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rkainsworth · 04-09-2017, 04:12 PM

Driving in W. Texas headed to New Mexico. Noticed my temp gauge needle floating between the A and L in "normal" range. Pulled over and put Scan Gauge on water temp. Here is what I saw: much of the time temp was between 200 - 204 range. Going up slight incline it would climb to 205 - 207. Then back down to 202. On longer slight inclines the temp would rise to 210,11, even 216 once. At higher temps I would pull over and let it cool down. I am driving at 65, hauling a small car and outside temp is 90. I am assuming I have a problem, right? Any suggestions? I am not opposed to using a truck repair shop in the town I am in. What is normal temp range for this engine? At 216 I was almost in the red spot of normal range on gauge. Any help would be appreciated. There is 91000 K on the engine.

Rich

rkainsworth · 04-09-2017, 05:02 PM

This is a 5.9 ISB engine

MnTom · 04-09-2017, 07:46 PM

Yes, I think you are running a bit warm. I would expect to see 180* to 200* or so. Have you ever cleaned the radiator? Some motor homes have a problem with the radiator getting plugged. Get yourself some simple green and clean it out good. You just may be surprised as to how dirty it is.
Does your fan kick on when it gets hot? You may also have a fan controller issue too.

jimmy braden · 04-10-2017, 09:07 AM

Yep, Rad clean and maybe a good coolant flush (along with a new thermostat). Id recommend keeping the speed a little slower - what Rpm is it at 65? Id say if its more than 2200 your loosing mpg.. You might need the rpm to keep coolant flow up until you get a little more insight into whats going on.

Diesels should really stay at most 200. Ideally 190-200 to give you some headroom.

You got more hills coming up on this trip?

rkainsworth · 04-10-2017, 09:48 AM

Ok, checked with Cummings: recommended maximum heat is 212, so I do have an issue. Called Good Sam Club gave me the name of a repair shop 2 miles from my location, waiting for them to plug in and analyze.

Wayne M · 04-10-2017, 11:22 AM

How are you going up the grades? Are you WOT (Wide Open Throttle)?

I have the ISB also. When going up grades I watch the temp indicator and if it starts rising above 205 I drop down a gear and keep the RPM's at 2000. Works every time. I have been up to 217 and dropping down a gear and RPM's at 2000 dropped it back to 205-207 real quick.

Another trick, when you see the grade coming apply foot pressure to the accelerator pedal until you reach you present cruise speed. Take it off cruise control and never move your foot (don't accelerate, don't decelerate) and still watching the temp gauge let the motorhome transmission do its job. If you do notice temperature increasing above safe level, manually drop it down a gear and get the RPM's to 2000.

Works for me every time.

p.s., you may go up a grade at 25 mph but you'll go up below max temp allowed.

rkainsworth · 04-11-2017, 02:17 PM

Okay, made the big decision to replace the radiator! Turned out to be a great decision , the radiator was crumbling as you merely touched it. Glad to get it done before heading into unpopulated mountain regions.

panheadpaul · 04-12-2017, 09:16 AM

03 Monaco 400 isl rad fins coming apart no hot air from lower sectin of rad side mount hot at top warm in middle blew out with air & pressure washed , need rad soon , lower gear & speed keeps it about 200 deg

RVThere · 04-12-2017, 11:11 AM

Quote:

Originally Posted by rkainsworth

Okay, made the big decision to replace the radiator! Turned out to be a great decision , the radiator was crumbling as you merely touched it. Glad to get it done before heading into unpopulated mountain regions.

I changed the radiator last summer with about 100k on my ISL. Shop said the radiator looked like a blackboard inside with no air flow!

Since they had the rear radiator out, I had them replace a number of items including idler pulley, water pump, etc. Runs like a champ now!