620 thermostat

I am having an overheating problem on my 620 that I think may be thermostat. Has anyone got suggestions on removing and replacing? I have owners manual and shop manual and neither are helpful. It appears grill, steering shaft and hood have to be removed to get to thermostat...is this true?? Thermostat housing papers to be connected to a solid water pipe, how can you get clearance to slide it back to remove thermostat?
 
I unbolt the water connection on top of the block to get the clearance you're asking about. Four bolts there - you'll need a gasket for that connection, a gasket for the thermostat housing, and two new O-rings for the water pipe. You can put the old thermostat in a pan of water and heat it up to confirm that it is stuck. It's nice to know that you're actually fixing the problem. I like to check the new one too before I install it, although I've never found a dud - yet.
 
Thank you for this information, that looks like a better plan. Can I (after unbolting at block and thermostat housing) slide entire pipe and housing back as one unit, and not have to renew o-ring connections?? If not, can I get o-rings at NAPA, or are they a John Deere part?? Thank you for all info... Dan..
 
(quoted from post at 13:37:19 06/24/18) Thank you for this information, that looks like a better plan. Can I (after unbolting at block and thermostat housing) slide entire pipe and housing back as one unit, and not have to renew o-ring connections?? If not, can I get o-rings at NAPA, or are they a John Deere part?? Thank you for all info... Dan..
Some digging through the parts shelves here has located a NAPA part number . 357-180 and 33388 should spec a 180F stat . The ideal temperature how ever is achieved with a 195F stat.
 
Dan, I've never tried to preserve the old O-rings. They are available from John Deere, and I don't remember them being expensive. It would be a perfect time to replace them, and clean up the water pipe ends.

I use a 180 degree thermostat in my 630, and it came from the local auto parts store.

I just looked at the parts manual, and notice that I failed to mention the O-rings on the bypass tube. You should plan to replace them too.

The large O-rings (2) are part number F3450R
The small O-ring at the water pump end is R375R
The packing washer at the thermostat housing is A5322R
The gasket at the block is A2376R
The gasket at the thermostat housing is F1781R

Here?s the prices from JD Parts:
(2) F3450R - O-RING $4.46 each $8.92 total
(1) R375R - O-RING, PACKING $1.13 each $1.13 total
(1) A5322R - WASHER, PACKING $6.40 each $6.40 total
(1) A2376R - GASKET, CYLINDER WATER OUTLET $6.76 each $6.76 total
(1) F1781R - GASKET $6.19 each $6.19 total

Total $29.40 USD
 
PJH, thank you so much for the research and info..I feel more comfortable digging into this project now..(Hay time now and the 620 is my tedder tractor, so it needs fixed now)... Dan
 

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