhaust gas test in the coolant.
• Compression test

Thanks for any input

[Zebvance]

Well, still struggling with this.  So far, with a new cap and flush n'fill I got no results.  Same old creep up the hills.  When the hills  are over and I level out, temp comes right back down.  Could someone explain to me how a marginal t-stat could cause this?  I know a t-stat only costs $10 but I just wanna understand it.

 

 When I start out temp climbs up to just under 210...then, it drops down to ~190 and runs at 70 mph on the flats at 195. So, the t-stat is working (?).  Then when I hit the hills, it slowly creeps up to 220-230 and stays there until I get up riding along the relatively flat ridge and into slower traffic in town, up and down small hills.  Still, going 45-50 in town or stopped at a light, it's right at 195-200.  It's only 82 here today.

 

I don't want to have to throw a bunch of parts/money at this until I KNOW I have to.  The new 50/50 mix coolant is sparkly clean flourescent green, ther are no air pockets in the system, the new oil is perfect amber/clear. Oil pressure is 25-30 or so at hot idle (750 RPM) and ~45-55 at 2400 RPM.  The tranny temp is not going over 180F on the steepest, slowest part of the hill.  Turning the e-fan on does very little to lower the temp (5 degrees or so).  I'm not running the A/C.  The heater core is clean & clear. 

 

My water pump is not weeping, and with the belt off it turns freely without any gravely sounds or side play.  The pump was pushing out a good stong squirt/flow yesterday.  No other pulleys are dragging.  My truck is empty, with a half tank of gas.

 

What I have NOT done yet:

 

• Replaced the t-stat ... which I'll probably do when the thing cools off this evening. (Especially if someone can explain why I'd need to)
• Cruisers exhaust restriction test
• Shooting an IR gun at the t-stat housing when it's at it's hottest to see if I'm getting a good reading...inside. 
• An actual exhaust gas test in the coolant.
• Compression test

Thanks for any input

 

 

 

Thermostats open and close at the temps they are rated at. When the engine is cold ( under the 195 mark) the thermostat stays closed and recirculates the coolent through the engine until it warms up. When it is above 195, the thermostat will open up and send the coolent through the radiator to cool it down before it goes back through the engine. When they fail they start to stick open or closed. Therefore it could be sticking closed and that's where ur getting the spikes. However if you want to test it. Simply take a cruise without it in and see if anything changes. If it doesn't then put it back in because its not the problem. My gfs dad had probs like you were describing in his ranger and it was the head gasket. It would even spike up and then get cool as u are saying. Which doesn't make since to think it is a head gasket issue if its doing that, but turns out it was.... The only other thing I can think of is air pockets in the system which also make since if your saying it creeps going up hill. Gravity would cause that air pocket to go to the highest spot in the engine which would be thermostat housing. Which in turn would freak out the thermostat. Those are my thoughts. Hope you can find the issue soon. I know it can be a pain, I was dealing with them about 8 months ago. Again sorry for typos, this is coming from a phone.

[ParadiseMJ]

I got a new t-stat.  Took the old one out.  Tested at work in a pot of water, side by side, with a digital thermocouple type thermometer.  They both started opening at 192 and were both fully opened at 201.  They both opened at the same rate and both began closing at the same rate when removed from the water.  Identical t-stats.  So, I'm thinking there is nothing wrong with the old one.  Putting the new one in anyway.

 

I'll see what the gauge does on the way home today. Then it's the IR gun to see how accurate the gauge is.

[ParadiseMJ]

So, when I took the t-stat out I was cleaning the housing and found a hairline crack at the the top of the bottom bolt hole of the housing.  The crack is evident on the outside, it goes all the way across, but the inside of the housing looks fine, no crack.  There was no evidence of leakage, but I'm wondering if it possibly let out enough pressure to not let the system to properly pressurize.  However I don't see how it could let out pressure without leaking coolant. 

 

Anyhoo, I put it all back together and drove home.  Still going over the 210 mark but not by very much.  Going to replace the housing with a spare...or even a new one just for shlitz (I don't like that crack)

[cruiser54]

How old is the radiator?

[ParadiseMJ]

2 yrs old...and less than 2,000 miles.  There was a bit of "sediment" in it when I flushed it.  My XJ had the same sediment (and same CSF 2 row radiator) after it's first flush at about 20K miles.  That radiator (in the XJ) is still going strong with the same cooling set-up. The internals of the 4.0 in the MJ are cleaner than the XJ.

[Akula69]

Did you replace the botom radiator hose, and if so, did you buy one that has the spring insode, or did you remove and re-insert the old spring.

 

I had the exact symptoms you are experienceing, and only by chance stopped when it was overheating and quickly opened the hood to see that the bottom hose I had just replaced was partially closed due to the natural vaccum from the water pump. Could not find a 4.0L hose with the spring, so I ended up purchasing a hose for a Chevy 350cc hose with the new spring, pulling it out, and then threading it into the Jeep hose. (Chevy hose came from NAPA). I ran through all the things you have and would post the topic but cannot locate it now.

 

No problems since.

[ParadiseMJ]

I've always been a non believer in the need for the spring since I was told that Jeep discontinued the replacement hose with the spring (or more clearly...Chrysler stopped making the replacement for a Renix ) but I'm open to doubt that at this point.

 

It would seem to make sense, since it only does it when I'm putting my foot into it to get up the hill.  Does the spring have to be made of anything special (stainless etc.)?  Don't know if I could just pick up a 1.5" spring at the hardware store or I need some specialized deal.

[Akula69]

Understand about 'putting the foot into it'. After going through all the things you have (and more) I realized it was happening when I was on the interstate and accelerating hard.

 

I don't know about stainless, but I suppose it would work. I was able to find several hoses that had "ribbing" on the outside of the hose, but it was not wire just rubber "ridges".

 

When I removed the old hose the spring basically fell apart when I tried to take it out. The Chevy hose's spring looked like galvanized steel and all I did was reach into the water pump end and grab the spring with a pair of vice grips. When twisted clockwise it became smaller, and I was able to pull it out. I lubricated the new hose with water and then threaded it in (from the water pump side). The spring didn't like the bends, so I fashioned a 'puller' from a strong coat hanger and snagged it from the other end to help pull it into place (while still threading it in).

[ParadiseMJ]

Well, all the "stuff" I have done to it, it's running cooler...still getting a little warm by the time I get to the top of the hill.  I'm a bit hesitant to drain the new coolant but I have not looked at what the hose does when it's hot, and I rev it to 3K+ RPM.  If it sucks it closed, even a little bit I'll bite the bullet on the spring. At least I'll know that there is some restriction, and that it could be causing my issue.  Thanks

 

Anybody got a good idea about where to relocate the trans cooler to get it out of the engine cooling equation?  I do have a spare e-fan that I could mount it to.