My John deere 420 W Engine overheats

twocylman · Jul 7, 2015

My radiator fins are clear, fan works and belt is tight. The engine block overheats after about 15 minutes or less of field mowing. I took the hose off of the top back of radiator and took coupling above water pump apart. There was no thermostat at all, Was there suppose to be ? I have mowed with this tractor for 25 years and never had a problem till now. Any suggestions on what could be causing the engine to get so hot so fast, and I can take the radiator cap off and it never boils out or steams ?

gene bender · Jul 7, 2015

If with the cap off and it doesent boil out what makes you think its running hot.

dzc3 · Jul 7, 2015

Check the temp gauge I have worked mine HARD and can't get it hot. This tractor had a good size radiator, for the engine it was cooling. The fact that you have used it all these years and now it runs hot seems odd. No bubbles in the antifreeze when it running?

dustycoal · Jul 7, 2015

Check the exhaust shield, Mine was letting hot air in on temp switch and ruined the switch wiring.

Mike M · Jul 7, 2015

How's the ign. timing ? maybe it changed from where it was ?

twocylman · Jul 7, 2015

(quoted from post at 03:16:25 07/07/15) If with the cap off and it doesent boil out what makes you think its running hot.

# 1 the water temp gauge is buried, and # 2 the tractor starts to lose power, run rough and when shut off, it diesel's a lot.. Plus , I let it sit for an hour and a half in a shaded area, and the exhaust manifold was cool, but the engine block was still very hot to the touch. It took hours for it to cool down.

twocylman · Jul 7, 2015

quote="dzc3"](reply to post at 03:31:10 07/07/15) [/quote]
No bubbles in anti freeze

JRSutton · Jul 7, 2015

The engine running rough COULD be a coil problem - or less likely - a valve clearance issue.

If it's not blowing steam - I'm also guessing it's not overheating.

Not sure how those tractors are wired - but if you can pull the sender and stick it into a pot of water of known temperature, you might be able to clear up the question there without spending any money.

Dick2 · Jul 7, 2015

I think that they were made that way at the factory.

rbhuntn · Jul 7, 2015

(quoted from post at 08:34:30 07/07/15)

(quoted from post at 03:16:25 07/07/15) If with the cap off and it doesent boil out what makes you think its running hot.

Click to expand...

# 1 the water temp gauge is buried, and # 2 the tractor starts to lose power, run rough and when shut off, it diesel's a lot.. Plus , I let it sit for an hour and a half in a shaded area, and the exhaust manifold was cool, but the engine block was still very hot to the touch. It took hours for it to cool down.

I know this may sound like the simplest and stupid thing, but here goes.

Had a friends tractor that started running hotter than normal. Coolant level was fine and good green color due to being changed last year. Found a screen just in front of the rad that was clogged with grass, cottonwood fluff and other stuff from the field. Cleaned that screen that allowed better air flow and it now runs well down below the half way mark on the temp gauge.

Have seen this one being overlooked a few times. Just a thought.

BJ

twocylman · Jul 7, 2015

(quoted from post at 10:56:16 07/07/15)

(quoted from post at 08:34:30 07/07/15)

(quoted from post at 03:16:25 07/07/15) If with the cap off and it doesent boil out what makes you think its running hot.

Click to expand...

I know this may sound like the simplest and stupid thing, but here goes.

Had a friends tractor that started running hotter than normal. Coolant level was fine and good green color due to being changed last year. Found a screen just in front of the rad that was clogged with grass, cottonwood fluff and other stuff from the field. Cleaned that screen that allowed better air flow and it now runs well down below the half way mark on the temp gauge.

Have seen this one being overlooked a few times. Just a thought.

BJ

Click to expand...

Thanks, BJ, but I checked that too. Air flow is well in front and behind radiator . My muffler was really bad , and was getting soot all over gas tank, I changed it , so as soon as I get it back together, I will see if that helps. Those green JD hoods attract heat from the sun something crazy. I am sure that does not help matters. It gets so hot , (the hood), I can't put my hand on it for balance when getting on and off tractor.

Matt Thomas · Jul 7, 2015

I know your 420 is newer than my MT but just thought I'd toss this out there. My MT has no water pump and I didn't think the 420 did either...but I was wrong once before. If you added coolant.....or changed the coolant.....without premixing the water and antifreeze....that can sometimes (but not always) cause over heating in JDs with that famous "heat siphon" cooling. Something about two different specific gravities.

twocylman · Jul 7, 2015

(quoted from post at 13:06:25 07/07/15) I know your 420 is newer than my MT but just thought I'd toss this out there. My MT has no water pump and I didn't think the 420 did either...but I was wrong once before. If you added coolant.....or changed the coolant.....without premixing the water and antifreeze....that can sometimes (but not always) cause over heating in JDs with that famous "heat siphon" cooling. Something about two different specific gravities.

Ok, everyone, I think I fixed the overheating problem. Here is one to keep on record in case this ever happens to you. First, I took off the large hose on bottom of radiator , and then took a garden hose from a high output residential hydrant. I turned it on full blast and the water was coming out full force at the bottom. I also had the top hose on the radiator off at the same time. I blocked the water from coming out of it. Then, I put everything back together. I did "NOT" install a thermostat. It ran for years and years with out one, so I left it out. Here is the thing that cleared up the problem. My muffler was really bad, was shooting out soot all over the heat shield ,and fuel tank. I think the super heated air coming out was the cause of the problem. Also , when I super flushed it, I may have also unblocked a possible clog. I started the tractor , let it run a bit, then I took it and mowed my lower field with it with a 5 ' bush hog. I worked it hard, and guess what ? It ran like a top, and never got over 170 degrees And this was running it on straight water only. When I was through, just a tad of water came out the top when I removed the radiator cap. I am going to give it a 50/50 mix of water/anti freeze, and change the oil. (it's due) My head gasket did take a strain because of the heat issue, there is a slight seepage of oil around gasket. Oil pressure was always high however. If your engine overheats. Check muffler, and flush radiator like I did. Thanks all of you for your suggestions !!!

My John deere 420 W Engine overheats

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gene bender

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