I have noticed that my stone cold motor, even in 30-40 ambient temp is getting to operating temp quicker than it has in the past.It never overheats but can get as high as 198-199 even in cold weather. have been running a rover 180 tstat for years as well as the Hayden 2991 clutch. No coolant loss.


I did notice the other day that the usual loud air moving noise that the Hayden 2991/fan makes at startup was not present and when I got home last night I popped the hood and I could practically spin the fan with one finger.

I have a spare NIB 180 stat ready to go but that fan clutch now has my attention. It should be locked up when hot at the very least correct? And with it not moving air like it used to at start up I am thinking there is a problem.

thoughts?

 

fan clutch is your issue for sure.

 

Sometimes, gunk leaking out of the fan clutch, front or back is a sign of failure.

 

Well I swapped in a new fan clutch with no improvement. Still getting up to temp pretty quick but again not overheating.

If it is a Tstat failing I’ve never had one be so consistent while doing so.

thoughts?

 

I don’t think failing t stats are that consistent. If it continues to stay at those temps as the weather heats up, I’d call it a non issue.

 

As we age, time seems to pass more quickly. When I was 2, one year was 1/2. Now one year is only 1/67.

 

I might have the same issue. What is the fan clutch supposed to be like? At cold I can also move it easily with one finger but still feel resistance. Is this not normal?

 

Some posters describe the feel as "peanut butter". It is hard for me to tell by feel since even a bad one has some resistance.

There are different specs depending on the clutch model. Hayden standard duty thermostatic clutches spin around 70% of water pump speed when hot, only 20 - 30% when cold, for fans with 1 1/2 inch blade pitch. Heavy duty clutches spin faster (up to 90%) when hot and really loud when engaged. But the clutches start out in the hot (engaged) position when first started in the morning. This puts more fan load on the motor and actually helps get up to temp faster (since the t-stat is still closed). Here is a test sequence. Start the truck cold and the fan should be very loud. Then rev up the engine 1500 - 2000 rpm and hold it steady until the fan noise fades away (good clutch function). This can take up to a minute or so while the silicon stuff gets rearranged inside the clutch. It should gradually get quiet and you will hear more engine sound vs fan sound. This test is for thermostatic clutches. Some cheapo clutches only spin one speed. The thermostatic models for Discos have a little bi-metallic coil on the front center.

If there is some silicon gunk leaked out on the clutch, and fan is quiet even when cold, then the clutch is kapoot. Fan clutches do wear out, so good to pay attention. The fan clutch operation can be heard while driving, with careful listening, especially during that first mile or so. After the first drive, the fan clutch can start out in slow speed (quiet) mode, if it is still below 170 deg F or so at the clutch. Hope this helps.

 

Walking on thin ice with hot feet, too may HG jobs under my belt to be taking that kind of risk.

 

what would you do to mitigate?