Fun with heat....

[robert j. yates]

Thanx...this discussion is helpful in that it causes me to go back and think about how things were figured out.

I'll start with the IR gun....I am aware of the issue with aluminum and have always used blue painters tape so as to cause a more consistent reading as compared to as you say, the rubber hose. Is it exact? I have no clue but I do get consistent readings each time the issue is investigated so I am ok with my process.

As for restricting flow....that was a thought early on and as a result, the outlet hose feeding back into the radiator was pinched off and the Jeep was run several times on a freeway section known to run the temp guage up. No difference was recorded.

I know it sounds like I have all the answers but the problem of warm water temps has been a persistent issue for many years so I have been around the block a few times.

I really do think my AC condensor is the biggest culprit but I do not want to junk my AC...I wheel to much in a desert climate for the to be a paletable choice.

 

[robert j. yates]

...some progress updates

What this set of pictures show is that I will be using dead space inside the passenger side rear corner to locate the engine oil cooler. It is only roughed in at the moment but we are pretty sure this will work out just fine. You can see the hardline run on top of the framerail and each end will be connected via braided hose and a/n fittings.

FYI....the cooler face will have a piece of 12ga off-set in front of it (inside the wheelwell) so as to protect it from debris kicked up by the tires. The last picture was taken looking up inside the corner.

I also have the Genrite enduro tank in place. I lost an inch of clearance as compared to the ACF skid and stock tank which the Genrite replaced. I'm ok with that as I have an extra 5 gallons of fuel capacity now.

 

[robert j. yates]

...one more showing exactly where the cooler will sit.

 

[1leg]

Did you by chance sonic check your cylinder wall thickness when you rebuilt the motor?
Reason I ask is because, I had a Pontiac 455 block that would over heat every time I stopped in freeway traffic or stopped on a off ramp. A buddy suggest I try another block. I did and the problem went away. I only changed the block except for a few gasket I reused every part I even reused the head gaskets. I had the Bad block check afterwards and it had a couple of cylinder walls that were to thin.

Just an idea.

 

[robert j. yates]

Thanx...the issue has been consistent over 2 different motors so I don't think thats the problem. We've also investigated on whether there is water in the oil and thats a negative. Its also a stock block with 12,000 miles on it so I don't think thin walls are the issue either.

 

[elcoyote]

I am curious: Has anyone here ever overheated a 4.0 enough to damage or blow it? I run an Autometer temp gauge and it regularly shows temp at 220. Sometimes on steep grades it gets up to the 240-250 range. My engine has a supercharger on it and I expect higher than normal operating temps. My engine was rebuilt at 220K and now has 350+ on it. I am starting to wonder if it is the gauge that cause my worry rather than the actual conditions. One of the stupid things I have noted about the temp sensor for the radiator coolant is that it is placed in the absolute hottest place in the engine compartment: at the top rear of the engine near the firewall on the exhaust manifold side. I have a sneaking suspicion that if it were moved to the front of the engine it would read differently.

 

[ntsqd]

The late, widely acknowledged expert on ACVW's, Gene Berg, wrote that any temp gauge that cost under $250 was suspect for both it's repeatability and it's accuracy to within limits acceptable for engine use. The first time I read that was in the late 80's. A $250 gauge then would be, what, a ~$400 gauge now?

I've never found anything that would solidly support a contrary opinion, though I do think he may have been a little over zealous in his statement.

The rear of the head would give you the hottest coolant reading, and this is a good thing. The rear-most cylinder is the most likely to have heat related detonation issues.
Perhaps more modern American power plants have better coolant flow layouts, but most of those I've encountered have really crude designs. Coolant flow paths haven't changed much in 80 years, though I'm guessing that emissions will force some improvement in this area. The best I've ever seen, short of a modern engine, are the International Harvester gas V8's, and even they lack a bit on the cool coolant distribution.

Pull some coolant, in a heater hose sized conductor or bigger, from the rear of the cylinder head up to the uphill side of the t-stat (so that you're not by-passing it), and watch what that does for your operating temps. On my old 302 Ford it was worth 10-20 degrees depending on conditions.

 

[robert j. yates]

I've had a good mechanical guage plumbed in underhood for testing purposes and frankly, between that, the IR gun and what the ECU is telling me on my Scanguage.....the 220-235 temps that I see are pretty much accurate.

That being said...I'm not trying so much to knock them down to 210 which I doubt is going to happen anyways, but rather to build in reserve so that when my rig does see 235 I don't have to worry about it.

 

[BigAl]

I don't know what you are using, but I switched to a flexalite reverse rotation mechanical fan and ditched the clutch. I dropped ~10 degrees. The fan and adapter were ~$40. I tested it by holding a sheet of paper in front of the radiator, the flexalite seemed to pull a lot more air.

 

[robert j. yates]

We finally got everything back together and tested the oil cooler. I have no pressure spikes with 19lbs at idle and 45lbs at 3000rpm.....exactly as before. I also get an 18* drop in oil temperatures with the fan enabled which is exactly what I was after.

We have a couple of leaks to button up and then its on to road testing it. I will have to get some foil insulation up in the rear corner above the cooler so as to protect the electrical for the tail lights and trailer. The cooler gets pretty warm which is a good thing. Better that than my oil. Final pix to come soon.....

 

[ntsqd]

Follow-up report?

 

[robert j. yates]

Follow-up report?

Here ya go:

http://www.stu-offroad.com/engine/cooling/cooling-1.htm

 

[4Rescue]

The physical size of the radiator is limited by the Jeep but I do have a 2 row all aluminum Novak radiator in place with the stock shroud. My hood is vented, I run a Hesco hi flow t-stat housing and water pump, 7 blade fan conversion and heavy duty fan clutch. The Jeep runs warm and this has been thoroughly tested and verified with mechanical guages and the temp gun.

The tranny is on its own 2 cooler circuit and is not even tied into the radiator although the engine oil cooler I am currently using is. The tranny was never an issue until I started pulling the Horizon.

I've been chasing this problem for years..basically since the Jeep was new. Its never overheated, come close to overheating or swept the guages which is something TJ's will do if the computer thinks things are to hot. All of that being said, I am after durability and margin of safety....I spend alot of time wheeling in the desert and I don't need things getting hot. All of that being said, allelectrical componants are tied into relays...its not a huge deal.

:smileeek: All of that and you're still having overheating issues... Maybe if you go back to stock it'll go back to not overheating??? Seriously, I have no idea, but it sounds like something else is horibly wrong if, after all of that cooling capacity has been added, you're not seeing lower temps eh...

Cheers

Dave

 

[robert j. yates]

It has never overheated but it runs hot and if you read the report, it did it while it was stock as well. I know of a 97 and 2 other 98's that have the same issue I do so I am past the point of trying to understand it and pretty much done with dealing with it. I can live with 220 and ac which the current rond of mods has accomplished. I cannot live with 230 and no ac.