4020 (Late 60's) Idle Speed

DT444T · Jan 10, 2010

I've got a late 60's (earlier model with dash controls) 4020 Diesel. We've had water pump and cooling issues and manually make it idle at about 900 RPM minimum to ensure cooling.

Does anyone know what the idle speed SHOULD be for this tractor? It normally idles about 600 RPM.

Any info would be great
Thanks,
Jake

RickB · Jan 10, 2010

I no longer have a 4020 op manual, but I think 800 will be very, very close to spec. 600 is low, I'm quite sure.

jd110 · Jan 10, 2010

800 rpm is spec for these engines. Are you overheating when idling? That seems unusual. Are you trying to run something with hydraulics or pto at idle? Have you had the radiator checked out? Radiators can clog internally and not allow the proper coolant flow. I assume you have replaced thermostats?

jenkinsph · Jan 10, 2010

It has been awhile for me but 800 sounds about right, I was suprized how much faster my 820 runs at idle (about 1000 to 1100 rpm). I never had problems with my 4020 overheating even when pulling a chisel plow in the summers in Mississippi. I would suspect considering the age of the tractor that your radiator needs rodding out.

DT444T · Feb 5, 2010

Thanks.
I do think that the radiator has been cleaned, rebuilt, or replaced (wasn't there at the time). Don't know about the thermostat but if it was bad I would assume that it would overheat every time it ran, or run cool at all times depending on the position that it stuck in. It only gets hot on occasion. The only accessory that it has constantly is the loader which is hooked to one of the rear hydraulic outputs.

Anyone know how to adjust idle?

Also, the PTO doesn't stop when it's off. It sort of freewheels with enough force to turn a Kuhn style 9ft hay rake sometimes (slowly) and also an auger.

I'm at school, 1200 miles from the tractor, but I'm trying to help my dad out who probably couldn't use "the computer" to save his life.

RickB · Feb 5, 2010

A 4020 diesel has two thermostats.
IIRC, idle adjustment is made at the injection pump.
PTO brake adjustment is dependent on transmission type; SyncroRange tractors may be just a linkage adjustment. Or the internal PTO brake may be shot. I never fussed with a Powershift.

jd110 · Feb 5, 2010

The angled screw on the injection pump is the one to adjust the idle speed.(beside #24 in picture) It takes a 5/16" wrench to loosen jam nut and adjust. Screw it in to raise idle speed. If you have a powershift transmission, check the linkage under the dash. Remove the kick panel between your legs and look in the lower left side. Lever#13a or b in drawing usually gets loose or worn where it attaches the control valve. It uses a 7/16" wrench to tighten it.