Jeepthing

Having issues with high coolant temps on the highway with my 5.3 swap into an 05' Jeep TJ. I have been searching, here and elsewhere, and while I have found a few people with the same issues, can't find anyone who has resolved their issues so hence this post. I apologize as this is long, trying to get all pertinent info down to start....

Have a 5.3L LM7 with 4L60E swapped into an 05' Wrangler. I have already tried a number of things to drop temps and have thus far been unsuccessful. Currently temps can get to 235+ before I hit the off ramp, this happens within 10 minutes of the on ramp. On one occasion right after the swap it did get HOT and puked coolant out the overflow (sustained 2,500 RPM for over 5 min going uphill). I do not have a surge tank, just overflow (hose from cap location to bottom of tank, hose off top as overflow under vehicle). I have been watching temps with the scan tool and not relying on the dash gauge.

Have a brand new Novak two core radiator that is fully shrouded with "trap" doors to supposedly help flow at higher speeds. Single SPAL fan that pulls TONS of air at low speeds, no issues at all below 60 mph and 2K RPM.

I have pulled the thermostat and checked it in a pot of boiling water, opens well at stock temp. In fact, opens much more than the second one I bought at O'Reillys, so the original went back in.

Cooling system was filled with a vacuum tool, so air in the system shouldn't be an issue. Filled through upper radiator hose into block, then vacuum tool to fill the radiator and the rest of the system. Have also tried to bleed the system out the front steam ports as well.

I removed the stock hood as no vents currently, dropped temps a bit but still see 223.

Removed the fan fuse and ran highway speeds only to see 235 once again. Stopped on the off ramp and reinstalled the fuse, temp immediately dropped quickly and by the time I went 100 yards at lower speeds was down to 200.

I currently have the small coolant hose hooked to the throttle body then to the steam ports. Considering bypassing throttle body and running steam ports to below the upper radiator inlet as I don't know if this is messing with flow. FYI both inlet and outlet on radiator is on passenger side, cap on driver side, steam hose on passenger side.

The ECM is getting the temp from the stock Jeep sensor installed in the front of the driver side head, apparently this is common. I am wondering about a possible temp difference between this location and the IN from the heater core at the thermostat.

I have checked with the dealer and a FSM for the Jeep that the heater core is a flow through design, no valve to restrict flow.

The problem is definitely 2K RPM and above under load, when held above 2K RPM in the driveway never gets above 215.

Running out of options, I think there is a coolant flow issue but not sure where to go next. Lots of people talk about removing the thermostat, running a restrictor, blocking the heater lines, etc....I just don't like those options as this engine works just fine in the truck, no reason it shouldn't in the Jeep.

Any and all ideas welcome. If you read the entire post thanks for that, I know its long...

Oscar Will

I'd start with thinking the coolant is not moving thru the system, either a huge air pocket (probably not) or something blocking flow. I wouldn't rule out a water pump at this point either. My 1935 Ford is close to the configuration you are running in the Jeep and I have run this thing thru Needles, CA in the summer at an ambient temp of 124 degrees outside air temp...the engine ran at 220 degrees with a single SPAL fan pulling air thru a Walker 2 row radiator. Initially I had a kinked lower hose that caused a similar problem to yours...gotta check that simple stuff.

I would definitely go to a closed system with a recovery tank and absolutely no air in the system with the correct 16 pound cap made for a closed system.

dantj

When you say you're using a stock jeep temp sender. Do you mean stock GM sender?

If its a jeep sender, it may be reading higher than the GM sender would read, giving you a false high coolant temp.

Jeepthing

Thanks for the replies, every idea is worth checking out...

Water pump is brand new as are all accessories. I am open to a high flow water pump but unsure of the benefits at high speed as they typically help most at low rpm...

The temp sensor is from the Jeep and is not GM. We checked with IR thermometer and it seems to be within a couple degrees of scan tool reading. I have a new one ordered just to try.

Intake air temp is higher than I would like also, will be making a "CAI" box soon as I have seen as high as 170. Higher on highway I think due to intake being almost on top of pass side header.

I am suspect of a few things adding up to higher temps...ie, high intake temp, poor air flow in engine compartment, possible air restriction through shroud. Not sure it's one major thing causing the problem but could be wrong...

Docked Wage

Do you have a winch and lights on the front of the Jeep?

These vehicles are as aerodynamic as a brick and those items wreak havoc on an already bad situation at freeway speeds.

Mine originally ran a little hot when I finished my swap at high speeds. I moved my lights and now it's not an issue. 95 Degrees and 90% humidity here in Florida and never gets hot with a single fan.

Jeepthing

Yes I have a winch and lightbar on the front. Removing the lightbar will be easy to check, the winch not so much as I can't remove it permanently.

Working on adding hood vents and relocating air intake currently, hopefully those two things help somewhat.

I am still suspect of coolant flow but not sure what can be done to change anything at this point. Possibly run without the thermostat to see if it is possible not opening fully at the correct temp thus restricting flow.

gagliano7

With the jeep still rev the motor to 2500 rpms and hold it there and make sure the hoses aren't collapsing. My friend had this happen on his 77 camaro. Do you have the steam vents hooked up correctly? It could be an air pocket.

Jeepthing

The upper hose has a spring and is not collapsing, the lower from our testing is not collapsing.

The vent lines are set up as stock I believe, but someone please correct me if I am wrong. There is a small hose that currently goes from under the Radiator inlet on the passenger side (opposite cap) to the stock throttle body connection. From the throttle body to the stock vent tube that spans between the two heads. As mentioned in the original post I would like to remove the throttle body connection as cold starts aren't really needed I don't think.

Thanks!

Pop N Wood

iTrader: (1)

You have definitely done your homework and covered all the usual suspects. I will bet it is an air flow through the engine compartment and not coolant flow issue. Otherwise you would see it at slow speed also. The fact you need the fan at highway speeds also tells me you aren't getting air into and out of the radiator. Most guys find the don't need a fan when moving.

Datsun put what they called a chin pan on the early 240z's. What they found is at highway speeds there was turbulence underneath the front of the car that prevented air from exiting out the back of the radiator. It was just a sheet metal pan that went between the frame rails for a about a foot or so behind the radiator. So look and see if there is some way to duct the air out the back of the radiator. Cutting some air vents in the wheel wells might help move air also. I've seen guys put fans in wheel wells in extreme applications. Another suggestion is blocking off any air paths around the radiator. Makes sure any air that comes in the grill goes through the radiator and not around it.

Docked Wage

If it's not overheating in the driveway or at low speeds it sounds like the same issue I had.

Post a pic of the front end as configured today.

Jeepthing

I have been thinking its coolant flow but now wondering if the air flow through the radiator is an issue. Currently the front end is configured as such...aftermarket trans cooler, A/C Condenser, Radiator. I think I may need to relocate the trans cooler...which is not going to be fun. Not a lot of room to work with.

Docked Wage

Here's what mine looks like today. You can see I moved the lights to the outside tabs of the tube bumper.

Once I did that my high speed cooling problems went away. Like I said 95 Degrees and 90% humidity for 6 months down here and this Jeep never gets hot.

Docked Wage

If you don't want to move the lights, you could try fabricating an air scoop under the bumper that funnels air up. Then you could create close off pieces under the hood that seal the air moving on the front side of the radiator and only allow it to go through.

I did this on a few of the vehicle programs I worked on when they could not pass validation.

Jeepthing

Temporarily or permanently removing the light isn't a huge issue, however moving the trans cooler is a much larger project...

Thanks again to all who have provided suggestions, I need to find some time to get these changes made.

8yourz28

I have an LQ4-4L60e TJ. I went with an LS swap radiator from Superior radiator, and a Ford Taurus electric fan. I have never had any issues with cooling. the fan rarely kicks on. I also run a winch and 2 large KC lites on the grille gaurd. I would be very suprised if you are suffering from an airflow problem.

Jeepthing

Thanks for the post, any more details on your set-up? Do you have the stock condenser and a trans cooler in front of the radiator also? How is your steam vent port configured?

Punisher8738

iTrader: (1)

I'll definitely have to follow this thread. I've got a heads/cam forged lq9 in my LJ. On the highway I'm experiencing the same issue. I called Novak and was told I have the older shroud design without the vents. Bad part is its going to take a few weeks to have it shipped. I was also told I have their single core radiator which according to Novak rep cools better than the double....

While waiting on the shroud which I may not use, I'm upgrading to a new Lincoln Mark VIII fan I found on ebay. I honestly believe the Novak shrouds are too shallow of a design and cause the air flow problem.

Like you I've driven without the bumper which would only leave the large trans cooler and ac condenser as an obstruction. Before I swapped in the LQ9 I ran a Ripp supercharger which had a large heat exchanger roughly the same size as the transmission cooler so I'm sceptical of it being a problem.

Jeepthing

Interesting, Novak told me the two core radiator cools better than the single core, they mentioned a 10-15 degree difference. I was skeptical of the almost pinhole size passages in the single core restricting coolant flow. I started with the single core with the non vented shroud and they recommended the two core with vented shroud...no change. I also added vents to the original shroud and no change. While driving with the hood off the driver upper vent doesn't "open" much at all with the new shroud....

What is the reasoning behind the fan change? Increased CFM? I know I don't have space for a deeper shroud...

It is possible low speed cooling could be adequate with no shroud, may have to try that after the hood vents. I will also be adding a seal between the grill and hood as found stock on the JK wrangler, I think some air may not be getting directed through the radiator.

I know adding a trans cooler in front is not uncommon, I really hope that isn't the issue as it is probably the hardest thing to change at this point.

Can anyone confirm yes or no in regards to stock trucks disabling the fan based on speed signal from the VSS? I have read conflicting info on this.

Lets keep this going, there are obviously several of us with this issue....

Punisher8738

iTrader: (1)

I'm upgrading the fan for more cfm and the shroud itself is deeper to allow more airflow at speed as well. Non scientific test but I compared the two (spal 16"/mkviii) and there's no comparison. It pushes a lot more air. My jeep never runs above 210 around town no matter what the temp is, so I know it's only an at speed issue. I spoke with a rep at Evans cooling because I was considering their high flow pump. I have the same symptoms as you and I was told it was more than likely air flow. He suggested I try adding a bypass valve to the heater core feed which I did and noticed a small drop but I still warmed up on the freeway down from 235 to around 225 on 100 deg weather at speed of 65/70 (2500rpm) He also suggested looking into air damming affect which could be caused by anything from the winch to the fan shroud depth. Since I don't have the vented shroud, I decided to try the lincoln. Every thread I've read about people switching to he lincoln has been a success. I'll more than likely have to swap to a car water pump to fit the fan. if that doesn't work i may have reached the cooling capacity of the radiator and will have to look into a custom one. I'll let you know the results when it's done, I'm in the shop now dealing with a bad autometer gauge and requiring the harness using leash electronics waterproof relay boards.

Interesting thought on the seal, any pics? I've also considered making an air dam as suggested by Evans rep. He said an air dam will create low pressure behind the radiator redirecting the air to he pulled thru. Just a thought, I've got some old plastic I may use to create one if the fan alone doesn't fix the issue.

Jeepthing

Thanks for the info. I also have absolutely no issues at lower speeds, could be 100+ degrees out, and the system works great. Out four wheeling the temps are well within check, its just getting there and back that is the issue...

I installed the hood vents and relocated the air intake today. Wont have a chance to test until tomorrow probably. I will report back with any changes.

You mention the heater core bypass valve, sounds like a worthwhile change as a 10 degree drop is huge in my opinion. A change like this with some airflow improvements and we could be in business.

You mention adding an "air dam", not sure I can picture what you mean. I have no problem removing the shroud and trying that too, may have to here soon.