First time user of this site and hoping to get some help on a 425 I just purchased. I bought this mower from a John Deere dealership that I had to make a 14 hr round trip to get. They had it listed for $1800 and it was a 2000, so that is why I drove so far to get it. I figured part of the reason it was so cheap was that they said they never serviced it. I don't know if this is common practice, but I'm starting to think not. I was promised it ran, drove and mowed good, which it did. I had noticed an oil leak out of the front main seal which was no big deal beings it could easily be replaced by removing the battery, prying out the old one and putting in the new one. I got it home and replaced the front main seal and also replaced the o-ring on the bottom of the dip stick beings I noticed someone had caulked it and it was leaking, also did all the other maintenance on it, which included changing oil, oil filter, air filter, trans fluid, trans filter and fuel filter. I didn't change the plugs because they looked brand new. Upon further inspection after driving and mowing with it for 10 min at home, I noticed the top radiator hose was loose and leaking, so I tightened that up. I am thinking the mower is still using coolant cause it keeps dropping little by little every time I use it and when I drained the oil when changing it, it looked like it had a green tint to it and it seemed like there was water in it. So my question is... what is my first step to figure out where the coolant is leaking? There are no leaks externally. Also I noticed that the temp gauge will rise up to 3/4 on the gauge and then drop back down to 1/4. It does this continuously. Is this normal? Sorry for the long story... and thanks for the comments!
"K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts" 7 down engine shop manual, new head gaskets, heads need to be reworked at machine shop or by yourself, new thermostat, check hoses & belts for replacement, flush radiator and pressure test, check water pump for replacement as well as belts & radiator cap, change oil & filter last.
Yes to first two questions, no to stopping fuel, follow directions in manual starting at 4.6. Let us know how it goes, thanks.
#3
DevonD
thanks mechanic mark. So would a compression check of the cylinders be ok to do first? Would that tell me if the head gaskets or heads were bad? I have a compression tester? Should I stop the fuel pump from injecting gas into the cylinders when doing this and how would I go about doing that? I read that the cylinders should have a minimum of 180lbs of pressure in the manual. How long should it hold this pressure?
#4
NorthBama
An air leak down test will tell if a gasket is leaking.
#5
DevonD
OK...had a chance to do the compression test on the mower today. The thermostat side had 175psi and would hold it for 8-10 min and the other side had in-between 180-185psi and would also hold pressure for 8-10 min. I never tried any longer, I figured this was long enough wait. The plug on the thermostat side was black and had carbon on it and this was the cylinder at 175psi. The other side the plug looked like a new plug. I ran the mower for another hour in the past two days and couldn't get the coolant level to drop anymore. It has been on the low fill line since then. So... maybe it took the first couple times of running it for the block/heads to fill back up with coolant after I tightened the hose up that was leaking. Now back to the manual I guess to see what I do next unless someone has some advice on what to do next?
Also I was wondering if these motors have a ticking noise to them? Cant tell if its both sides or one. I use to have a 345 with the 18HP liquid cooled Kawasaki OHV and I thought it purred and never made a ticking noise.
stick it on your trailer and take it to your local car mechanic / radiator repair shop[.
Get them to do a pressure test on the radiator.
If it is leaking externally you will see the little stream of water and if it is leaking internally you will see a pressure drop.
I am guessing there is no overflow tank so it might be the drop in the water level is caused by thermal expansion.
The temperature variations could be due to blockages, thermostat or water pump
#7
DevonD
Yes there is an overflow tank for the coolant. That is how I noticed that the coolant was dropping, but has stopped dropping since I fixed a hose. It just took longer than expected to fill the system back up with coolant after I repaired the leak on the hose. I don't think it needs a coolant psi check anymore beings its not using anymore coolant. I do agree that is prob needs a thermostat beings the temperature gauge fluctuates so much. The thing I am wondering about now is why one cylinder, the plug looks brand new and the other cylinder the plug is all black and full of carbon? I did look at the manual again and I guess the minimum cylinder pressure is 170psi and cant be more than 14psi difference from one cylinder to the next. So the engine does fall into normal operating specs. Would this mean bad valves or the valves need adjusted on the one cylinder? Don't understand why on one side everything is good and the other side looks like crap?
Both of those plugs are bad.
The clean one is lean, not clean and the other is rich.
So you have problems .
I will go with a cracked head at worst or a blown gasket at best.
Pull the rocker covers and watch the operation of the valves.
While you are in there check the valve lash.
Both sets of valves should look & move identically.
When the valves are fully closed rotate the pushrods and look for eccentric movement indicating a bent pushrod and most likely a sticky valve..
Not uncommon for a carburetor to be adjusted to counteract a problem further down the line.
We have all done it
#9
DevonD
Ill try and get at that within the next couple of days and let you know what I come up with. Thanks for the input!
#10
DevonD
Ok I finished up mowing what I had to before tearing into the mower. The only thing I have done so far is took the plug back out on cylinder 2 I believe (thermostat side) and I noticed the prong on the spark plug is bent in towards the center piece of the plug and there is only .005 gap on the plug and it looks like an indent on the piston where it was hitting the plug. Not sure how this happens? I will keep updating once I check the other side and get the valve covers off and check out the rods on both sides. You can see how the prong is bent on the plug. There is also a flat spot on the plug from the piston hitting it.
UPDATE: Cylinder 1 (non thermostat side) pulled plug, looks like very slight contact with piston, slightly bent .019 gap. Valves lashes were way off on a couple.
Cylinder 2 with smashed dirty plug had Exhaust .016 Intake .025
Cylinder 1 with lean plug Exhaust .025 Intake .008
According to the manual they should all be set at .025. Would this cause the pistons hitting the plug(s)? Will check the rods next I guess by pulling them out. Do I pull the heads and see if the valves are bent or should I just adjust the valve lash and call it good?
I looked up the NGK BPR4ES factory spark plug gap and they are suppose to be at .030.
First check they are the right plugs.
On a mower engine the piston should never get any where near the plug so I an guessing some one put in the wrong plugs.
Those are "Projecting Electrode" type plugs.
SO my very first thing would be to swap them for BR4ES, the P is for the longer center electrode.
The piston hitting it will do damage to the piston , rod & even the crank.
Do not use the engine in that condition.
Stick some thing down the plug hole and put a bit of weight on the piston, then rotate the engine. If you feel a "click" any where, the rod is loose or bent.
#13
DevonD
I stuck a 3/8 drive extension in the hole and turned the flywheel while pushing on the piston and never heard or felt anything. I have know idea what model I have beings there is no serial # on front of engine. So many revisions...
I will give the BMR4A a try. Hopefully they are shorter. It looks like that is really the only other one listed for this motor. I just remembered too when taking cylinder 2 plug out that the threads were slightly striped...that must be because the piston kept hitting the plug. Do you think I should tear down and check the whole engine or do you think I'm safe running it and trying out the shorter plugs. What would you do if it was yours? Like I said I didn't here any noise or feel any clunking and I did adjust the valves to factory spec now. Oh and do you think I still have a bad head or head gasket beings the valve adjustment was way out of wack or wouldn't that still make that one plug look like crap?
For now I would go with the shorter plug.
If it gives you grief, do not force the plug in but get a plug thread tool , put some axel grease on it & run it down the plug hole.
Remove the tool clean up around the plug hole. fill the cylinder with light oil and crank the engine with no plug.
This will eject any swarf that may have dropped in to to pot.
As for plug thread length, the plug should not have any threads inside the head so you can measure the depth of the plug hole and then compare that to the length of the plug
#16
DevonD
Went to the John Deere dealer today and got the BMR4A NGK plugs and what a difference in size. The BPR4ES NGK is twice as long. If this shorter plugs are the right ones I cant believe that those other plugs didn't do anymore damage than what I can see. That doesn't say that the inside of the engine is ok I guess, but I hope I caught it in time. The parts guy at John Deere said that the Kawasaki FD620D has 2 different style of heads on them and when people go to buy the maintenance kit for those motors they just grab one beings everything is the same in the kit and not knowing they sell 2 different kits with different spark plug sizes. I also picked up new push rods for the engine too beings they were only a couple dollars a piece. Don't know if they were needed but figured I might as well. I would like to just take the heads off and make sure the valves are good and clean beings the lash was off so much on them, but don't want to tear into anything and spend extra money if not needed. Thanks for the tips on re-threading of the spark plug hole and what to do. Appreciate all the help. Will let you know how I come out on everything here in a couple days.
You can see how the prong is bent on the plug. There is also a flat spot on the plug from the piston hitting it.