Today on my way to work, it was pretty hot. Maybe 90 degrees or so. While I was basking in the coolness of my new cold a/c system, and listening to the half broken radio that's in the 2000 Bravada 4.3l w/ Smart trac I just got, I feel a surge, more like a slip, and the rpms jump a bit. I'm not too surprised, I was thinking that knowing my luck with automatic transmission it wouldn't be long before I got one when it was about done with it's life. But what I saw next was the most shocking part, the coolant temp gauge jumped, went below where it normally was, and then rose back up a little and settled where it normally sits. On my way home, I had some more time to play with the truck and I noticed that it seems to be based off of the load of the motor. For example, if I have it in neutral or park, and I hit the gas, it will move, but just slightly. Pretty much what you would expect for a water pump that runs off the belt. When there is a load on the engine, like dropping a gear, or medium/heavy acceleration, it will fluctuate by about 50 degrees on both sides of where it normally sits. I'm thinking that maybe the water pump is going bad? Maybe the belt slipping or something? The whole situation seems odd. The more I think about it, I did remove the belt to put the new compressor on, and maybe the belt is causing the water pump to slow enough to maybe let an air bubble hit the coolant temp sensor... That wouldn't really explain the power loss or whatever though... These engines are cap and rotor or does the ignition run off the belt too? Anyway, thanks in advance. It doesn't seem like the truck is getting very hot, but I can smell some coolant from the front of the engine bay. Regardless if it's a major problem or not, I need to do a flush because the prior owner had some coolant work done at some point recently, and it was done half a**ed. Easily seen by the gobbing of gasket sealer on what looks to be the tube going into the top of the motor with the thermostat in it, and the evidence of fresh coolant still sitting in a little tiny puddle to the right side of it.

Anyway, thanks all in advance. Any and all input is welcome.

 

I'm thinking on my next day off I'm going to pull the plugs and take a look at them. Chances are they are older than the cap and rotor, so if they are bad, it isn't going to hurt anything to give the truck a tune up. That MAY eliminate the missing/slipping problem I'm thinking...

 

I'm starting to wonder if there is a ground problem. At first I was thinking maybe the transmission and gauge were going at about the same time, but now sometimes on takeoff it happens as well. Just like the engine shuts off for a split second. I'm thinking it could be a ground issue due to the needle indicating the coolant temperature basically bounces off where it sits when the engine is off. Is there a ground in the vehicle that goes directly to the ignition and that coolant tempt gauge?