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Hi everyone,
My MH was in a camping last 3 months and I took the road last weekend. After 2-3 miles, water temp was 280 (red light). I stopped as soon as I can, add coolant (it was not completely full) and let the engine runs for 3-4 minutes. Temperature decreased to normal (I don't remember exactly what temperature but gauge was at "12 o'clock") and I took the road again. Unfortunately temperature increased after a couple of miles, oil pressure was also high (red light) so I stopped the vehicle definitively and have it towed to my brother's house (no garage in the area wanted to take it!). At this point, radiator was still full of coolant so it does not seem to be a leak problem.


This morning, with the engine cold (water temp gauge was at its minimum), we started the engine and temperature increased immediately to 280 again. We think the problem could be the temperature sending unit. Other things to check before replacing this unit?

EDIT: just noticed there is another water temp gauge at the back of RH (rear right compartment, near another oil pressure gauge and oil level). Water temp on this gauge is 215-220. Can it be trusted as the real value? Is it too high anyway to take the road ? I've read here a comment made by Mel in 2014 that says that "normal operating temperature for the engine is 190 to 215 degrees Fahrenheit"

Thank you for your help
Regards,

Patrick
Safari Sahara 1996
CAT 3126, serial number 1WM01549

Some time ago I had a similar problem. Replaced the regulator - thermostat - it was physically broken. Cat says to replace every 3 years. Is your radiator clean.

Also check that the V belt that drives ONLY the water pump is in good condition and properly tensioned (it is not on an automatic tensioner).

Checked the belt and it seems to be good. The water temp gauge at the back shows value in the normal range (little bit high though): 215-220. The water temp gauge at the front always shows 280 after starting the engine (even after hours being cold). I could make wirings from the back to the front if I can be sure I can trust the gauge at the back. How can I do that? By the way, are the 2 gauges on the same circuit or not?

Patrick
Safari Sahara 96
CAT 3126

Actually there is 2 senders on the regulator( thermostat) housing next to each other and each is used for 1 only. I spent a frustrating hour or two with my big hands and reached under the CAC pipe and between the alternator and regulator housing to carefully remove the sending wires and swap them over from front to back gauges. I may have also removed the serp belt and loosened the alternator and tipped it out of the way. Fuzzy about the details as sweat was dripping from my forehead and a few choice words were being mumbled. Worked for me as now I know that the sensor was/is pooched and I own 2 new ones for another rainy day project but the front dash gauge is in normal range and the back one.....well I can't run fast enough to see if it works at highway speeds

Suspect you have around a 190 degree thermostat(s) called regulators by Caterpillar.

So even 215-220 unless long hard climb is too high.

Have you cleaned the FRONT of the CAC? Checked it with a strong flashlight to verify the perimeter, particularly lower perimeter is as clean as the center?

Thank you Brett, I will do that. Meanwhile, can someone tell me the part numbers for the 2 TSU and for the thermostat? I've seen CAT 3126 thermostats that are 190, others are 177 degrees.
Regards
Patrick
Safari Sahara 96
CAT 3126

Any Caterpillar dealer can look up the proper parts with your engine serial number.

MUCH better than guessing or having Bubba at a parts house give you his "wisdom".

It will also insure that you get quality parts, not "made to replace" parts of unknown quality.

Just not worth the risk of ruining an engine for a few bucks.

You can go to --> https://parts.cat.com and look up the part numbers yourself. You have to put in your engine serial number to get results.
I did this with my serial number and came up with 2 different thermostat part numbers. However, the description does not say the temperature spec for either one.

Here is my .02 on how useful CAT is by calling them

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