Oyaji

Because I suspect it was the most recent time that America was manipulated into war under false pretenses.

. At an engineering convention in 1998, I happened to meet a Japanese engineer who had worked for Minoru Yamasaki, the lead architect who designed those towers. He told me those buildings were designed to withstand impact from not 1 but from 2 Boeing 707s, the biggest airliners flying at the time the construction plans were made (back in the mid-1960s, quite similar in size, mass, and fuel capacity to the 767s that hit the towers in 2001). He also told me that the buildings were obsolete before they were first occupied, in part because the fireproofing cladding on the steel skeleton was asbestos. Although superior to other materials at resisting heat, by the time the towers were completed the evidence against asbestos as a health hazard could no longer be denied, and because of the asbestos content in combination with the urban environment, demolition plans were economically prohibitive to implement. . Yes indeed, this date should never be forgotten, but perhaps not for the reasons most generally recognized.

No, I had not heard - but that is news I will pass on with gusto. . I agree that The Pub is the perfect place to kick around this sort of topic, and hope to see more of similar topics here in the future. Whether or not they agree with the majority, all civil comments should be welcome. . I must say, I am impressed by the cogent comments I read here tonight (I especially liked Jimoshel's observations, among others).

I did. The load on the alternator doesn't depend on the alternator RPM, but the load on the alternator sure as hell increases as you increase the amperage draw on the system. A heavy load makes the alternator pulley work a LOT harder. And that's when that minimal contact patch probably won't cut it. Oh. Then maybe Oyaji should have quoted you above, not me. :yes: Shoot - I would have quoted both of you if I could, but I am having difficulty getting the finer points of the forum to work for me. I can't even get paragraphs to space properly without including a period on the blank line between them! Multiple quotes only work for me if the post I quote includes quotes within the post I quoted (in example, see the quotes above). . Don't be so touchy - we are all on the same team, right? Though I am new here, I am rapidly getting to recognize some of the names of the guys who have valuable advice to share. I am sure to be drawing upon it as soon as I have the need. I wish I had Comanche specific knowledge to contribute, but I hope the more general knowledge I do have to offer will prove helpful from time to time. If you hadn't yet noticed, I am stronger in the theoretical than the specific, but I hope that will prove to complement the wealth of knowledge on tap here.

.Reading the above, one thing jumps out at me: that you corrected the speedo for tire size, but you did not mention if you also corrected the speedo for the 3.07 final drive. Remember, the AW4 is expecting a 3.55 final drive, but you still have the 3.07 instead. If left uncorrected, that in itself is a 16% difference in indicated speed versus true ground speed. That may not sound like much, but because aerodynamic drag is proportional to the square of the speed, that means a 34% increase in power needed [1.16^2 = 1.34, or 34%] - and the heat rejection capacity required may be beyond the volume delivery that your water pump provides at your engine RPM at indicated cruise speed of 65-70 mph.

Let me preface this comment by noting that, since your overheating is occurring at an indicated 65-70mph, you could just drive at 55-60 mph instead. It is also worthwhile to consider the increase in true speed (and the additional aerodynamic drag load that comes with it) by driving at an indicated 65-70 mph with a speedometer uncorrected for your bigger tire size. You never did mention if in fact your speedo is corrected for the 31"s you are running, and if your tires are 15% bigger in diameter over stock, your true speed at 70 would actually be 80.5 mph. The additional aerodynamic load alone might be enough to cause overheating at that speed, even before considering additional problems. There are just 2 possible root causes of overheating: failure to reject heat within the original capacity of the cooling system (i.e., a fault in the cooling system), and addition of heat beyond the capacity of a perfectly functioning cooling system to reject (i.e., an overloaded engine). Besides normal wear and tear/breakage degrading the cooling system, but (as you can read below form the list of repairs made) in this case this can be discounted as a cause. I suggest the next place to look are at what has changed from stock, since modifications to a vehicle can result in overheating resulting from either or both of those root causes mentioned above. . I remembered reading that there had been some problems with the AW4 swap, so I went back and dug up the following (items I thought pertinent I highlighted in red - all below are quotes by the original author): . It did overheat, even when it had the BA-10 in it. It also had the 31's. Don't think 31's are a deal breaker for a D44 with 3.07's...but since I won't be doing the Rubicon anytime soon...anyhoo, the AW4 has never been quite right (which I can only attribute to my OWN work) electronically. I still can't get a reading on the TPS. Tried to, drove it, tried, drove, and so on. But still, driving down the highway it seems to do fine. I did all the cooling system swapping before, and it ran a some cooler. My trans cooler is directly in front of the e-fan.. .in front of the radiator. Once it starts climbing, even the e-fan only helps a little. I'll read your thread and see if I missed something, but it sure is frustrating.

Honestly I don't think it is just the tires either - I think it is a combination of tires, 5-speed-to-AW4 swap while retaining 3.07 final drive, (and to add 3 guesses as well) uncorrected speedometer, driving style/high speed driving, and maybe also accessories that add aerodynamic drag (a picture would help). Below follow some of the posts I read here that lead me to this conclusion: . In red underlined text below is a practical definition of lugging: . ParadiseMJ, on 20 Apr 2013 - 22:18, said: 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. . These don't actually define lugging, but are symptomatic of it: . ParadiseMJ, on 24 Apr 2013 - 17:15, said: 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. . ParadiseMJ, on 01 May 2013 - 07:10, said: Goes to 195+ then drops off as the t-stat opens for about 30 seconds. Then it evens out at just under 200 for the level ground freeway trip...driving along at 65-70mph for 20-30 miles, until I get to the hill. When I get about half way up, the gauge starts climbing past 210, 220, 230...til I get to the top. . ParadiseMJ, on 24 Apr 2013 - 17:15, said: It's not overheating in traffic or creeping while idling...it actually cools off when idling. . ParadiseMJ, on 18 Jun 2013 - 14:48, said: Mileage...don't know yet...taking a trip tomorrow, about 200 miles one-way, I'll see how it goes. I was only getting about 15 overall. . ParadiseMJ, on 10 Jul 2013 - 23:27, said: Sooo, took my trip, still overheating under load on hiway. .

Actually, no, belt wrap is not the problem discussed here, expected alternator pulley slippage is. Minimal belt wrap is the potential contributing cause. If that's not a problem ... he's not trying hard enough. I can see how a set of four roof-mounted trail lights, paired with upgraded headlights, and a winch would really tax the alternator, and I don't think that tiny contact patch would be up to the task. . I did take note of your minimum 30% wrap comment - that info was new to me - thank you. But if I ever get around to designing a serpentine belt accessory drive, I'll be sure to dig a bit deeper.

The load on the pulley does not change with regard to alternator RPM, because the voltage regulator determines load regardless of RPM. Therefore whereas high alternator RPM does not help, higher engine RPM would increase linear belt speed and would thereby reduce slippage. What does matter is the size of the contact patch between belt and pulley as well as the linear speed of the belt, and since linear speed of the belt is determined by the driving pulley and not the driven one, alternator RPM is immaterial. In this case a larger alternator pulley would offer a larger contact patch and thus reduce slippage... but then the alternator would be working itself harder to provide the same charge rate at less RPM (thus bad for the alternator). Best case would be to increase the amount of wrap of the belt around the pulley. I agree with Eagle's post above.

With regard to driving habits, you should maybe have a read over some of the hyper-miling guides available on the Internet. The main thing to recognize and compensate for is that every time you accelerate, you burn extra gas to get your vehicle up to speed. That means that every time you slow down, you need to burn more gas later to recover the speed you lost to braking. Learn to read traffic and stop lights far ahead of you and slow down only when you must, and by conserving your momentum you will save gas. Accelerating slowly instead of doing "jack rabbit" acceleration will also save fuel... . I learned good economy driving habits during the oil crises of the 1970s, when gas prices tripled or quadrupled over a week or so. Two good tips I remember from those days were to "avoid the brake pedal as if it were a land mine" (exact quote! :D ) and to drive with shoes off for better feel and finer control of the accelerator pedal. Even when avoiding the brakes as much as possible, changes in speed by indiscriminate use of the throttle will still cost you gas (remember - lifting off the throttle slows you down, just like using the brakes does except you are using "engine braking" instead). Pretend you have an egg you are trying not to break between your right foot and the accelerator pedal, and this problem largely goes away.

I never replace cap and rotor unless I have a misfire problem that demands their replacement - I am cheap that way. :) If you are going to replace them anyway, just make sure they are properly indexed and you'll have no problem. I do this by starting with a known direction of error in orientation, then rotating them in the direction of their indexing notches so I feel them drop into place (this works for both cap and rotor). . Going by what the plugs tell you, your engine is not running rich. That means you need to look elsewhere for improvements. Below follow the areas for improvement I can think of just off the top of my head (there may be more I can't think of at the moment). . If you have a significant fuel leak, it should show up when the engine is running. With it safely parked, start the engine and trace the fuel lines fom tank to engine, looking for any drip, wet spot, and/or odor of gasoline. It should not take long - any significant fuel leak should be obvious. . Next is to consider the things that add to the load that the power of your engine must overcome to move the truck. You stepped up to larger tires without changing your final drive ratio. That puts your engine at slower RPM while it is still expected to provide the same power at a given speed. Practically speaking, that is not significant until you are driving at speeds over 35 (really noticeable at 55+ MPH). The reason is that aerodynamic drag is proportional to the square of the speed. Here is an example: if it takes 4 horsepower to counter aero-drag at 25 MPH, then it would take 4 * 4 = 16 horsepower at 50 MPH... and 16 * 16 = 256 horsepower to sustain 100 MPH. Your engine was designed in the era of the "double nickel" - the 55 MPH speed limit. That means the "sweet spot" for best economy in top gear will be around that speed - but because you changed your tire size, your overall gearing has changed. In order to get back into that sweet spot, you need to re-gear. That would mean stepping up to a numerically higher ratio final drive. Simple proportions will let you calculate your need: assuming stock tire diameter is 27", current tire diameter at 30", and current final drive at 3.07, let X = desired final drive ratio. Then 27 / 30 = 3.07 / X. Solving for X yields 3.41. The nearest available ratio to 3.41 is 3.54 - a little high, but much closer than 3.07, so it should net you an improvement. . Since aerodynamic drag is the biggest consumer of energy you can do anything about, it makes sense to start there in any attempts to improve fuel economy. There are 2 ways to to this: clean up the coefficient of drag for your vehicle, or reduce your driving speed. If fuel economy is important to you, think twice about adding things to your Jeep that increase aero-drag: lift kits, roll bar, lights on the roll bar, extended fender flares, bigger side mirrors - anything that increases the frontal area of your vehicle will add to aero-drag. If you must have these things, keeping your speed down to 50-55 MPH will help your economy a lot. . After aero-drag, look at frictional drag. This includes your mud grip tires that have significantly higher rolling resistance than street tread - if you can get by without them, this will save you gas. Wheel alignment can have a significant effect on frictional drag - if you haven't had it checked, maybe you ought to. Use of synthetic lubricants can significantly reduce friction because they are *supposed* to provide equivalent lubrication with less viscosity. (Less viscosity = less friction.) They are available for the whole drivetrain from engine to transmission to transfer case to final drive... but better check for verification from people with practical experience with your vehicle type before using them: I have heard stories of failures blamed on the indiscriminate use of synthetics, so caveat emptor. If you live in a state that allows it, removal of the catalytic converter will net you at least 1 MPG by reducing exhaust pumping losses; otherwise, a new one and other low-restriction exhaust modifications will help to some (greater or lesser) degree. Probably the best tip in this area (and certainly the cheapest) is to inflate your tires to the maximum, and check their pressure at least weekly. It may ride rougher, but your fuel economy will improve. . Cheapest and best overall tip for last: if fuel economy is really important to you, then work continually on improving your driving habits for best economy. It requires attention, but that attention will not only yield better miles per gallon, it will also extend the life of your vehicle - and maybe by improving your situational awareness will make you a safer driver in the bargain.

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth."

For anyone whose interest was piqued by the mention of the importance of sharp edges on the center electrode, the owner of a shop I worked at in my youth had a racing tip to share, which I pass on here. He used to carefully bend the ground electrode out of the way, drill a shallow hole into the center electrode of his plugs, then carefully bend the ground electrode back and reset the spark gap. This adds significantly to the amount of sharp edge offered to enhance spark (though the removal of material does speed up erosion of the electrode). When I first saw this, I was skeptical of the benefit, just as I was of that of sharp square edges... but in the intervening 35 years everything I have read along with my own practical experience and that of others has borne out the truth of this concept.

One fella mentioned Comet scouring powder, another soap, but the best product is belt dressing - just spray it on the grip side of the belt while the engine is running. . With regard to bearings. while you have the belt off you may as well check every driven pulley (including idler) for high drag. Regarding belt tension, it wouldn't hurt to double-check tension measurement after running the engine (to ensure that tension is distributed along the whole length of the belt). I know that as long as there is no slippage, minimal belt tension extends bearing and belt life, but I've been surprised at how much tension it takes to stop a serpentine belt from slipping and squealing.

Dropping a gear costs nothing at all to try, and addresses an issue that no one here has yet commented on. . If the issue of lugging is not well understood, once again I reiterate my advice to go google up some info from engine manufacturers who doubtless do a better job of explaining it than I have done. . I have read all posted here by both the original poster and all contributors in both his overheating threads, multiple times. The fellow with the overheating problem is running out (has run out) of alternatives to try, having already been through great expense trying out things from all helpful readers. I wish him all success in his ventures to solve his problem.

Do I even need to explain here "who cares"? Some people drive other vehicles than Comanches, doubtless many (most? all?) readers here do too - and many of those vehicles DO have aluminum heads. Some people offer brand allegiance blindly - but in the case of zinc plating, that blind allegiance might have costly consequences for users of Champion plugs when they find themselves installing helicoils to replace stripped spark plug threads in their aluminum heads. Mention of a potential problem just might save some folks here some grief, so I threw that in in hopes of being helpful. . Incidentally, I have always had good experience with Champions in old engines with cast iron heads (especially 50+year-old farm equipment), but there is no material difference between how they are made compared to any other copper-cored spark plug (besides the potentially troublesome zinc plating, that is). I grew to like NGKs because my Japanese motorcycles ran well with them, and Bosch because my VWs, Porsches, and Jeeps ran well with them... but all I use in all my old engines are copper-cored plugs with standard electrodes, regardless of the plug maker.

One caveat about Champion spark plugs: do not use them in aluminum heads!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! . The simple reason is that, since they are plated with zinc, and since zinc alloys with aluminum, they will bind to threads in an aluminum head as if soldered. This is particularly troublesome in air-cooled engines because their head temperatures can run as high as 600 degrees, which makes the binding/"soldering" worse. When the plugs are next removed, the threads sometimes come right out with them! For that reason I recommend NGK or Bosch plugs, which are not zinc plated. . I agree about using the same type spark plug as originally came in the engine. Perhaps the reason I suffered with platinum plugs used with old ignition systems is that platinum plugs came out with modern high-energy ignition systems, and that the older systems deliver insufficient voltage for them. Can anyone check me on that?

Since you are insistent that you have a coolant flow problem (and you may well be on the right track there), here is one more thing for you to consider: by being geared over 30% too tall, your water pump is spinning 30% slower too. This results in reduced coolant flow - perhaps reduced MUCH more than 30% (because hydrodynamic flow is not linear in response to change in pump RPM.). . I cannot stress how much a favor you might be doing yourself to simply try dropping down a gear for all your driving. Remember, the AW4 you installed to replace your 5-speed manual was paired originally with 3.54 final drive - yet you kept the 3.07s... and then jumped to 33" tires too! [correction: reading back in the other thread I see you jumped ~15% to 31" tires, not 33" - in combination with a 16% change by keeping the 3.07s instead of compensating for the AW4's 3.54 ratio, for an overall change of ~31%.] Not only are you overloading the engine by demanding the same (or more) power normally delivered when it is running ~30% faster, you are also asking it to cool itself with reduced flow at the same time. . At least on the way to the radiator shop, drive there using one gear lower. If you note normal running results, you'll have the chance to save yourself some money... money you could put toward new ring and pinion sets!

Earlier, I made mention about the desirability of sharp square edges on spark plug center electrodes. Here are a couple pertinent lines from an article by a spark plug manufacturer on the subject: . In addition, electrons are emitted where the electrical field strength is greatest. This is from wherever the radius of curvature of the surface is smallest, for example, from a sharp point or edge. It would be easiest to pull electrons from a pointed electrode but a pointed electrode would erode after only a few seconds. Instead, the electrons emit from the sharp edges of the end of the electrode and as these edges erode, the spark becomes weaker and less reliable. . The article makes a good case for iridium-tipped plugs (maybe I should give them a try - but I had very poor performance with old ignition systems and platinum electrode plugs and have been leery of hype ever since). You can read the whole article here: http://www.thumpertalk.com/topic/886615-takai-rtype-spark-plugs-series-i-ii/.

Well, not a formula, but a method: distance divided by time, for instance "miles per hour". You will need an exactly known distance, a stopwatch, and a very steady foot on the accelerator pedal. Best is flat country where roads are in a N/S-E/W grid pattern - that way you can have confidence in the distance measurement (mile markers are NOT trustworthy in my experience, but country roads in the flatlands are very regularly spaced, often with crossroads exactly 1 mile apart). As long as the distance is known exactly, you will be fine - curves tend to cancel out (left handers are slightly longer distance, rights slightly less, but there are usually about as many lefts as rights - and if you average in your return trip too, any error will cancel out), but hills can make it hard to hold a steady speed. . I suggest a distance of at least 10 miles to provide a long enough sample for accuracy (the farther the known distance, the better), and a double-check on the return trip. You can check your odometer for accuracy in measuring distance., and then take that distance, divide it by elapsed time, and convert it to MPH. Just make sure you are at your intended test speed when you enter your test run and that your start/stop times are accurate, or you cannot have confidence in your measurements when you are done. . With regard to the cause of the smell of unburned gasoline in the exhaust, a bad oxygen sensor could be the cause... But before fiddling with it, why not pull your spark plugs and read what they tell you first? It is easier to read your plugs than test the O2 sensor, ain't it? . I am a believer in reading spark plugs with the seasons (and any time trouble is suspected) and adjusting their gaps and squaring off the center electrodes with a file while they are out (note that I won't have platinum electrode plugs in my engines - I just use regular Bosch or NGK plugs - I have had much better results with them). You can keep tabs on the condition of any changes in how your engine is running that way (cylinder by cylinder - and if you install an underhood remote starter switch you can easily check compression while the plugs are out if you make the time - don't forget to log the results, too!), and keeping the electrodes square-topped and the gaps in spec reduces misfire. (Would you believe that even an engine that is properly tuned and is running well still misses fire about 3% of the time?)

But the main questions are still unanswered. When you were "blasting up the highway at 60-70" "when it was overheating", had you dropped a gear (moved the shifter to the "Drive 2" position) or were you blasting along in top gear/overdrive? Is your speedometer corrected to show your true speed - or is it uncorrected and reading low? And what is your RPM at corrected/true cruise speed of ~65mph?. . Remember in your other overheating thread when I asked you to try dropping down a gear? I meant not to use top gear/overdrive at all, and just to drop down a gear all the time you are driving from now on until when you get around to regearing, to help make up for the estimated ~30% gear change you have done by fitting oversize tires and stepping up to the AW4 (which in stock gearing uses a 3.55 final drive) while retaining the 3.07 final drive ratio. Aren't you running 33" tires? I reckon you should be running at least 4.10 final drive ratio - maybe 4.56 if you are running aggressive tread tires (rolling resistance much increased) and a lift kit (aerodynamic drag load increased). Are you also running a light bar or roll bar with add-on lights? Maybe also bigger mirrors for trailer towing? Extra-wide fender flares? All those things will add to aerodynamic drag too - and your engine cannot be expected to deliver power on tap at any RPM to satisfy the additional load. You are asking your engine to deliver more power at less RPM - and that is probably lugging it and causing it to overheat. . One comment on the water pump - are you running 50/50 water/antifreeze mix or just straight water at the present time? The surface rust/rust deposits look odd to me, as if you are maybe running straight water until you get your cooling problem sorted out. If so, I don't think it is a big deal (though running straight water long-term might be, simply because of corrosion concerns).

That temperature sensor to which you refer - it is the one for the fuel injection, isn't it? If that was a problem and it was causing you to run too lean, you would know it from reading the sparkplugs - so that sensor is eliminated as the cause of your problem. Ditto for pretty much anything resulting from your engine's running condition: going by the plugs, all is well there... . How about your fuel economy? You haven't mentioned that yet. . Nor did you yet mention if you had tried dropping down a gear, nor your results from the simple test for lugging I mentioned before.

Indeed - thermometer in the radiator to calibrate/verify dash temp gauge may solve everything! . Reading back, one further clue I just noticed:

Any chance that some time in the past you forgot piece of rag/sponge/paper towel somewhere in the cooling system? Because some sort of mechanical blockage is about the only thing that comes to mind after all the work you have done so far. You must be exasperated. . You said you had 2 weeks of cool running before this problem resurfaced yet again. To verify - did you try dropping down a gear to make up for the swap to AW4 transmission along with stepping up to oversize tires while retaining the stock 3.07 final drive? . Finally - have you had a look at your sparkplugs? How do they compare to the pictures in this chart? . http://3.bp.blogspot.com/-s_xxuAIEOpI/UY05gi55M1I/AAAAAAAAA_k/TGWSnNiGEaM/s640/Spark+Plug+Reading.jpg

Roger - thank you. . But was that sediment you removed causing an overheating problem, or were you just being diligent in keeping your cooling system maximally clean?.