JD425 Thermostat vs Water Pump ??

[sriddle1]

I own a '93 JD425 with Engine: FD620D K-Series. Starting to have issues with overheating with the temps in the low 80s here in NH. The engine is clean, checked air filter, radiator blown-out, radiator full with proper coolant, screen cleaned...? The engine is really getting hot (but the temp gauge reads normal) then the engine starts to skip and when I turn it off, I really have to let it sit a good hour before even attempting to re-start...... When I squeeze the lower radiator hose going to the Water Pump, no sound of liquid so.....perhaps the Thermostat or better yet Water Pump is the issue, maybe yes or maybe no..... :confused3:

Thinking it might be the Thermostat and :reading: reading other blogs, people write the old thermostat was rated for 160 degrees, now there's this chatter the gov't stepped in and made JD change it's design to run hotter at 180 degrees (anti-pollution). Apparently the hotter spec runs fine in later models but early ones (like my work horse) and carburation design not-so-good..... Then some out there who cite AutoZone has a 160 degree thermostat PN # 7203-160 that fits...and reading further, maybe I don't even need a thermostat at all since I store it during the winter after the last grass cut.

Comments welcome... THANK YOU !!

 

[Zebrafive]

My only experience with water pump failure was the seal (JD 285) so I would start with the thermostat.

 

[CobyRupert]

How do you know the engine is getting really hot, if the temperature gauge reads normal?

Can you run it without a thermostat to test if that is the problem?

 

[Clint S]

To issues running without t stat. Operating temp may not get hot enough to run efficiently, water will not sit in radiator long enough to cool as the stat offers some resistance to the rushing water. Theses are just maybe , it may run fine but a little cool without one.

 

[Kish318420]

Get a temp gun, and check engine, top hose, radiator, bottom hose, also run up to temp with radiator cap off to check for flow. That will help diagnose any temp problems.
Guns are available from auto supply shops now too.

 

[Zebrafive]

To issues running without t stat. Operating temp may not get hot enough to run efficiently, water will not sit in radiator long enough to cool as the stat offers some resistance to the rushing water. Theses are just maybe , it may run fine but a little cool without one.

I had heard the coolant would not be in the engine long enough to pick up the heat without a thermostat. Racers would experiment with hole sizes in a disc/washer in place of a thermostat.

 

[jsb2b]

Sounds like your thermostat is not opening....

 

[sriddle1]

How do you know the engine is getting really hot, if the temperature gauge reads normal?

The heat coming from the engine is really hot and as I said, it needs to sit before it will re-start and you're right the temp gauge still reads normal......

 

[sriddle1]

To issues running without t stat. Operating temp may not get hot enough to run efficiently, water will not sit in radiator long enough to cool as the stat offers some resistance to the rushing water. Theses are just maybe , it may run fine but a little cool without one.

Yes, read allot of postings recommending not to take it out because of efficiency.

 

[sriddle1]

Get a temp gun, and check engine, top hose, radiator, bottom hose, also run up to temp with radiator cap off to check for flow. That will help diagnose any temp problems.
Guns are available from auto supply shops now too.

"TEMP GUN"...…..That's a new one for me, I'll check to see if I can rent one, Good Advice, now the trick to find one...…..

 

[weathda]

Probably thermostat. Need a temp gun. Check your fan blade belt to make sure your fan is turning.

On edit: Harbor Freight has IR guns for about $25.

 

[sriddle1]

Sounds like your thermostat is not opening....

I thought the same but you never know, that's why I post on this site, there are those much smarter with mechanical issues that I could ever be. Last year a member helped me trace the wiring on my 790 that was affecting the shut off valve, saved me lots of money and I ordered the replacement module on-line and changed it out myself...… still though, I'm just a rank amateur in this area......

 

[sriddle1]

Probably thermostat. Need a temp gun. Check your fan blade belt to make sure your fan is turning.

Fan running OK, belt tight but I'll be checking on the "Temp Gun" aspect

 

[sriddle1]

Probably thermostat. Need a temp gun. Check your fan blade belt to make sure your fan is turning.

On edit: Harbor Freight has IR guns for about $25.

Thanks for the Picture, $25 pretty cheap, good to have one around just in case although my wife might say something different

 

[Zebrafive]

"TEMP GUN"...…..That's a new one for me, I'll check to see if I can rent one, Good Advice, now the trick to find one...…..

Harbor Freight puts out 20 & 25 percent off coupons all the time, makes the $25 temp gun $20

 

[Gittyup]

isn't the thermostat less than $25? It's a 25 year old tractor. Would be good to change it anyway. Has the CAM ever been changed in that tractor?