Hey guys- kind of scratching my head with this. I have a 97 D1 with about 95k miles.

This summer I had a fluctuating dash temperature gauge after a long road trip. Took the truck into the shop and also told them I have been hearing the waterfall sound behind the passenger side dash. Asked them to pressure test the coolant system and check heater core.

Was told everything was fine following replacement of fan clutch- pressure ok, no coolant leaks or anything dripping out the bottom of the truck. I was told the insides of the heater core likely collapsed but wasn't leaking. This didn't really make sense to me (limited technical knowledge of cars in general), but the truck ran great and I could run AC, while driving 70+ mph up hills, etc no problem.

Now, since winter is coming i have run into a new issue. While driving with the heat on I noticed that the temperature gauge in the dash start to climb above the 1/2 mark, but instantly goes back to normal when I shut the heat off.

any ideas??

 

the dash gauge is useless and inaccurate. get a OBDII reader/scangauge/ultraguage or whatever. i have a real temp gauge wired in my 95 and have recently been seeing my dash gauge drop to 1/3 of the way up while driving and my actual temp stays steady at 180F.

 

had this issue on my 98, its a ground issue , clean all your grounds

 

X2 regarding the grounds, having just gone through this. Specifically, the grounds behind the LH and RH footwell side panels (E200 and E201 in the Rave electrical manual), and the grounds under the hood on the inside of each fender well, one by the ECU and one by the airbox.

The waterfall sound is air in the cooling system, and you're hearing it in the heater core. Classic Brit engineering, the heater core is the highest point in the cooling system. Go through the bleed procedure with the front passenger wheel up on a curb to ensure that the corner of the radiator with the bleed cap is the highest point in the cooling system.

 

Thanks for the info on the grounds locations that helps out a lot. I'll report back once the issue is fixed (hopefully).

 

the dash gauge is useless, and is merely there for decoration. for 60 bucks, get yourself an ultra gauge and install it permanently so that you can get an accurate real time reading of the engine temperature.

 

Clean the battery terminals, remove neg cable and clean the tabs and areas it bolts to body and frame, I also added a growing from battery to rad support and battery to engine

I never had correct voltage till then

 

good info, I remember you added some grounds, but could never remember exactly where you did it and have been wanting to do the same. what gauge wire did you use, and where did you attach the ground on the engine?

 

I had a small braided ground lying around, from batt to the accessory on engine closest to batt, just undo a bolt

Other was a thin ground wire I had around

 

The 'waterfall' sound from the heater core could also be a tell-tale sound of a mildly leaking headgasket. I've had a few cars that had such sounds for several months ..and one day the headgasket finally let go. Heads redone and new gaskets and sound never came back. Not uncommon. Sniff in the resivor for combusted gases. Do a check with strips. Is your rig using any coolant?