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  1. #1

    Jeep Stroker running hot

    I've been chasing this problem for a long time and if I don't sort it out soon I'm going to put a 5.3 in it.

    It's a 4.7 built like the one I wrote this article about.

    http://www.rockcrawler.com/techrepor...er40/index.asp

    It runs hot just about any time the RPM is over 2500 for a sustained period of time. Load doesn't seem to matter much. If I'm cruising around town in 3rd gear (chevy 700R4 auto) it will heat up. If I'm on the highway running 75-80 (RPM will be 2500-2700) it heats up. If I'm climbing up 285 or I70, it really heats up. Today I ran 8-10 miles down the highway at 60 in 3rd and temp climbed to 230. I ran the same stretch in 4th and it ran 212.

    I've got a monster radiator from radiatorexpress.com that's supposed to be good for 350HP. I've got a Derale fan installed in the stock fan shroud with most of the air leaks sealed up so it's drawing as much air through the radiator as possible. I've got a new water pump for an XJ only because I needed the room for the big radiator and fan. New thermostat. New lower hose. 2 speed fan controller from Dakota Digital (low on at 205, high at 210). Today I installed a transmission cooler to relieve some of the heat load from the lower tank. It lowered the transmission temp 40+ degrees and the engine now runs 1-3 degrees cooler under similar situations. I installed poison spyder hood louvers and they seemed to help a bit.

    I altered the transmission lockup system so that it now locks up in 3rd and 4th and I can force it to lock up manually as well. Running it locked in 3rd seems to help a bit due to the torque converter not generating any heat.

    The exhaust system shows no signs of being clogged, but I checked for excessive back pressure and found none.

    I did a compression check today and all cylinders were 150+.

    I'm monitoring the engine temps with a digital autometer gauge with the sensor in the head in the stock location. I welded a bung in the transmission pan so the trans temp sensor is getting the temp from there.

    I'm running out of ideas. I'm toying with the idea of an oil cooler, but I don't want to bandaid it if there is a real problem that I'm not seeing.

    Any ideas???

  2. #2
    Forgot to add, I checked for a head gasket leak with one of those test kits from Napa and no sign of combustion byproduct in the coolant.

  3. #3
    This is a fairly recent development, Right?

    It didn't run hot when you first built it?

    So...what have you added since the build that might have an effect?
    "Your 2007 X3 is at home on all paved and unpaved roads. You can operate your vehicle on uphill and downhill gradients with a maximum slope of 50%. The permitted side tilt is 32%. While driving watch carefully for obstacles such as rocks or holes. Try to avoid these obstacles whenever possible."

  4. #4
    You need to figure out the cause or you'll really be miserable if you throw 5.3 in there and it still runs warm.

    (Could this be jealousy over my 5.9???)

    (OTOH, if you need funds for the 5.3 swap, I'm looking to hire someone to buck some rivets....)

  5. #5
    Lets say I've tolerated it for a while.

    It ran fine for a long time (several years). I swapped in a cheap aluminum radiator off of eBay and that's when I noticed it. I can't say it was the cheap radiator, but that's when I noticed. Since then I bought a Napa radiator that did the same thing, then this big aluminum monster that I have now.

    Full disclosure, I have AC and a warn 9.5TI winch that are mucking up airflow as well.

  6. #6
    My first guess was combustion gas venting into the coolant- sounds like you tested for that.

    Second guess is over lean mixture at load. Plugs look OK when you pulled them for the compression test?

    Third guess is electric fan not moving enough air- either it's defective or insufficient. I had one where the outer ring on the blades had a small crack, and would barely drag against the shroud- ran just slow enough that it wouldn't move enough air at load. It is really difficult to tell if the fan is moving 2750cfm or 1750cfm and therefore causing an overheating problem.

    I was not an electric fan fan (see what I did there?)- until I discovered the Taurus/Volvo fan solution.
    If you cross thread a bolt, there is no need for loctite.

    Run whatcha brung... And hope you brought enough.

  7. #7
    Dumb question- is that water pump standard or reverse rotation, and which way are you driving it?

  8. #8
    I've done a ton of reading and keep thinking I may have located the smoking gun, then I do a test and I'm wrong. I checked the coolant almost hoping it was a head gasket and no luck.

    Plugs were light gray and clean when I pulled them yesterday for the compression test. Jeep passed emissions test in February or March and was running clean then. This problem has been around for at least 2 emissions tests.

    I feel like this fan moves plenty of air. It's a Derale rated at 2,400 CFM. I think Derale is reputable??? I'm getting 30-35 degrees temp drop across the radiator. I ran a taurus fan a while ago, but when this problem presented itself I went back to mechanical with a new fan clutch and still had problems. A mechanical fan will not fit with the current radiator since I've moved the engine forward 1" when I made the motor mount lift.

    I'm pretty sure the water pump is a reverse rotation although I could be wrong. I had to use an XJ pump because the stock one had a longer snout which would hit the electric fan. All XJ's as far as I know used a reverse rotation pump like the YJ with serpentine belts does. I also remember being pretty diligent to check for this problem because I've read about it so many times over the years on the various forums.

  9. #9
    How old is the fan? And have you changed any wiring on it or anything that would cause it to not get full voltage. Just had this problem on my son's Jeepster. He added a switch to his fan because the way it was wired it was on all the time unless cool enough to not be. Even when starting. The way he had it wired it was losing voltage and the fan was not spinning as fast as it used to causing the motor to run too hot with the summer temps.
    CJ/buggy,FI406,465,205,D60,14boltFF on beadlocked 39.50 swampers.See build.
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  10. #10
    God Forgives, Rock's Don't www.ucora.org
    1973 Bronco, 351 SEFI, Locked, discs, 35's ZF-5spd and Atlas 4spd. 235:1 Crawl Ratio

  11. #11
    Quote Originally Posted by cheepin View Post
    How old is the fan? And have you changed any wiring on it or anything that would cause it to not get full voltage. Just had this problem on my son's Jeepster. He added a switch to his fan because the way it was wired it was on all the time unless cool enough to not be. Even when starting. The way he had it wired it was losing voltage and the fan was not spinning as fast as it used to causing the motor to run too hot with the summer temps.
    Interesting idea but I even have the problem at highway speeds when I would think there would be more than enough ram air to cool.

    For some reason the engine is producing more heat than the cooling system can handle. I've read of 3 cases where guys were chasing similar symptoms and ended up swapping the head to fix it. The theory (which I'm struggling to wrap my head around) is cracks in the head that allow more heat in the cooling system than it should. Somehow these cracks allow this, but don't allow oil/coolant/exhaust gases to go where they shouldn't. Not sure I buy it, but I'm running out of ideas. I have another head so I may get it inspected and try it.

  12. #12
    Quote Originally Posted by 74BuckinBronc View Post

    YJs have the open system stock.

  13. #13
    I just noticed that you are running a digital temp gauge.

    Is it actually overheating, or just reading "high" on the temperature gauge? At 240 degrees, with a 12lb cap- it should be boiling into the recovery tank.

    Good quality grounds are imperative for an electrical sender gauge to be "accurate", and even then they are more useful as- "It usually runs around midway on the gauge, and is now running much higher"- I would not trust them to show that the engine is running at the exact temperature the gauge indicates.

  14. #14
    Quote Originally Posted by YJLopes View Post
    Interesting idea but I even have the problem at highway speeds when I would think there would be more than enough ram air to cool.
    Not sure if I missed it or not. But what lb radiator cap are you running? Chasing the heating problem on the Jeepster. We swapped a 15lb in place of the 13lb and noticed it helped it alot. With the 13lb we had 210-215 in let temps and 200 outlet. With the 15lb it's now 190-193 inlet and 180 outlet. Not sure if the 13lb cap was bad or not. And we know the 15lb is good because we stole it off our suburban to test. I have heard of others doing the same and it solving the problem.

  15. #15
    I am confident in the accuracy of the gauge. It matches all of the other indications I have (IR gun/stock gauge). I'm well aware of the necessity of good grounds. Working on high dollar little airplane engine monitors, I've seen all sorts of gremlins trace back to bad grounds.

    It has a 16lb cap, and this is the second one that has been installed on the system.

  16. #16
    Dallas Lemon's Avatar
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    It ran fine for a long time (several years). I swapped in a cheap aluminum radiator off of eBay and that's when I noticed it. I can't say it was the cheap radiator, but that's when I noticed. Since then I bought a Napa radiator that did the same thing, then this big aluminum monster that I have now.

    Judging from the above statement, I would pay a little more attention to the radiator. You say the problem started when you installed an aluminum radiator. Then installed a NAPA radiator. Was it a copper core replacement? And now a really large aluminum radiator. Ever consider going back to a good heavy duty 3 or 4 core copper radiator? Copper exchanges heat better than aluminum. I'm sure the HP rating is sea level. Things change at higher elevations. Lower air density results in less heat being absorbed up by the air passing through radiator. You need more surface to reject the same amount of heat. Given the fact that it heats up at higher RPM also indicates it has a difficult time rejecting the excessive heat. Slow down and the coolant temperature drops.

    Another thought. You say it runs hot. Has it ever boiled over? Are you getting a false reading? Just a couple of things to think about.
    The Lemonator
    Jeepnut Extrordinaire

  17. #17
    Is that why almost all the vehicles now have aluminum core radiators?...
    The benefits from MILSPEC requirements are priceless!

  18. #18
    I am pretty convinced it is not the radiator. To be honest, I can't remember what prompted me to install the first aluminum (eBay special) radiator. The subsequent Napa replacement was a plastic tank/aluminum core type. The temp drop I see across the current radiator is around 30-35 degrees, which is in line with what I should be seeing.

    I have NO symptoms of a head problem, other than 2-3 cases of similar problems I found searching around online, so I'm not convinced that is the problem. I'm not convinced it isn't either.

    I am studying the idea of fuel mixture being the problem. I ordered a wideband air fuel ratio gauge. This will give me real time info to see if it is running lean when it is getting hot. If nothing else it will rule out this concern rather than taking guesses. If this is the problem, perhaps I can fix it with an adjustable MAP sensor.

    I do have a pacesetter long tube header that puts the O2 sensor much further down the exhaust stream than stock, at least double if not triple the distance from the head. I just can't wrap my head around how this would affect fuel metering.

  19. #19
    Dallas Lemon's Avatar
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    Quote Originally Posted by Knuckelhead View Post
    Is that why almost all the vehicles now have aluminum core radiators?...
    I guarantee the cost of the radiator plays more of a role in what is provided than the performance of the radiator.

  20. #20
    So I installed a wideband and at it is maintaining 14.6-14.8 under all but heavy throttle. At 60 mph in 3rd gear its turning around 2800 and not working hard at all but it gets up to 220 pretty quick. At 80 in 4th gear it's turning 2800 and working a little harder but will climb up to 230 pretty quick. It's holding 14.7ish the whole time until it downshifts to maintain speed on a hill.

    Is this too lean? I'm lost and ready to shit-can this engine and put a stock 4.0 in it.

  21. #21
    Ace's Avatar
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    I used to have a '55 chevy that would run hot at high rpms like your seeing. I tried everything I could think of and never did lick the problem.

    I was reading a similar story to yours on Pirate (I think), guys were giving all kinds of advice and he tried most, nothing seemed to help. The poster eventually installed a clear radiator hose and posted a video, the flow was terrible, like less than you'd fill a glass of water with. I think the pump was cavitating, I can't remember the exact problem but I remember thinking I wish I had a clear radiator hose on that old '55 to check the flow.

    Something to think about.

    https://www.youtube.com/watch?v=xGllevy08Rk

  22. #22
    I just spoke to Sean at SOS performance. He suggested I check the lift on the cam. I'm thinking I'll pull the valves cover (its leaking anyway) and put a dial indicator on to check. Damn near free troubleshooting...

  23. #23
    Sean nailed it. I checked the lift on the cam last night and it is no bueno. Shopping for a cam now.

  24. #24
    Flat cam? What was the cause you suspect? Not proper break-in? Break-in Oil? Poor quality cam?

  25. #25
    Quote Originally Posted by 74BuckinBronc View Post
    Flat cam? What was the cause you suspect? Not proper break-in? Break-in Oil? Poor quality cam?
    I'm suspicious of aftermarket cams, since I've gone through 2 of them in 105K on this jeep. This one has 55K on it and I think it wore over time. The overheating has crept up on me over the years.

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