Road Trip, A Little Hot

[Zebvance]

Could the timing be off?  - - Sounds like the cooling system's been gone through - - maybe time to look elsewhere

:hmm:

That's what I was just thinks. Bad timing will cause overheating. But as I recall timing is non adjustable on the renix correct?

[ParadiseMJ]

Yes.  Non adjustable.

 

Way back 3 years ago I had a dizzy "whirr" so I replaced the dizzy.  Took me 3 stabs to get it indexed right and as far as the engine goes...it runs smooth, idles at ~750-800 rpm. smoothly.  I also replaced the harmonic balancer.

 

...and I agree that it may be time to start looking at OTHER systems, but how would timing make it run hot ??

[danbyrambler]

Not enuff advance is a combustion duration & exhaust valve thing - power & mpg will be down besides elevated temp - not your symptoms - - - - Too much timing can cause heat to build cause of higher cylinder pressure esp under a load like towing or going up long grades - - Too much is usually accompanied by pinging/detonation but not always, esp when it's just approaching whatever you wanna call that fine line between max allow & too much - -  I used to run my stuff on the ragged edge of + advance back when you could pull over, grab the dist easily & a little +r- & so on - - only temp issue I recall was a triumph spitfire that ran warm when cruising at 70+  - -  Anyway, I'm far from a renix expert - just sayin' - & normally stay away from the shotgun approach BUT, another thing that'll cause hot is a lean fuel mix - If you're right there at the threshold it'll run hot under load & cool down otherwise - spark plugs'll look ok & no pinging - - I've run into this with weber DF/DG carbs which can b adjusted 8 ways from Sunday(2Vs with 4jets each) Lotsa frustration my 1st go round - thought I had a cracked head  - - - - Maybe something for the more knowledgeable CC folks to weigh in on.

:hmm:

[cruiser54]

Paradise: Check your dizzy indexing.

 

 

Remove the distributor cap and cut a "window" into the side of the distributor cap at the #1 spark plug wire post . The "window" should be large enough to allow easy visual inspection of the position of the distributor rotor at the #1 spark plug wire post. Reinstall the distributor cap.

Install a ¾” wrench or socket onto the vibration damper retaining bolt. Rotate the engine in a clockwise direction until the #1 cylinder is at top dead center. Align the timing mark on the vibration damper with the "0" degree mark on the front cover timing scale. The tip of the distributor rotor should be near the #1 spark plug wire post.

Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor.

Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw.

Remove any burrs and metal filings from the distributor. Reinstall rotor.

If necessary, using a flat blade screwdriver, turn the oil pump gear drive shaft until the slot is slightly past the 11 o'clock position. The oil pump gear drive shaft is accessible through the distributor mounting bore in the engine block.

Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole.

Turn the rotor to the 4 o'clock position.
Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o'clock position.

Reinstall the distributor cap with the cutout "window". Rotate the distributor housing until the trailing edge of the distributor rotor tip is just departing from the #1 spark plug wire post terminal .

Reinstall the distributor holddown clamp and bolt.. Reinspect the position of the rotor to the #1 spark plug wire post to insure that it has not moved.

Install the new distributor cap, reconnect the distributor electrical connections.

Revised 07/03/2012

 

Need pics, check out the link in my signature.

[ParadiseMJ]

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

Well, CRAP

 

I had thought I did not have a head gasket issue, but TODAY I went to the dump, hauling my trailer full of junk.  It's all downhill from here so it was running right at temp, about 195.  Then I left there and went to Home Depot, got a load of fence boards.  Left there and headed up the hill...about 7 miles.   Halfway up it started getting hot, and climbed up just before the line before red line, even with the e-fan on.  So, I pulled over, the overflow tank was just bubbling away and overflowing coolant (I have an open system, so it's not a pressure bottle.

 

So, I said...Well, CRAP, or something like that !!

 

Is there ANY other reason that my cooling system would be pressurized enough to spew coolant past the cap??  There is no oil in water or vice versa, so I'm thinking that the head gasket is the culprit and I have a small leak from a cylinder into a coolant gallery...does that sound about right??

[Zebvance]

That was my thought to begin with. Have you tired a pressure test on the head to make sure there is no head gasket leaks?

[cruiser54]

Double check the cap.

[ParadiseMJ]

OK, so I went and "rented" a cap/cooling system pressure tester.  Here's my results:

 

The cap test:

 

The adapter looks the same on both ends, but with it on one way the pressure holds steady for 2-3 minutes.  When I flip it around the pressure drops about 1-2 psi per 30 seconds.  So, one way the cap looks fine, the other way it's bad, but both ends look the same and measure the same from lip to sealing surface.  I'm confused.  Looks like the cap is marginal anyway.

 

The system test:

 

With the engine off, it holds 18 lbs pressure...for over an hour.  With the engine on, idling the pressure slowly rises (about 5 minutes) along with the temp gauge...I assume that's normal.  With the engine at temp and at 2K rpm the pressure rises to 20-25 psi, before I turn it off, then it holds that pressure and gradually decrease as it cools.

 

The instructions say that a vibrating needle indicates a compression leak...no vibrating.  But the fact that it's building to over 20 psi at speed worries me a bit.

 

Is there something that jumps out at you?  Is the rising pressure (up and over 20 psi) an indication of a small, seeping compression leak?  Or is that normal, if the cap farts a little as you're cruising along does that keep the pressure at a normal rate, or does that just build up so much that I'd make the cap just "let go"?

 

I'd really hate to pull it all apart an replace the head gasket or worse, just to find out everything is OK to begin with...how is the head gasket/head definitively ruled out as an issue??

[87manche1]

Pressure test the cylinders with air. And do it that way but could get mixed readings threw blow by of the rings.

[1989 Eliminator]

Maybe some of the channels inside the engine are plugged? Try taking out the coolent plug on the exhaust side of the engine and letting all the coolent and gunk drain out?

[ParadiseMJ]

The engine internals are squeaky clean.  System has been flushed including the block drain twice in the last 6 mos. Coolant is bright green and clear. Oil that is 2 months old is still a nice clear amber color.

 

I'm just going to throw a new rad cap on it today and see what happens...If it still overheats I'll just  push the%$&*@# thing off our local convenient cliff and collect the insurance. 

 

[Zebvance]

I don't know about your insurance but mine wouldn't give me squat for my

Mj if it got totaled......

[Oyaji]

I'm down to this:

I swapped in an AW4 after the BA-10 gave up the ghost.  So, my gearing is still 3.07's...I'm also running 31" tires.  What I'm thinking is that the engine has to work too hard to move those axles, so it's doggy, and when it's doggy is when it gets hot.

 

 

Should have said this from the start!

 

  

 

AW4 has 3.55 final drive gearing because it is automatic, ie, no driver downshifting required. Driver of a manual knows better than to try to climb a hill/drive under load without downshifting, so  the manual transmission driveline got  a 3.07 final drive - but the automatic they tried to           make idiot-proof and thus it got shorter gearing. If I recall correctly, top gear in both the AX-15 and the AW4 are overdrive, and about the same ratio (~.80 or so), right?

 

 

 

 

Furthermore, by running 31" tires you have compounded the problem. As I recall, last time I did the math for an AW4 to run 32" tires you should be running 4.10 final drive to keep the engine in the "sweet spot" it was designed to run at (peak torque), ie, the same RPM at a given speed  that the factory ratio and tire size would yield.

 

 

 

 

Here is a simple test for you: next time you are under load, mash the accelerator pedal and see if you can accelerate appreciably. If not, you are lugging the engine - and it will get hot if you operate  it for very long in that condition. (I am sure you can find heaps of references that explain lugging from a technical perspective - worth reading if you are interested.)

                       

 

 

 

Another simple test: manually drop down a gear (to the "2" position on the shifter) and see if you can accelerate then. Watch your engine temperature as you drive a few miles - I bet it will be closer to normal.  Until you can get 4.10 final drive gearing, you can either go back to the stock 27" tire diameter, or maybe just drive around in D2.

 

 

 

 

Incidentally, your fuel economy should increase pretty dramatically once you get properly geared for your tire size - driving sensibly on the highway should net you around 20 MPG, which is what you would get with a stock truck gearing and tire size.  

[ParadiseMJ]

It's apart right now, replacing the head gasket, as the 5th ex. gas test found some gases in the coolant.  After I pulled the head I found about 1/4" of coolant in #6.  The leak into the coolant gallery is small, compression is good, no prob. with engine pressure tests (except for the #6 cyl ultimately being wet.

 

I do understand however that I'm under geared for 31's or even the AW4.  I do downshift to 3rd usually when pulling the hill home or anytime I'm towing my little trailer.  I will try those things when I get it put back together and on the road after this weekend.

 

Thanks

[Oyaji]

*sigh*

 

Too bad I didn't find this thread sooner - maybe could have saved you a teardown.

 

Incidentally, the coolant you found atop  #6 piston almost certainly leaked there at the instant you broke loose the head  from the head gasket and block when you took it off.  If you had a blown/leaking head gasket/cracked head, your cooling system would not have held pressure, you would have been losing coolant into #6 all the while, and you may even have noticed steam in the exhaust (the cooling system certainly would have been losing coolant). Since  the head is off now, it would be a good time to  consider a valve job if the head has more than 50,000 miles on it. Valves go bad far sooner than piston rings, and though valves are far more robust than they used to be (like back in the day of leaded gasoline, I am thinking), it still might be worth it simply because you have already done the work of pulling the head already. Lugging the engine raises peak combustion temperature, and higher exhaust temps have a way of eroding the exhaust valve  and seat contact surfaces. It wouldn't hurt to check the valve guides for wear, too, while you have the head off.  But before investing in those repairs, make sure they check the head for cracks! It got hot enough to blow out coolant (right?), and now you might have damage you didn't have before... Maybe it is a good time to consider a remanufactured head? They are often substantially cheaper than having your local machinist do the work.Honestly though, since you were so dlligent in your compression and pressure testing, this may well be overkill unless money is no object for you.    

 

If you haven't done so yet, Google up  a technical article (preferably from an engine manufacturer) on "engine lugging" and have a read - it will provide understanding and incentive  to avoid it in the future! You were absolutely on target with your earlier observation about performance being "doggy" when under load: being geared  ~16% too tall  (3.55 / 3.07 = 1.16) and then making your ratio ~15% taller by running 31" tires instead of the stock 27" diameter (31 / 27 = 1.15) gives an overall ratio 31% too tall, which is about like running a gear and a half too high for your road speed.

 

Until you get properly geared, just make sure to manually downshift and not use the kickdown switch in your AW4 (except  for brief acceleration, for instance when passing another car). Kicking down to passing gear has your engine running near WOT (Wide Open Throttle), which ain't good for extended run time  (like when climbing a hill, or when towing a load) - no, not one bit! I expect that is the very reason that Jeep chose the 3.55 gearing for the AW4 yet went with 3.07 for the 5-speed... You might find you get the results you seek  by just dropping down to "drive 2" - but that makes your AW4 an "AW3", practically speaking. :)

 

Sure hope your headache passes soon - good luck, and be sure to let us know what you found out in the end. 

[Zebvance]

*sigh*

 

Too bad I didn't find this thread sooner - maybe could have saved you a teardown.

 

Incidentally, the coolant you found atop  #6 piston almost certainly leaked there at the instant you broke loose the head  from the head gasket and block when you took it off.  If you had a blown/leaking head gasket/cracked head, your cooling system would not have held pressure, you would have been losing coolant into #6 all the while, and you may even have noticed steam in the exhaust (the cooling system certainly would have been losing coolant). Since  the head is off now, it would be a good time to  consider a valve job if the head has more than 50,000 miles on it. Valves go bad far sooner than piston rings, and though valves are far more robust than they used to be (like back in the day of leaded gasoline, I am thinking), it still might be worth it simply because you have already done the work of pulling the head already. Lugging the engine raises peak combustion temperature, and higher exhaust temps have a way of eroding the exhaust valve  and seat contact surfaces. It wouldn't hurt to check the valve guides for wear, too, while you have the head off.  But before investing in those repairs, make sure they check the head for cracks! It got hot enough to blow out coolant (right?), and now you might have damage you didn't have before... Maybe it is a good time to consider a remanufactured head? They are often substantially cheaper than having your local machinist do the work.Honestly though, since you were so dlligent in your compression and pressure testing, this may well be overkill unless money is no object for you.    

 

If you haven't done so yet, Google up  a technical article (preferably from an engine manufacturer) on "engine lugging" and have a read - it will provide understanding and incentive  to avoid it in the future! You were absolutely on target with your earlier observation about performance being "doggy" when under load: being geared  ~16% too tall  (3.55 / 3.07 = 1.16) and then making your ratio ~15% taller by running 31" tires instead of the stock 27" diameter (31 / 27 = 1.15) gives an overall ratio 31% too tall, which is about like running a gear and a half too high for your road speed.

 

Until you get properly geared, just make sure to manually downshift and not use the kickdown switch in your AW4 (except  for brief acceleration, for instance when passing another car). Kicking down to passing gear has your engine running near WOT (Wide Open Throttle), which ain't good for extended run time  (like when climbing a hill, or when towing a load) - no, not one bit! I expect that is the very reason that Jeep chose the 3.55 gearing for the AW4 yet went with 3.07 for the 5-speed... You might find you get the results you seek  by just dropping down to "drive 2" - but that makes your AW4 an "AW3", practically speaking. :)

 

Sure hope your headache passes soon - good luck, and be sure to let us know what you found out in the end. 

 

 

 

VERY GOOD INFO! :cheers:

[ParadiseMJ]

Thanks for the info. 

 

The machinist said the head and valves looked great. Mag'fluxed, no cracks.  I asked him about the valves he said they looked fine and spec'd out fine. I'll be replacing the valve guide seals and putting it all back together.  My first step when my budget recovers is to put smaller tires, 235's, on it until I can gear it properly.  It seems like alI this has all been a major pain, but I've learned a lot, thanks to all y'all, and the luxury of time (as opposed to money).  I've done a fair bit of wrenching in the past but never really got "inside" of an engine except a Volkswagen 1600 I rebuilt back in the day.  Makes the whole "Jeep Thing" even more interesting.

 

Thanks again, I will definitely report back on this WHEN it's all resolved.

[Oyaji]

Still no resolution?  

[ParadiseMJ]

Almost.

 

The head is done and back on, everything is put back together, exhaust, replaced almost all the vacuum lines and got the A/C fixed as well, cylinder compression increased slightly, from 119,120 average to between 125 and 129 across the board. I'm poking along at it as time and energy permits (I've worked 60+ hours this week and building an 80' fence at home...I'm fried). All it needs is plugs (actually only one plug which I broke) and coolant and I'm good to go...I think.

[Zebvance]

Good to hear. We'll I got my fingers crossed for ya.

[ParadiseMJ]

Done with the head and all...although my first test drive I blew off the bottom hose, dumping all my new coolant. I didn't have the hose clamp all the way around...rookie mistake!! I'm driving it around letting it heat/cool/heat/cool with the system all buttoned up and coolant overflow ebbs and flows as it should. No explosions yet, no stray rags, bolts or nuts left in any pistons.

 

[Oyaji]

Almost.

 

The head is done and back on, everything is put back together, exhaust, replaced almost all the vacuum lines and got the A/C fixed as well, cylinder compression increased slightly, from 119,120 average to between 125 and 129 across the board. I'm poking along at it as time and energy permits (I've worked 60+ hours this week and building an 80' fence at home...I'm fried). All it needs is plugs (actually only one plug which I broke) and coolant and I'm good to go...I think.

Interesting  that the compression ratio increased a bit. Did you have the head planed while it was off? Or maybe the new head gasket is a bit thinner than the previous one? Either would explain CR up a bit across the board from previous readings. Another possibility could be readings taken before and after passage of a cold front: barometer difference from a high of, say, 30.5 inHg dropping to 29 inHg would account for a 4.5% difference between readings, maybe? (PSIG might cancel this but for the CR of ~8:1? I am not sure, reaching a bit here...)

 

Still keen to hear of your results where "the rubber meets the road" though - please keep us updated....

[ParadiseMJ]

At this point, I've taken it on a short drive, intentionally hitting it hard from 1800 ft. to 2400 ft elevation. Only about 8 miles round trip. It did fine BUT my top radiator hose is hard as a rock. It bubbled a bit into the coolant overflow (it's open system) but when I got home and let it cool off it sucked all the coolant that had been expelled out of the cap back in to the rad, as it should.

 

I have a few days off, time for a road trip to she how it does. Just the hard rad hose has me concerned.

 

I also have to add, my first compression test was done bone dry and cold. The newest comp test, the Jeep was warmed up.

[Oyaji]

Hmmm... The radiator hose will only get as hard (from internal pressure) as the pressure relief valve will let it. Dunno what cooling system you have (open or closed), but there has to be a relief valve somewhere. On the open systems, this is in the radiator cap; in a closed system, it is maybe the cap on the pressure tank (I am guessing - I never had one/worked on one). If you think you have too much pressure, better test it to make sure - failure can be either inconvenient or even dangerous (think how scalded you could get while working on a running engine if the weak link broke and sprayed you with superheated steam 265 degrees or hotter!).

.

.

.

[edit: Whoops! You clearly mentioned that your cooling system is of the "open" sort - sorry I missed that. Still, all the info there still applies as written, and may help any future reader with similar concerns.]

[Oyaji]

At this point, I've taken it on a short drive, intentionally hitting it hard from 1800 ft. to 2400 ft elevation. Only about 8 miles round trip. It did fine BUT my top radiator hose is hard as a rock. It bubbled a bit into the coolant overflow (it's open system) but when I got home and let it cool off it sucked all the coolant that had been expelled out of the cap back in to the rad, as it should.

 

I have a few days off, time for a road trip to she how it does. Just the hard rad hose has me concerned.

 

I also have to add, my first compression test was done bone dry and cold. The newest comp test, the Jeep was warmed up.

.

.

Another week has gone by since your last update - any news for us yet?