I have a 2500 GMC Duramax, 2006 model (diesel). It's my farm truck and we pull a lot of heavy things. Recently, we've replaced thermostats, water pump
(it leaked recently), cleaned air intake filter/new, cleaned out radiator fins, put on a new A/C radiator (heavy duty). Radiator was flushed out a year ago. Aside from things obviously easy to repair (and we repair everything possible), an issue for a couple of years is this: When we pull a heavy trailer, the engine
temp guage goes up (even on a cool day). Not pushing it much, I let off and temp cools to normal after a few minutes. After a few more minutes driving, when I need power up a hill (at normal temp), the engine cuts back and won't shift or gain speed. I suspect the temp/sensor kicks in the protection mode from getting up to 240+ deg. Mechanics (GMC and independent) say my trans is great shape (we had an oil seal last fall but it is good to go). However, it shifts somewhat rough when being aggressive acceleration. I have in the last 2 years/past replaced the gear shift (on the column) - which is the lever when you select Manual, D, N, R, P etc. Note that manual versus D (automatic shifting) does not affect anything, nor does trailer versus no trailer mode. One person suggested my radiator is restricting water so much that it overheats - we use Dex Cool all the time - so is that possible? Today we also checked radiator temps, and the output is 20 degrees cooler than input, we suspect thermostat, but they were just replaced. The sensor reads 10-15 deg. hotter than the water temp, so we think it could be sensor, but when not pulling, the pickup stays nearly constant on 200 degrees while driving (by the guage/sensor). When idling around and sitting it cools half way between 160 and 210 - is that correct or should it stay at 200/210? I thought the pickup always cooled back when idling on a cool day. In the hot summer, it stays at 210 idling/sitting. Oh, we tested the Dex-cool, and no exhaust
in the coolant
- so perhaps that rules out a gasket issues internally?