Temp Gauge Reading

[JFitzgerald]

Along the lines of the thermostat post going now, it got me thinking about my temp gauge. While towing about 12K on vacation last week in the 95* heat with the AC on, my gauge was reading higher than normal (no surprise). Normally, unloaded, it runs on or slightly above the first mark, which is about 1/3 of the scale. It was up to about half or a bit more on most of the hills. I don't think it was a problem, but would like to know where I'm at.



I'm not sure what is "too hot". The factory gauge is not marked with any color or anything indicating "too hot". Just the typical "dummy" C & H. Does anyone have an aftermarket gauge so you know about what the stock one is telling you? Also, what temp is too hot for the Cummins?

 

[Case500D]

Temp

John,



I think the owner's manual says that straight down is okay to run under a load. I would start to worry if it went to the right of the second mark. I have noticed a difference in my truck if I just take the garden hose and flush all of the bugs, grass seeds, dust, and other accumulated crap out of the radiator fins. Good luck.



Jeremy

 

[JFitzgerald]

Jeremy,



Hadn't thought of looking in the owners' manual. That would be too easy. Thanks.



There are three more gauges I'd like add - tach, coolant temp and oil pressure. Just so I know what the real numbers are.

 

[Bill Stockard]

Jeremy,



I had a Horton fan on my '92 D350. The Horton would cycle on at 203-205 degrees coolant temperature. On the gauge, it would be a couple of needle widths to the right of straight down. I was nervous the first few times I towed with the truck to see the gauge go that high, but over time I got used to it.



The higher temps of 230-250 degrees won't hurt your engine. The problem with the higher temps is coolant boil-over. When the coolant boils inside the engine, a hot spot develops since cooling in that area is lost--steam absorbs less heat than liquid coolant. The engine needs to operate at a safe margin below the boiling point which in the pressurized system is below the 230-240 degrees.



Bill

 

[JFitzgerald]

That's good info, Bill. Now I feel OK on coolant temp. That was probably the worst case towing for me. 95*+, humid, AC on, pulling 12K in the hills of southern IN. The only time it might be worse is if I take a trip through the moutains with the same load, which I plan to do.



I did take a look at the radiator, and it could use a good flushing out of bugs, etc. I'll hose it out.



Now, I need to get my EGT's down... The truck did great, but it was real easy to get the EGT too high on the hills. Had more pedal, but couldn't use it.

 

[Bill Stockard]

I made a tool to blow out my radiator with compressed air. I took a long brass tube about 1/4" in diameter and put a 90 degree end on it so I could run it down between the intercooler and radiator to blow out the bugs and debris. I found that if I "soaked" the bugs with water from a water hose first it was easier to flush them out with the compressed air.



On your high EGTs you might try running in a lower gear at higher RPM and see what that does to your EGTs. In a lower gear, there is less load on the engine and the EGTs will come down.



I towed a 10,000 5th wheel trailer all over the US with our '92 D350 automatic with a 3. 54 ratio. I ran in direct(3rd gear) a lot--more cab noise, but the temps stayed down.



Bill

 

[JFitzgerald]

I flushed out the radiator & condensor with the garden hose this weekend. I did the intercooler some also, but access is not good. The AC seems to be cooler now, so I'm sure it helped. Looks like the radiator would come out real easy. I may pull it so I can wash it out real well and get access to the intercooler too.



About the rubber flap that goes across the top front of the radiator - I imagine that Dodge put it there to keep hot underhood air from short-circuiting through the top of the radiator and to direct air from the grill up there?? The flap on my truck is sagging, and actually blocking air flow to the the top fins. This is mainly because of the suction of the fan when the engine is running. I can see it at idle, and I would guess it's worse when going down the road at higher RPM.



My thought is to add support to the flap somehow to stiffen the flap so it can do its' job, or possibly replace it with a stiffer material. I thought about removing it, but I think it's there for a good reason. Anyone else notice this before?