Hey guys,
1998 5.9L 4x4, 46re( I believe ) K&N cold air kit,
I have read a few posts about over heating issues. I am having the opposite. She's staying cold. I've changed the thermostat 2 times now, 1 of which was perfectly fine, it had not been fouled. The first thermostat was hooped from when i bought the unit, swapped it for a 180, this was before I read all of the useful info about thermostat temps. Never the less, even with the 180 installed the temp gauge hardly got off the first tick mark. So, after research here, I swapped out for a 195. It does get a bit hotter but it still only makes it maybe half way to 100 degree mark on the gauges. Canadian unit gauge is in Celsius. its my understanding that the reg. running temp should be around the 100 mark? So, today I put cardboard in front of the radiator. Like, completely. she ran juuuust under the 100 mark all the way to work, hour and a half drive. It started to climb a bit over the 100 mark when almost to work so I removed the cardboard, it was making me nervous. Immediately it dropped all the way back down to the first tick mark on the gauge and stayed there until I parked. I let it idle for about 15 min, temp hardly rose at all. There is heat. Not Hot like when the cardboard was in place but still heat.
The clutch on the fan does freewheel, When you first start the vehicle the clutch fan "sets itself " it engages and then it free wheels. Even after shutting the engine down the fan spins. I'm pretty sure the clutch is ok.

I read about a cold engine causing the computer to go into open loop mode, which hinders the mpg's, and a cold engine can cause other issues down the road, rather keep her in as good of shape as possible.

So, I'm thinking either my fan is moving too much air, the rad is too thick (one too many cores), or the temp sending unit is hooped.

Any other ideas on this issue?

 

Use a scanner, and a temp gun, to see just how accurate things are. On yours, I do believe there is only one temp sensor, and it tells the PCM what engine temp is. PCM then passes on that information to the instrument cluster, so it knows what to display. Take it for a good drive, then see what the scanner has to say about engine temp, and then the temp gun.... Are they even close?

 

Thank you sir!
Looks like there's a trip to the auto store in my future! I have neither of those. I only have a cheap code clearer.

 

Yeah, if you wanna work on these yourself, having at least a half-decent scanner is pretty much a requirement.

 

Well, got a new sensor installed and now it the computer is getting the proper temp. Big THANKS to " HEY YOU" for the tip. Much appreciated.
Engine is still running cold though. Mind you it has been -25C. But even in warmer weather, -7 to -10C it still runs cooler than where it should be, about 10-15 degrees. I've had to put cardboard in front of the rad to bring it up to where it should be running.
My thought is that the fan is pulling way too much air through the radiator.

QUESTION: I know the fans blades from the 2nd Gens have fewer blades, Would they fit in the shroud of a 1st GEN?

 

Is your fan clutch seized up? Don't know if the other fan would fit....

 

Has the timing chain ever been replaced on your truck? 290,000 kilometers is a little over 180,000 miles. I'd check your chain for slop. If it has jumped a tooth, the engine won't warm up. I replaced one in a 3.9 that never really got that warm and afterward it got hot and would roast you inside along with a substantial increase in fuel economy. Now, this was a 6 banger so you won't see as good a fuel mileage, but mine went from 17 mpg to 24 on the highway.

Put a mark on your harmonic balancer and remove your distributor cap. Make another mark on the distributor for the rotor (I use soap stone, do NOT use pencil). Rotate the engine backwards by hand. If it moves more than a few degrees, you may have a lot of slop. Sometimes you can hear the chain rattling inside behind the water pump. A home mechanic can do this but you want to do it inside up north as it does take a while and you usually need to crawl under the truck.

 

You could get an ELM327 bluetooth OBDII reader off ebay for $20 or so, then add the Torque app to your phone. You can monitor a lot of things while you drive. I've watched mine warm up for the first time after replacing the water pump. Very helpful. I keep a ELM327 in the glovebox of all my vehicles.

 

I have read this makes a huge difference. Actually I've creeped a lot of your previous posts in this regard. I do have plans to swap out the timing chain, I need a new front seal anyway. Everything you have mentioned here makes sense. My mileage is pretty terrible around 15-18MPG and I really try to keep my foot out of it, as I commute 1.5hrs one way everyday. I know, not exactly the best long haul commuter, but its great for those snowy blizzardy days in the mountains.

HeyYou,
It doesn't appear to be seized. It free wheels, but it does seem to move a lot of air before its even up to temp, but that could just be the clutch setting up. The clutch does engage when it gets hot though. I did an experiment...

JeeperDon,
That's a really good idea!! I never thought of that. Thank you!!!

Timing chain will be my next project!

Thanks everyone for the tips and advice! Truly appreciate it, I'll keep you updated!!

 

*UPDATE*
Well, swapped out the timing chain and sprockets, new 195 stat, upper/ lower rad hoses, fan clutch.
Definitely a huge difference all around.
Diagnostic tool is reading that the temp sensor is reading 181F at idle and sits around 183-185F while driving at 60MPH. It will hit 188 when making it work going up hill, I have some pretty long hills to work, about 3 miles up hill. My infrared thermometer crapped out and I was getting temp readings all over the place.
So I'm not sure if this the actual temp, but when it is idling and reading 181, the top rad hose is solid, which, I have been told, means the stat is open and allowing coolant through.
I need to replace the my infrared and know what temp its actually running at.
I guess my next question is, does this sound like a proper temp'd engine? Should it be running hotter?