Well with the weather as hot as it has been I've noticed that the temp gauge starts creeping up when the vehicle is stationary with the AC on. Yesterday it started warming up on my at 50mph with the AC on. Temp drops down to normal level immediately after turning off the AC. I have replaced the thermostat, checked the coolant level, and cleaned between the radiator and condenser. Condenser fans are working properly. Anything else to look at before I pull the radiator and get it rodded?

 

Water pump? Are you losing any coolant? I had the same prob, changed out my tstat, had to change the water pump as it decided to blow, of course I broke a bolt off and had to get it tapped out. Flushed my rad. Before the pump went, after the t-stat change and flush, it ran where it was supposed to.

 

Haven't checked the water pump. Not leaking any coolant though.

 

How many miles CU on your d1? Try the rad flush. Feel the water pump pully and see if there's any play. If so the bearings going out and not moving coolant properly.

 

145k. I did a cooling system flush last year. Gonna have the radiator rodded and cleaned, can't hurt. Hopefully the water pump is up to snuff.

 

Can't believe no one has said it yet... fan clutch.

Had the exact same problem and found my clutch was leaking fluid and not working as it is suppose to.

There are piles of threads like this on here. Suggest you search first if you have any more questions (like how do I check it, how do I remove it, etc.)

My temp gauge needle doesn't even move now in 90+ degree weather with the A/C on and parked. You can once again hear the roar of the fan - hadn't hear it in a long time.

 

About $65 for rod out at indy shop in my area, try to find one that works on tractors and heavy equipment. Be sure fans are blowing correct direction , toward the engine. My PO wired replacement fans reverse polarity, and would over heat whenever AC on and slow or idle. Test with plastic bag in front of grill, engine not cranked, AC on (fans should be running) - bag sucks toward grill. Same when truck cranked. Also check you main fan clutch. When warmed up, fan should spin, but not a whole turn. If it free wheels, the clutch is gone. Tech section has write up on $50 Chevy unit, which works great. When cold, the fan will roar when first started, because it is moving more air. Spinning it when cold should only turn a fraction of a turn.

 

But if overheating at 50 mph, it ain't the fan clutch (unless fan blades are on backwards). Want to test this theory? Hold a pizza box outside the window at 50 mph. I had a wobbly water pump pulley (bad pump), removed my fan and clutch, drove 30 miles home, no problems. Just don't stop for long periods. And if water pump failure is about to happen, better to have fan in the back seat than coming through the radiator or hood. I'll bet on the radiator, hope when it is resolved we get some follow up. But it is always free to check the fan clutch, you are typing with the required equipment.

 

Fan clutch is less than a year old. Gonna inspect the water pump and pull the radiator and have it rodded out. Local shop wants $50 bucks. Figure its worth it. Hopefully a rodded and cleaned radiator, a cooling system flush and fresh coolant and a bottle of Water Wetter will rectify my problems.

 

Good luck CU, I'll be following you on the rad rodding as everything else has been changed out and it's still getting warm with the A/C on parked after a bit.