Hello all,

I need a set of fresh eyes on this challenge please.

Here's the background- 98 Disco 1 with 193,500 miles. The problem surfaced when my wife and I were pulling up the backside of Jacob Lake on the North Rim of the Grand Canyon in July 2013. We had our Adventure Trailer behind us, 100°F and going slowly up a steep single track. The trailer weighs about 1,000 lbs.
We didn't have the UG yet, but the factory temp gauge started climbing, so I pulled over right at the top and stopped. The electric fans were running and I shut the engine off after a few minutes of idling. I heard gurgling noises from the gas tank, and it took an hour of cooling off to restart and limp it into the campground. It would run for about 2 - 3 minutes and then die. I could restart after about 5 minutes of sitting. The temp gauge read normal during the limp-in.

After having a buddy pick us up with our diesel truck and flatbed trailer, I replaced the tstat with a 180°F failsafe unit. I did the water test and had to get a second one as the first wasn't opening until over 195°F. I also bought the UG!

I replaced the fuel pump for the gurgling noise, as it had a hot die-out issue when ambient temps were over 95°F - common here in north-central AZ in the summer. No more fueling or die-out issues.

This past summer I replaced the Flex a Lite electric fans that had started to fail with Spal fans and a Dakota Digital programmable fan controller. I can control the fans independently to come on at different temps - the low comes on at 190F and the high at 195F with the temp read from the factory temp sender. I cleaned the temp gauge connector as it had crud in it. This set up pulls some serious air - it will blow up dust clouds behind the Disco on a dirt road when sitting still! I also had the radiator disassembled, cleaned out and rebuilt. The rad shop said there wasn't any junk built up in the radiator. I replaced the 180°F fail-safe tstat with a normal one after it failed open in Flagstaff during the summer - same temp. My water is water and my oil is oil, no foam or crud anywhere. I double checked to make sure the spring side is installed inside the intake.

I normally run up to 192F when starting out on the road, then the tstat opens and it drops back down to 176 - 183 on the road, depending on speed and hills. In town it will run 183 - 188 regularly.

So here's the problem - after all this, the engine will still run hot (>210F) on a slow, loaded uphill pull. We went to Kingman with the trailer in Oct 2014 and went up to Hualapai Peak campground - a long, steep, steady pull of 6 - 7 miles. Thankfully, the UG saved us bad news there, as we pulled off the road several times to let the fans cool the rad down to 193F or so before we started again. We had more of the same going home on a rolling dirt road with a tail wind, so there was little to no airflow across the radiator. We had to stop several times to let it cool off. Once we could do 30+, everything was fine.

Once we got home, everything was normal, no heating up, nothing over 192F when sitting with the fans on. During all of this, I've been chasing a P0430 code intermittently, but saw that the right side upstream o2 sensor was lazy and replaced both upstream sensors. The engine runs better and the code hasn't shown back up in a month of driving.

I thought the water pump was worn, as it was the only thing not replaced. I just pulled it out with 105k miles on it and here's what it looks like:
Not what I was expecting! I thought the impeller would be worn to nubbins, but it's not.

Looking back, I realize that I didn't water-bath the new 180F tstat. At this point, that's the only straw I have left to grasp. I'll check the opening temp and report back.

Sorry for the novel, but I wanted to get detailed info out there to work from. I'd love to hear thoughts and opinions on this - I'm at a standstill. It runs fine on the highway and anytime I'm over 25 - 30 mph with the trailer, but it wants to run hot below 15 mph even with the fans.

 

Well, there goes that straw...

Just checked the tstat, it starts opening at 180 - 182F and is fully open by 188F. I checked it several times with a couple of different thermometers and they all agree.

Puzzling.

 

You never mention your mechanical fan or the clutch that drives it. Are you still running it or did you swap it out for electric fans? Your post is sort of confusing regarding that.

 

MM3846, I'm running dual Spal electric fans with a Dakota Digital programmable fan controller. These replaced the Flex a Lite electric cooling fans I had on for 7 years and had started to fail.

The first fan is set to come on a 190F and the second one at 195F, read from the factory temp sender.

 

I noticed that under load you run hot...have you made absolutely sure to thoroughly burp the cooling system?
You don't mention a history of head gasket replacement in your post. I assume w 193k they have been done at least once...might be time to do again. Running hot under load (once other factors have been eliminated) is a sure sign of head gasket issues. Regardless of oil and coolant mix signs.

 

Shiftonthefly1, I burped the system after installing the radiator and tstat with the method I read on here - roll the rt frt tire up on a ramp after warming up and let it run to purge the air. I did this a few times over the first week and haven't heard any gurgling noise when running.

It will pull hills just fine without the trailer, it is just when the ambient temps are high and speed is low with little airflow pulling the trailer up offroad hills that it starts getting hot. Unfortunately, that's exactly when I need it to run cool!

Thanks for the head gasket suggestion, I will test the coolant for exhaust gas contamination and report back.

 

Yea engine working it's hardest. I am familiar with the high Temps we can get here in the southwest. There is a thread here about a guy converting to a GM style radiator. I'm not sure it really cools better or his old radiator was shot. Seems like the stock cooling system works if all the parts are up to par. If you got airflow...a clean good radiator..good coolant with no air bubbles....good coolant flow...you should be fine. Something seems off.

 

There comes a point when you are just working the truck too hard. I'm not a fan of replacement mechanical fans with electric... whats the CFM of the ones you are using? The stock probably is ~4000CFM.

 

Thanks for the input folks! I fully realize that this isn't a normal thread question with a problem that has been seen a thousand times, so I appreciate the honest and thoughtful feedback.

Just to clarify in the discussion - this is not a new system or set-up. We've had the trailer for 9+ years now and have dragged it all over AZ, UT and CO. We've actually lightened the load in the trailer, taking out what we don't use very often.

Likewise, the electric fans have been in for 8 years now. First was a set of Flex-a-Lite that lasted 7 years and didn't have nearly the CFM flow of the Spal electrics in there now, nor the temp control that I have with the Dakota Digital fan controller. The Flex-a-Lites CFM is listed with no restriction, while the Spal fans are. Spal is an OEM manufacturer for most major carmakers around the world, and their designed lifespan is 10,000 hours. I spent a bit of time talking with the engineer at Spal USA about my application and what I needed.

MM3846, I agree with your statement on the OEM fan/clutch setup, but switched over when we started running hot in Death Valley during a spring run. I've never been able to find the specification of the OEM fan CFM draw listed anywhere. I've found lots of theory, but no factory figures. The Spal fans are listed at 1630 CFM w/ no static pressure and 1450 CFM w/ 0.2 inches Hg, which is what a new, clean radiator is rated at. I have 2 fans, so am reasonably running 2900 CFM. From experience, I know on my rig that the OEM fan/clutch when hot would not pull nearly as much air as the current Spal fan setup. I can stand behind the Disco with the fans on and feel the airflow and see dust being kicked up, whereas that never happened with the mechanical fan and clutch, even with a new clutch.

The overheating doesn't happen every single time I hook the trailer up and head off road. The day that it overheated last, we came up out of the Hualapai canyon with no issues at all. This is the only road you can drive down to the Colorado river and is one rough mother. The UG temps read 192 - 194F at the peak - fans came on as programmed and everything cooled down. The road was not a straight up, non-ending climb and it was 10 - 15F cooler than later that day when we did run hot, but the daytime high was only 80F, nothing really hot at all. This was last October.

What I'm wondering now is if the P0430 code that has been on-again, off-again has anything to do with the overheating. I recently replaced both upstream o2 sensors, with the RT (passenger) side being black and more cruddy than the Lt side. The engine has more power now and is getting better fuel economy - could this imbalance in fueling have been part of the problem?

I'm going to put everything back together, run it and do a coolant test to see if there is exhaust contamination. If nothing shows up, I'll pull an oil sample to see if there is coolant detected in the test. That will confirm a head gasket issue if there is one.

If you've got thoughts, please share them and I'll report back when I have test results of if I see anything else!

 

I forgot to mention that I'm still running stock gearing. I'm planning on swapping to 4.10s as I'm running 235/85R16 tires with a 3" lift. I know this will work the engine harder and keep it out of it's deeper power band, but it might be contributing to the heating issues on really steep roads.

Anyone find they ran cooler offroad after re-gearing to a lower ratio?