DK40SE Squeal - Tightening the Belt(s)

spindlewood · Jul 24, 2023

Please forgive what must be second nature to many.

My 10 year old DK40SE with about 380 hours is squealing on startup. It's gotten worse and is time to fix. I'm presuming it's the belt. It's coming from the front, it goes away when warmed up - although taking longer now. With only 380 hours, I prefer to see if tightening will fix the problem before getting a new belt.

I prefer good instructions to start. While, I've got the service manual, I can't find clear instructions.

First things first. Please correct my assumptions if I'm wrong. I can wield a wrench just good enough to be dangerous, but I am not a mechanic by any stretch of the definition.

There are two belts side by side. I presume the one on the left is the "fan belt" but I also see it referred to as the "A/C belt". Is it both or only called the A/C belt? The one on the right I presume is the "alternator belt"?

I also am presuming that it is the A/C (fan) belt that is squealing (both seem loose, but I'd say the A/C belt is the more obvious one).

What I presume is the A/C belt "tension bolt mounting nut" I've labeled as #1 in the attached pic. Is #2 the "tension bolt"? Do I simply loosen both bolts on #1 and then tighten the belt using #2 and finally lock in place by tightening the two #1 bolts?

Is this what you would try first? If I do need to tighten the alternator belt (if that is what it is), is it a matter of loosening bolt #3 in my pic and using a bar to put pressure on the alternator, then re-tighten?

Any advice would be extremely appreciated. Thank you in advance.

Billrog · Jul 24, 2023

Spray some soapy water on the belts and see if the squealing stops.

Harry in Ky · Jul 24, 2023

It's probably the alternator belt making the noise. Load on the alternator will be greatest when first started up. The compressor belt won't have any strain until you switch the A/C on. If the A/C is on, try switching it off before starting. If the belts feel loose before starting, tighten them up. If you can pull hard on the alternator fan blade and turn it with your fingers, it's too loose.

spindlewood · Jul 24, 2023

Harry in Ky said:
It's probably the alternator belt making the noise. Load on the alternator will be greatest when first started up. The compressor belt won't have any strain until you switch the A/C on. If the A/C is on, try switching it off before starting. If the belts feel loose before starting, tighten them up. If you can pull hard on the alternator fan blade and turn it with your fingers, it's too loose.

I will try the alternator belt, thanks.

I do constantly have the A/C on in the summer, so I'll try starting it without and switch it on to see if it makes a difference. Did I get the procedure correct with the A/C belt? Somewhere I read that it the play is more than 1/2" deflection, it is too loose. I'd say it's more like an inch.

Billrog said:
Spray some soapy water on the belts and see if the squealing stops.

I'll give this a try as well. I've seen it mentioned and from what I can tell, it can't hurt anything.

Harry in Ky · Jul 24, 2023

Belt adjusting is pretty much as you stated. The alternator might require loosening the bottom bolt as well before the pry bar portion.

Squealing compressor belt usually won't stop as time goes on. (It might stop if/when the clutch cycles off) The alternator load decreases slightly as the battery charges up and demand is reduced.

spindlewood · Jul 25, 2023

Harry in Ky said:
Belt adjusting is pretty much as you stated. The alternator might require loosening the bottom bolt as well before the pry bar portion.

Squealing compressor belt usually won't stop as time goes on. (It might stop if/when the clutch cycles off) The alternator load decreases slightly as the battery charges up and demand is reduced.

I adjusted the alternator and no squeal - but it had already warmed up and stopped squealing before. I'll know in the morning for sure. Thanks for your help. It definitely needed both bolts loosened. The bottom one seemed to be SAE and not metric. Strange.

I left the A/C belt alone. It made no difference turning off the A/C while it was squealing.

caver · Jul 26, 2023

Sometimes if my thigh hits the left speed lever just right on my DK40HST it kills the engine. This has happened several times recently as I was running the tractor pretty hard backfilling my foundation. If I don't reduce throttle to idle when restarting it squeals. I have a can of belt dressing but always forget to spray some on.