JD 650 Overheating - 521 hours - thermostat replace?

[Edensgardener]

Hi everyone - I've been sort of lurking on this forum several years and always find great help - ya'll are awesome. But I had to finally post a question as I'm not finding the answer to this issue.

My little JD 650 started overheating last week. I replaced hoses (as I found a leak) and topped off with new fluid, and thought that fixed it. However, then I noticed "smoke or steam" coming out from under the "hood" and a very hot engine. Looked like diesel leaking through one of the copper washers. Bought 2 sets and replaced them all along with the remaining original fuel line tubing. I'd already replaced several of the others.

STILL overheating. So my next thought is that maybe the thermostat is stuck - however, I for the life of all 110lbs of me, can NOT budge either of the bolts on the housing whereby I need to get that thermostat OUT and put in a new one. Much less figure out how to put a new one in there. LOL

It seems the bolts are about 1/2", but not getting a tight grip with wrench. Next size down is too small. Is the Yanmar running metric sizes? Or, is there some trick.

Hoping and praying I've not overheated to the point of damage, but I don't think so. I shut him down as soon as the light popped on and/or I started to notice something wasn't right. You can smell it when the engine gets hot. No signs of cracked block, etc. Just can't run for more than 5 or so minutes w/o it running hot.

thanks in advance for all your expert advice! I'm going to head to the dealer and pick up the replacement thermostat and hope for some replies when I get back.

m

 

[Rock knocker]

Metric sizes

 

[Capricious]

Are the radiator "fins" plugged-up with dirt or other debris?




EDITED TO ADD: If you suspect the thermostat you can put the old one in a pot of water on the stove, heat it up, and check to see what temp it opens at, or if it opens up at all.

 

[Edensgardener]

I actually cleaned all of the fins, yes. Thank u. Considering the color of fluid coming out of the hoses, I am probably better off just replacing it - IF I can get in the darn housing!

 

[Capricious]

I actually cleaned all of the fins, yes. Thank u. Considering the color of fluid coming out of the hoses, I am probably better off just replacing it - IF I can get in the darn housing!

I will assume that you cleaned all crud out that was deeply imbedded within the fins, and did not just wipe off the crud visible on the outside. Cleaning has to be very thorough, but gentle. Radiators are fragile.

By "fluid" do you mean coolant? If the coolant is dirty-rusty-brown it is possible the radiator tubes (and maybe water jackets) are plugged, in which case changing out the thermostat won't do much good.

What is indicating that the issue is the thermostat?



EDITED TO ADD: Does this tractor have a belt-driven waterpump & fan? Is the belt loose and slipping?

 

[Edensgardener]

The fins weren't really blocked much at all, and with hood open I can see thru all of the holes just fine.

As for pump, yes, fan driven - not slipping. And yes, coolant.

How does one go about checking foor clogged tubes/jackets?

I changed most of the hoses, one leaked and one still orig JD green. .

I got the housing opened and dropped iin new thermostat. Letting it run in the barn for awhile to see if he runs hot or if this (hopefully) resolves.

 

[Edensgardener]

What I did notice, and maybe this is normal, but there's not any coolant in the side hose (large) coming off engine when I squeeze it. I would just have thought it would make a squishy sound as if there was coolant in there?

 

[Capricious]

I don't know if you can tell much about coolant flow by squeezing the hose.

Keep in mind that the thing might run cool @ idle speed, but still overheat when under load.

I am not aware of a good way to tell if the radiator core is plugged up, short of taking it into a radiator shop and having them look at it, at which point you might as well have them clean it out anyway.

How old was the coolant?

 

[Jerry/MT]

Make sure that the air supply is not restricted. if it is it will increase the fuel/air ratio and that leads to higher temps in the combustion chamber and reduced power output.

 

[Edensgardener]

I'm bummed. I thought I'd solved it with the thermostat change out, ran it about 20 mins or so under a light load, just some light disk work, and it was fine. Let it idle till I was ready to go out to the big field - still no problem.

Got it out there, started to disk an area with a bit more weed coverage and sure enough, after about 10 mins - I started to smell the heat and on came the idiot light - too hot. So I shut it down, popped the hood - nothing leaking, coolant at the mid level on the overflow. I even (earlier) rinsed out the fins - although there wasn't anything in them, I thought I'd knock the dust off the whole tractor since I was near the hose.

So from looking at the two above replies - I'm potentially looking at either taking the radiator off - that's going to be fun I can tell already - or see how there could be an air flow restriction.

On the latter, Jerry/MT, how would I know this? Fan is running, fins are clean, etc. I'm not probably familiar enough to understand what you mean.

Also, Caprisious, would it potentially help if I started by flushing the radiator - before I attempted to take it off and to a shop? There was good colored coolant in the top of the radiator this AM - I took off the lid before I started it to see what I could see. But yes, I'd seen some old looking stuff in one of the hoses when I changed them the other day.