2005 TJ/LJ Overheat story

Jeep Tech
1

Let me just say this LJ has a great habit of throwing me totally unrelated problems in rapid succession in an effort to simply never be ready to use when I want it…

Back story:

Replaced the E-fan controller to eliminate wires and fuses melting with a 70A system.
Drove to Ricky’s to get my new gas tank installed.

ran for 20 minutes at 220F then surged to 250 in about 5 seconds.
Pulled over, didn’t shut it off, temp returned to 220 in about 1 minutes at idle.
Limped into Rickys with a surging IAC (2600 rpm) and shut it down. Steve and Mark took a look. Determined it was in fact bloody hot, but no puking of fluids.
They did the IAC and gas tank and also an oil seal that I can’t remember at that time.

Ricky drove it around after service, no overheat at that time.
I picked it up from him. Drove to the Jamestown bridge. It pegged like before just before the toll gate. I shut it down, ran the e-fan and tried to start. No start until it was below 210. then I got it home at 220-230.

At this point, I adjusted my e-fan controller to be sure it would come on at virtually any temp. It’s set to start at 150F and always run. Thought maybe the controlls had it shutting off at a high temp or something stupid.

Drove it locally on 4th of July. Same issue, but happens in as little as 10 minutes if I am at cruising (above 40mph).

So far attack plan:

changed t-stat
changed water pump
flushed system twice
vacuum draw to get coolant back in (to avoid air lock)
pressure test cylinders to try and see if there was a head gasket issue. All service done. No real change

In the middle of all of this, I get a P0016 code. CPS is out of sync. Now I think Ricky did a seal on the distributor, but the sync is between the crank and the OPDA.
I look up OPDA issues… wall-paper worth of notes on the '05 OPDA failing, wearing the gears and going out of sync.

During all this, I buy a new muffler to change out my DYnomax V/T because it is recalled under warranty due to failing valves which cause it to flap and block exhaust flow (and make a racket).

Future plan A:

destroy this beat with C-4 and cry

Future plan B:

give up on the modified motor set-up and rob a bank so I can do a V8 swap and don’t Jeep for the next 5 years to save up for it.

Future plan C: (a.k.a. the rational one):

swap the OPDA with a modified crown Auto replacement with the bearing that allows oil flow
swap in the new muffle even though I don’t think it will fix the overheat
pressure wash the radiator and condenser in the grill to ensure air is flowing through and bugs/mud is not the killer here

test progress after each painful, time-consuming and expensive process.

If still no joy, consider replacing the radiator and/or e-fan under the assumption is has too much scale build to back flush out and/or the fan is losing CFM and can’t keep up to the highest demands.

I have not done a gas test where you can tell if exhaust gas is leaking into the coolant stream. I think that would conclude my finding to a head gasket or cracked head. I don’t want that to be the problem, but I am running out of ideas and a strategy to make progress on this fracking Jeep.

With all this story, does anyone have a novel idea on hi-speed overheat for a 05-06 TJ/LJ with an e-fan and aluminum radiator?

I was so happy Ricky solved my IAC issue and was hoping the racing of the IAC was somehow related to over heat. It’s not…

Any help on a strategy would be good. It’s with Jon Taggert locally here on the island for what was supposed to be a “failing waterpump is the root of all issues” diagnosis and fix. I need a plan now.

2

I have a exhaust gas in coolant test kit at the shop.

Also since your boosted might be a good idea to install an exhaust gas temp gauge to monitor your temps.

It might be a good idea to pull the radiator to clean out any mud, it’s really hard to get it all out when it’s behind an ac condenser
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3

Hey Ricky,

I just spoke to Jon While you posted and he confirmed he did the gas test… no gas in the coolant, that is a good sign considering I have an upgraded head and gasket, but does not really point to more against my plan.

Jon also showed me the radiator was clear. That is good for the low-hanging fruit about a radiator replacement, but it does not speak to the flow.

He suggested:

swap the muffler, OPDA change and then if it is hot, do a flow test of the radiator itself and then decide on a fan/ radiator change.

my first summer with this rig in a bad tune, it only ran hot when the e-fan burned up the fuse. If the fan was blowing, I was at 212 all day in warm weather…

4

1.) Possible obstruction in the cooling channels. Check local block/cylinder head/exhaust manifold temperatures with infrared thermometer.

2.) Can’t remember what is mounted on your bumper. Winch for sure. Lights? Remove them.

3.) Is there any chance engine is running lean? Check plugs.

4.) Was radiator and fan spec’d out for boosted engine?

5

I don’t think it is the muffler, It looked good when we replaced the cat

I would think about getting an exhaust gas temp pyrometer. I know my diesel jeep runs how when I pushing the EGTs into 1100-1200*f range

It is possible that the thermostat is bad. You could try running without one to test.

Before you were running super rich which would make the jeep run cooler. Also, It might be a good idea to go for a ride with a good scanner showing live data to check this.

This is what I’m leaning towards, you might need a radiator rated for a V8. You should also check the CFM your current fan pulls. The one I run on the diesel jeep is 3000CFM and it really helped

6

I’m a little late to the party, and most have already posted any suggestions I had before I got to the end of the thread.

Since there is a recall on the muffler and you are having an issue with it, get that replaced. Excess of back pressure can boost engine operating temperatures. I had a plugged cat in an old Jeep that I owned, and it caused it to overheat quite regularly until I figured the problem out. If this muffler is malfunctioning and creating additional back pressure to the exhaust, it could cause the jeep to run hot.

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7

I know the aluminum radiator and curved blade SPAL fan are rated for a flipping 454… I am concerned that the efficiency of the fan or of the radiator are diminished. Assuming the water pump is good and there is no “blood clot” in the block, I should have great flow through this radiator and somewhere around 2250 CFM on the fan. If this is a dual core rad and flow is blocked so it is only 70% or less flow, all these problems including the “high speed” a.k.a. high fuel burn overheat condition would probably happen. If I was made out of money I’d throw a mishimoto radiator with shrouded 2500 CFM e-fan in there and see if it helped, but that is a lot of ching to replace expensive components that worked fine 2 months ago and are not known to be the issue yet.

My A/f is right at 14-15 under most conditions and drops to about 12-13 under WOT (rich). I don’t think the mix alone is the issue. I read some stuff about finding an “industrial” radiator like the ones used on graters and diesel equipment that have no speed, but that also seems like a gimmick because if this radiator is scaled and plugged I should be able to throw almost anything in and see an improvement industrial or not!

I am going to ask Jon if he can flow test the system to determine if the radiator is plugged. I will probably power wash the soul out of it at that time and see what comes out although it looks clear with lights and scopes at the moment…

Thanks for all the feedback, it is helping me feel less like a “just replace everything” approach even though it may end up being more parts to throw.

8

I know the cat is good. and if anyone want to buy the $300 honeycomb valiant CAT hiflow that I replaced 3 weeks ago thinking that was my problem, Ricky has it at the shop waiting for me to do something withit. (Borla XR1 muffler too, all 3"in-out)

The VT muffler is fine at low pressure, but the valve is known to flap after a year (it’s been in there for about 2…) and they called them all back. If the high flow condition is causing the flap to act weird or to not open fully, I expect a similar, but reduced magnitude condition similar to the “plugged cat” argument. While I am not thinking that is the end of the story, I am replacing it with a Dynomax Superturbo that is static internally. It may not fix it, but it has to be done, so why not see if it moves me in the right direction right?

that is really all I can do on the exhaust side of things.

If nothing else, this should serve as a great “My TJ is overheating” checklist thread. All I am missing is a low speed condition on a fan engine where you all tell me the advantage of a 7 blade fan and tell me to check if the fan clutch is working and recommend a viscous brand replacement and then I say “thanks it was the clutch…” Not the end of this story…

9

Before spending money be sure to check LOCAL temperatures with IR thermometer. Checking downstream exhaust temperature after mixing will not identify local heating issue. All it takes is a little vapor anywhere in the system and its game over.

10

Also, did you replace the radiator cap?

11

Local temps with IR show that the needle guage at idle and the engine are not too far off (+/- 10 F or so)

The radiator did show a pretty big difference left to right something like 230- 180 in local pockets. Now a part of me says that is a good thing (heat is coming off) and another says that if the temp sensor I have installed into the upper rad hose (its a aluminum tube with a bung for the temp sensor for the e-fan) is reading 210 but portions of the radiator are at 180, I have dead spots in the radiator and it’s time to bend over on a new one…

if the upper hose sensor is at 220 and the lower is not collapsing and there is no air in the system, I would imagine all parts of the radiator would be similar to the gauge temp. A cool spot in the radiator is why I am thinking there is a reduced flow through all sections of the rad.

Never replaced the rad cap (it’s less than 4 years old) but I asked this morning to order an 18# cap to check that one off the list for a $10 investment. Since it never puked at temp peg, I am thinking it’s not the whole story. At 18#, the water won’t boil unless it is nearly 255F. Since it hit at least 240F and didn’t boil with the old cap, I’m not so sure that is the smoking gun.

Cheap insurance… I am still thinking it will be a rad replacement before I am back in business. I hope I’m wrong.

12

For shits & giggles, remove the supercharger drive belt and drive it. I wonder if it’ll overheat if it’s not boosting. Boost drives up the EGTs and high EGTs put a lot of stress on the cooling system.

It’s a quick and simple test that practically free

13

Tried that, no real change. it did take a bit longer to spike, but the ambient temp was lower too, so I don’t want to draw any false conclusions

I had a big revelation not stated yet is… Shroud.

I don’t have anything to block the core and direct the in-flow over the total area (corners not covered by the basket fan).

I wonder if warm air at higher speed is causing pressure effects that prevent the flow of cool air to act efficiently over the most area. Remember, I can’t get it to overheat at low speed.

I found an aluminum shroud with a 16" cut out that I will try out. It is another “won’t hurt you to do it” measure. I am not ready to say it’s going to fix things, but I actually have not driven this Jeep much in the hottest summer time ever once I think about it. The apparent “new” overheat may not present itself if the temp is below 75F.

Update:

I know for sure I have a SPAL fan rated at a real 2200 CFM. Confirmed with the supercharger folks it’s what they sell with the kit and has been working on the deployed sales. I still think the radiator efficiency is compromised. Might need a shroud and new radiator before i’m done.

Last time I drove it hard was up and back from Fall Crawl last year. Everything else was after it came back from VA around March and it was bitter cold. Only short trips and sub-75F since then until things went sideways. Again is that coincidence? Not sure, but the saga continues

14

The shroud not covering the whole radiator may account for the uneven temps you were getting on it.

15

I don’t know how yours is wired, but I would NOT recommend this sensor switch, summitracing.com/parts/DER-16759. Just installed two weeks ago for my e-fan and it’s already failed.

16

I liked my Hayden solid state, but the fan would draw big AMPs on start up and if it was going on and off all the time, it cooked the wire in that unit. I used a PAC-2750 from Dakota. at 70A, it can handle anything rated below 35A continuous which is basically anything… I am using a SPAL P/N ends 2049. 21A with about 1.0 static pressure, means under 45A on start… nice!

17

Update…

Hood vent…

No, I do not think hood vents “let hot air escape and cool the engine”. I also don’t think they “let air flow over the engine and cool it down”.

However, when I was doing race car stuff, one thing I did have to promote was creating an underbonnet to allow a low pressure zone behind the radiator at high speed. This basically meant having a pan below the radiator that prevented air from running under the bumper and going straight up the back of the radiator or circulating backwards through the fins and reducing flow from outside to inside. I don’t think I can make much of an under-bonnet in the lifted jeep, but I am thinking hood vents about 18" behind the radiator might help vent underhood pressure (and a bit of worm air) and help flow the radiator better. This may also support the “high speed overheat” condition I seem to have. Meaning the cooling capacity is adequate when I am not moving along fast, but high speed air does not seem to play well.

Anyone have ideas to support this?

18

All I know is that fluid dynamics can be completely counter intuitive. Its entirely possible that air flow is reversing through the radiator at higher speeds. A shroud would prevent reverse flow.

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I agree about the shroud benefit in that flow mode. I think it is pretty intuitive, but may not be ideal at all speeds. In reality, we are using speed as an assumed incoming air speed and pressure assumption. It may be that 70 MPH is a nice laminar flow with everything as it should be, but 40-60mph is some turbulent wash that stalls the fan and makes the pressure equal on each side of the radiator; killing the convective cooling we otherwise would get. That part is a bit hard to know by just looking at it.

It is very difficult to know what exactly is going on, but as you mention, if high speed is the issue and we shroud it to promote the pressure difference and force air through the radiator efficiently, I would expect an improvement.

The question is… do I need a shroud, underbonnet, vents or some combination? Without literally trying all combinations and having a suitable road test with constant air conditions, it will not be an experiment to rely on. My question is… Has anyone actually done one or many of these things and seen an engine temp improvement?

Forums searching on the interweb have proven inconclusive. For every one person that reports an improvement there are 2 that report none. Each time I find a decent discussion on the topic some fool argues that lower underhood temps fix overheating and it all goes sideways… Noone is looking at this as a speed-variable pressure effect, they all talk about fuel rails boiling and paint peeling and some random guy in Nevada says “I don’t have them and it’s 120 out here, so they are junk” and that is the end of the discussion.

Anyone here used e-fan shrouds or louvers with any real success with respect to engine temp before and after?

20

On my stock CJ engine, I would regularly overheat on hot days, or while crawling. At that time, I was not running a shroud, and was using a standard pulley fan.

After Jeep jamboree in Killington a bunch of years ago, and having a bunch of problems during that trip, I decided to make the switch to the dual electric fan set up, out of a Contour. At the same time, I installed vents in the hood.

I went from having a semi regular overheating issue to having a nice stable 190-210 operating temp.

When I switched to the Stroker engine, I kept the same set up, and still maintain the same temperature range regardless of my use.

Since I did both at the same time, I couldn’t definitively say what affect the louvers have on cooling, but I do believe it allows for better airflow through the radiator, exiting both under and over the engine without much resistance.

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