Well certainly I'm delaying the inevitable (removing rad) but I think the fan clutch is bad on my D1. I've read through a lot of posts on the subject but what is weird is my fan is very stiff to turn when cold but if I turn it a few times it spins more freely and I can get a couple complete revs. When the engine is nice and warm (and running), the fan will turn several revolutions after ign is killed. I can hear the fan cycling when the eng is warming up but once things are at op temp the fan doesn't change its tone or speed at all.

I've already got the fan out and clutch seperated. I'll try the chevy clutch and hope that makes the difference. I'm not too hopeful though as I nearly overheated on the drive home from the exhaust shop with OAT just 25 deg F. It also won't idle very long without getting scary hot. Although the electric fan has only come on a couple times even with the temp gauge above the hot line. Only fan that seems to work is pass side. I can't get the other fan to turn even with A/C switch on.

I pulled the t-stat and checked it. It was a bit erratic on the stove so I got another one. The replacement was even worse and it wouldn't even start to open until 195. It wasn't fully open until 210. This was a 180 t-stat! I took it back and also bought some rad flush and ran it today without the t-stat. I could only idle for about 8-9 min before the gauge started getting into the 'nervous' zone.

Regarding the gauge, it is very quick to come up to the 9 position (even from stone cold), stays there for quite a while then takes off for the red. Odd. I guess this is really the excuse I need to buy an IR temp reader.

Sorry for the ramble. Thanks guys. Matt

 

Your fan clutch is bad.
Your truck will overheat at idle if the fan clutch is bad.

 

I agree Spike. Now I'm more worried about the overheating at speed. At least this is a quick thing to try and it comes in and out easily (also obviously needed replacement).

 

At speed with the AC fans on on level ground it prob won't overheat while driving. When going uphill or at a stoplight, the temp will climb. I did everything including rad rodded, water pump etc and with AC on, 118 here in AZ at a stoplight I watched the temp gauge climb. I even checked the FC before but I knew I should have changed after I took ownership. Now no issues and if there are, I'm looking at a HG.

Long winded story aside, change it HH.

 

1. Take the single wire off the gauge coolant sensor. Gauge should read low. I wire brushed my sender, and now gauge still has same 9:00 area temp when warm, but starts out much "colder". I guess the grime build up was like a parallel resistor, adding a little extra reading , in my case at the bottom. So mine takes longer to get to the 9:00.

2. I've run mine with no stat, in summer the coolant temp will be 135 - 145. Were you overheating from repair shop in 25F with no stat?

3. If original radiator not flushed, sounds like a place to start, or take to an indy rad shop. A sludged up restricted radiator won't cool engine, even if it is cold outside, and would also have the hot to idle problem. If flush does not make a big improvement, may need rod out by shop.

4. One of your electric fans is just dead. There's a write up in tech area of a replacement Denso motor for it. Try finding Z109, condenser fan diode, if bad, it keeps electric fans from following inside fan switch.

 

Thanks SB. I removed and thoroughly cleaned the sender and its connector during the HG job. I'll try pulling the connector to see how it affects the gauge.

No, the overheating (according to the gauge) was with the original t-stat still installed.The vehicle didn't smell feel or act 'hot' in any other way (although the elec fan was running). I was going to take it for a spin today with the t-stat out but something else came up. I also had the fan removed by then. That doesn't scare me much (running without the fan), especially with our cool temps and lack of traffic!

Like I stated at the beginning, the rad is likely coming out. I just don't want to deal with the mess with all the cooler lines, etc. We have a good local shop that I'll likely take it to.

The elec fan issue is a pretty low priority but thanks for the resource.

 

When removing rad, there will be two oil lines on battery side, and two tranny lines on driver side, and some o rings. Have rad shop also test flow (or you can) of the oil / tranny coolers, I had a used radiator that had the oil cooler 95% obstructed and my oil light would not go out. While I was under the hood checking for leaks as it warmed up!! RAVE sheet attached

You can drive with no fan, don't stay stopped for a long time and keep eye on temps.

 

Being it is a copper & brass radiator, once you have it out, lay face down with tubes in the air. plug two small ones (overflow and return from thriottle body heater), and you can do some flush yourself. I poured in muriatic acid (brick washing acid, $7 at home store). Don't try this with aluminum radiator, it will dissolve the aluminum. Let sit 30 minutes, then flushed out reverse direction - all kinds of gunk came out. But considering the environmental disaster that must be taking place in your basement, and the low temperatures, perhaps a shop with hot acid flush is the best way. Even after my home brew acid flush I still had to do the rod out. Of course, even if you don't acid flush you can use a garden hose to gauge water in - water out flow.

 

I suppose if I do one side at a time I can catch most of the trans fluid and oil. I just see a big mess as the fluid(s) continue to weep and puddle...

 

Since oil and tranny are zero pressure at that point (engine off) not so much drain. Sometimes in blister pack aisle of parts store you can get rubber covers that allow you to block off an open nipple. Could put over line when disconnected. Or just a short piece of rubber hose from in to out.