Keeping a 4.7 cool

Performance mods and Advanced Stroker discussion.
Spjewell
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Re: Keeping a 4.7 cool

Post by Spjewell »

I may see my issue here, this may be a noob mistake, but I did not realize there was supposed to be a spring in the lower radiator hose. Therefore I am 99% sure it is not there (if it came with the O'Reilly hose I purchased than it is in there). The entire engine and cooling system is new so assume I can rule out most of the other items listed.

To second this potential problem, I was running good around town low rpm=low pressure in the lower hose. While offloading up and down hills I was running higher rpms, resulting in potentially higher pressures. Any advice on where to get this spring? If not I will hit the old faithful's (google, ebay, amazon)
Cheromaniac wrote:
jsawduste wrote:Be it running at 80 mph or crawling at Rocks and Valleys. Do yourself a favor and revert back.
At 80mph there should be enough airflow through the radiator to keep the engine cool without a fan.
If the engine's running hot on the highway, the problem isn't the fan(s) but either insufficient airflow through the radiator (blocked fins, obstruction in front of radiator) or insufficient coolant flow through the radiator (clogged up radiator or cooling passages, insufficient core area, worn water pump vanes, thermostat stuck partially closed, lower radiator hose collapsing due to rusted out internal spring).
An engine that runs cool on the highway but runs hot at rockcrawling speeds has insufficient fan capacity to pull cool air through the radiator. Some aftermarket fans don't cut the mustard and others that do may have a high amp draw, requiring an upgraded alternator to prevent the battery from being drained. Large mechanical fans don't have that problem but have other disadvantages such as parasitic HP drainage and shortened water pump life (if mounted on water pump pulley) so pick your poison.
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Cheromaniac
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Re: Keeping a 4.7 cool

Post by Cheromaniac »

Spjewell wrote:To second this potential problem, I was running good around town low rpm=low pressure in the lower hose. While offloading up and down hills I was running higher rpms, resulting in potentially higher pressures. Any advice on where to get this spring?
It's the opposite. The water pump spins faster at higher rpm and generates more SUCTION on the lower radiator hose. If the spring is missing/broken, the hose collapses and the pump draws less coolant through.
Unfortunately you can't get a spring on its own. You'd have to get another lower radiator hose with spring.
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SkylinesSuck
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Re: Keeping a 4.7 cool

Post by SkylinesSuck »

Just curious if you ever got this issue resolved.
BADASYJ
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Re: Keeping a 4.7 cool

Post by BADASYJ »

The fans are what is killing you. Either go back to a mechanical or get one big name brand electric fan WITH A SHROUD.
On a stock system, the 160 t-stat will never close which in turn dosent let the coolant stay in the heat exchanger (radiator) long enough to properly transfer the heat to the outside air. Basically same as running no t-stat. We have very small heat exchangers in our YJs which means less tolerance to overheat, so we have to slow the flow and give time for the coolant to transfer the heat. We do that by running a 180 or 195 t-stats which will hold the coolant a little longer so it can properly transfer the heat. Now being you have a four row exchanger I would think that would off set the 160 somewhat as you now have more cooling area allowing a better transfer of heat. Still I would pull it out and run a stock temp stat.
Honestly though, I cannot for the life of me see how the larger heat exchanger will cause you to overheat. That runs contrary to everything I've ever learned while in the Mechanical trade. So long as there is adequate air flow the larger the heat exchanger is the more heat is exchanged, regardless of what it's in as heat dosent give a shit what it's heating.
jsawduste
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Re: Keeping a 4.7 cool

Post by jsawduste »

BADASYJ wrote:The fans are what is killing you. Either go back to a mechanical or get one big name brand electric fan WITH A SHROUD.
On a stock system, the 160 t-stat will never close which in turn dosent let the coolant stay in the heat exchanger (radiator) long enough to properly transfer the heat to the outside air. While you correct in the 160 opening sooner, once its open the coolant will flow just the same (rate) as a higher rated thermostat. Basically same as running no t-stat. We have very small heat exchangers in our YJs which means less tolerance to overheat, Ahh no. by comparison the Heat Exchangers as you call them are actually on a higher efficiency side then most other applications.so we have to slow the flow and give time for the coolant to transfer the heat. We do that by running a 180 or 195 t-stats which will hold the coolant a little longer so it can properly transfer the heat. Go back to the other response. The higher temperature the engine runs the more efficient it is. The whole ECM calibration and cooling design is based on a nominal operating temperature achieved by the use of a 195 `stat. Now being you have a four row exchanger I would think that would off set the 160 somewhat as you now have more cooling area allowing a better transfer of heat. Still I would pull it out and run a stock temp stat.
Honestly though, I cannot for the life of me see how the larger heat exchanger will cause you to overheat. That runs contrary to everything I've ever learned while in the Mechanical trade. So long as there is adequate air flow the larger the heat exchanger is the more heat is exchanged, regardless of what it's in as heat dosent give a shit what it's heating.
Larger is not always more efficient. There are too many variables to make a blanket statement. Folks are often confused by heat conducting ability vs. heat dissipating capability. Two very different factors.
Not trying to be a butthead but where do you come up with this stuff ?
BADASYJ
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Re: Keeping a 4.7 cool

Post by BADASYJ »

Yeah bro, you are being a total doushe bag with that last comment you made. Your condensending attitude really rubs people the wrong way dude. You are nit picking everything I post, yet you do very little in terms of providing or correcting me with any valuable knowledge.
jsawduste
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Re: Keeping a 4.7 cool

Post by jsawduste »

Sorry you feel that way BA. Just pointing out the falsehoods in your logic and thinking. Nothing personal intended but damn son......

Enough information has been provided to do your own research and thought processes on.
Spjewell
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Re: Keeping a 4.7 cool

Post by Spjewell »

SkylinesSuck wrote:Just curious if you ever got this issue resolved.
Issue has not been resolved yet... still taking in info and thinking on the solution. I am out of town on business so I haven't had time for the jeep. Did look into the spring issue, and 1. definitely no spring in there, 2. seems to have enough pressure at idle that it isn't collapsing. Possibly it collapses at higher RPM, but the issue still stands... I get it to about 220 ish put it in the shade in the garage and it can only stabilize its self (stays right at 220).

Next course of action will be to flush the system and run it with water & new T-Stat. just in case its a bad mix of antifreeze/water or a stuck/clogged t-stat. If that doesn't work, I will put in a stock single row radiator and a Taurus fan/shroud (have one sitting in the garage). Although I own a jeep I don't like wasting money ;-)

I believe the issue is 100% with the fans... the issue being back pressure due to the increased thickness of the radiator. Fans in general don't do good with back pressure, so I think when I run them up I am only pushing/pulling a small volume of air through the radiator, the remainder of the air is going around the fans.
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Re: Keeping a 4.7 cool

Post by SkylinesSuck »

FWIW I recently replaced my 2 core brass radiator and 15" flex a lite (with integrated shroud) with a 4 core aluminum unit that is much thicker and a 16" flea bay fan (no shroud). The brass rad was allowing the Jeep to get into the upper 220's on very hot days with the a/c blasting while climbing long hills going about 45mph. It would also slowly creep up into the 220's idling with the a/c on. Now it stays rock solid at 205-210 driving down the road under the same conditions. At idle though, it was getting too hot with the crap fan and no shroud. I have since purchased a shroud and a Spal 16" medium profile fan, and it cools awesome under all conditions. I let it sit idling in the driveway in the direct sun on a 95* day with the a/c blasting for an hour and it never went over 208*. Very happy with the set up.
Spjewell
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Re: Keeping a 4.7 cool

Post by Spjewell »

Finally back from my work trip in Memphis, time to get down to business. I have been doing lots of research, and have a number of potential fixes. But I think the best way to tackle this is to assume nothing is right and check it all. First item on my list is timing, can anyone tell me what this should read? Currently I am at 12*, and can't find any info as to if this is good or bad. I feel this is high and I might be off a tooth on the dist? But then again Jeeps don't run on feelings :-)
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Re: Keeping a 4.7 cool

Post by Cheromaniac »

Spjewell wrote:First item on my list is timing, can anyone tell me what this should read? Currently I am at 12*, and can't find any info as to if this is good or bad. I feel this is high and I might be off a tooth on the dist? But then again Jeeps don't run on feelings :-)
The ignition timing at 12* is spot on and is non-adjustable 'cause it's programmed into the ECU. You can manipulate it by slotting the holes in the crank position sensor and moving it. Rotating the distributor has no effect on ignition timing whatsoever. Instead it alters the timing that the injectors fire and how it's related to the spark using the signal from the cam position sensor.
Read my previous post about the spring in the lower radiator hose.
Spjewell
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Re: Keeping a 4.7 cool

Post by Spjewell »

I did look into the radiator hose spring, and it is not there however I determined it is not the primary cause. I warmed the car up, then watched the lower hose for any signs it was collapsing, it showed none and the temp continued to raise.

I will put one in next time I drain the coolant.
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Re: Keeping a 4.7 cool

Post by Cheromaniac »

If you have an IR temp. gun, point it at the upper radiator hose and the lower radiator hose with the engine at a hot idle and take some readings. If the temp. gradient between the two is small, this would indicate that the radiator isn't working efficiently.
You didn't answer my earlier question about whether your engine runs hot only at slow speeds, only on the highway, or all of the time. This will narrow down the list of possible diagnoses.
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Spjewell
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Re: Keeping a 4.7 cool

Post by Spjewell »

I will pick up a ir-gun this week and see what's going on. Seems to be hot at all times (highway, around town, and idle)
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Re: Keeping a 4.7 cool

Post by Cheromaniac »

Hot at all times usually = bad radiator
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