Hey guys,

So...I recently had to replace most of my cooling system due to a catastrophic failure of my fan caused by broken motor mounts on my '99 D2 (122k miles, HG done at 96k, all other fluids and service are up to date). I replaced the (new) radiator, fan, motor mounts, water pump (working, but had a little wobble to the shaft), upper shroud, and the lower airbox. (Note: I did the PAS pump too while I was in there, but that was completely unrelated.)

While the truck is moving, I'm seeing pretty steady engine temps between 189* and 199.6* on my Ultragauge, but when sitting still for any extended period of time, I'm seeing the temps climb to 210*+. The temps while sitting still do stabilize if I turn the heater on full blast.

The truck hasn't been allowed to get above 212*, and doesn't appear to be pressurizing the cooling system or consuming any coolant. Last Friday after I completed all my work on the truck I took it for a spin and it through a P1884 code after it was started up. After looking it up, I decided to clear it to see if it came back, which it did on our way out to an off road event the next day.

Saturday morning, we loaded up our D1 and the D2 for a day of fun, and headed out wheeling to an ORV park in NE Ohio, and was able to control the temps with the heater while out on the trails, driving a total of ~200 miles. Highway temps were ~194* with the AC on and 80*+ outside. Trail temps before the mud stayed ~194* with the heat on. Keep in minf that all of this was before what I'm about to tell/show you below.

In the interest of full disclosure, I did have an encounter with some mud on Saturday...I'll be rinsing my radiator out with a garden hose this afternoon due to the below incident while wheeling, but my temperatures weren't satisfactory prior to this, so my belief is that something wasn't right even before the water (mud) hazard pictured below...


...this took out my MAF, which caused all kinds of grief for a while. Luckily I carry a spare. Switching to the new MAF did seem to stabilize the temps a little, but I'm not sure whether the two could be related. It and a clean, dry air filter definitely resolved all of error codes.

So here is my first question. For those of you using after market temp gauges, how much fluctuation are you seeing in your temps? Prior to the fan wrecking my radiator, and other parts, I was consistently running between ~189* and ~197* with only occasional spikes to 204* during especially tough climbs in hot weather.

Like I said, I'll be flushing any silt out of the radiator fins shortly, but as things weren't exactly back to normal (great) before this, I'm curious what kinds of temps the rest of you are seeing, and whether you have any other suggestions.

Beyond mud in the radiator fins, does this sound like an air bubble, or do you think I've ended up with lousy radiator? Any other ideas? Could changing the MAF cause any changes in the operating temp?

 

Overall they sound pretty normal to me. Are you running a soft spring thermo? If so, those would definitely be high. I am running a normal OEM thermo and I range from about 194 highway +/- a few to about 200 around town plus or minus a few. Sometimes my temp will spike to 212, but it comes down. And I mostly only see 212 when it is cold outside like 70 degrees or lower. When it is hot out it usually doesn't spike that high. I use an Ultragauge to measure temps.

 

I'm running a stock thermostat, not the 180* variant. It was new as of 96k miles.

 

195-200 moving is fine, 210-215 idling is fine. If it goes above 215 and never drops, then there is an issue with the fans, sitting idle it should go from about 210-215, back to 210ish or lower when the fans kick in, then back up to 215ish untill they kick on again.

 

Well, I guess I'll have to bite the bullet and see how high it goes. I just used the garden hose to blow the silt out of it, and off a fair bit of the rest of the engine. I had to drive it at lunch time and it got to about 212* in stop and go traffic, but it was still going up, so I don't know if it would have stabilized at some point. Hopefully this was part of the problem.

What disturbs me the most is that while the temps fluctuate depending upon the speed I'm traveling (faster = greater airflow and results in drops in temp, which makes sense), but as far as I can tell they always seem to be trending upwards...

 

The mud caked up will definatly insulate the radiator more and cause it to become heatsoaked faster, and impeded cooling... but still sounds ok to me. Are all the fan blades in tact? Alot of bent fins on the radiator (they sell a plastic comb to fix those too)?

On a hot day I might see a spike of 220ish, but it usually comes down pretty quick with the fans on or when I start moving. You should be good above that short term as a test to see how high it gets and if and when it levels out on its own, but above that I would definatly pull over and look for problems.

 

Fans are all looking good and the AC fan is definitely working. I did bang some of the radiator fins up on the new radiator when I installed it, (but I didn't think it was that many) so I'll definitely pick up a comb and straighten them up.

FWIW, the pile of silt that I washed out of my winch tray was pretty impressive. What came out of the AC and radiator was less exciting, but still significant.

 

I have the soft spring as my temps ran high, and a completely new cooling system too due to a faulty fan. I run in the same range regardless of outside temps. I run in the high 190 range on the highway, 200-204 on the back roads, 205 in stop and go traffic, and up to 210-212 if sitting still for a long time. I sat in NYC traffic on a 100 degree day and cruised on a 50 degree night with the same temps. I'm sure come winter it will run a tad cooler at times, but not much.

 

I run the 180 Tstat with ultra gauge. I maintain 194 most of the time and long idle 202-205 at the most. Those temps seem pretty good considering the factory stat. Those temps you have were what I had before the new Tstat. Those temps only fluctuate a degree or two with a/c. City driving in Florida.

 

dave when i sink my truck every weekend on the drive home it can get up to 215 when its covered in mud... clean it can hit 207 when fully loaded. i have a 180 thermo im putting in though so that will all change.