Proper forum suggestion for my JD400 backhoe

[oldmetalmender]

Along with my 450C crawler, I have a 69 JD400 backhoe. Do any of you guys have a suggestion for a good forum or a site for talking about that machine? It has wheels. No plans for tracks just yet.

[Stan Disbrow]

Hi,

We usually discuss wheel tractors right here. Off topic for crawlers, but most of us have ones which are related to the crawlers.

Stan

[oldmetalmender]

Sounds great Stan. I didn't want to talk apples on an orange forum.

My JD400 has a pinhole in the diesel block. It appears to be a casting flaw. I have looked on the JD parts finder site and near as I can tell the diesel block is the same as the gas block. Sometimes the parts finder site has so many superseded part numbers it's confusing. Near as I can tell it is the same. I was going to degrease the hole, give it a light grind or sand and try JB weld to seal it. That would be my first attempt to repair it. It's weeping oil and getting messy. I know it needs engine work (bad valves) but it runs and starts really well. I have dumped an absolute pile of money in this machine. I was lucky to purchase it really cheap. It is really coming around and is a definite keeper. Just wondering about the block being the same as a gas motor.

[jtrichard]

Watch this and read the comments https://www.youtube.com/watch?v=vgnQmfiIo9k You could also pin it or use 310-16 rod and weld it (a little at a time)

[oldmetalmender]

Looks like JB weld it is. It is a very tiny casting flaw. A hole smaller than the diameter of a pencil lead. I watched the video and the follow up video. Glad to hear it worked for that guy. His crack in the block was huge.
I am still wondering if it is common to have the same block for gas and diesel. I know the heads will differ. I meant to take a picture of the leak today. Got busy finishing a Military trailer repair and had company for dinner. I forgot to snap a photo. The day flew by.

[jtrichard]

I would say gas vs diesel are NOT the same JD shows 5 different #s for gas and NO # and NO longer available for diesel

[oldmetalmender]

I would say gas vs diesel are NOT the same JD shows 5 different #s for gas and NO # and NO longer available for diesel

That's what I thought. Fortunately the hole is super small and most likely able to be plugged with JB weld. I have searched some of the dismantling yards back east. I only see the JD400's once in a while. Now to wait for spring and all this snow to melt off.

Thanks for the reply.

[jtrichard]

JB should work if not then if there is not a Webb behind the leak you could drill it and tap it to 1/8"1/4".3/8" or 1/2" pipe and that would fix it also ..... NO one gives those blocks away so you could spend a fair amount of time fixing it and as you said it is very small

[Lavoy]

The other thought that just struck me is go to a machine shop that does head repair and see if they have any of the tapered pins that are used to repair head cracks. The go down pretty small, you might need to only clean the hole up to the correct size, screw the pin in, break it off, and peen the remains flat.
Lavoy

[oldmetalmender]

That is most likely a better repair than JB weld. I have to take some older buick 350 exhaust manifolds in to a machine shop in a couple days. I'll ask about that. I am concerned about making it bigger as I can't tell how bad the flaw is on the inside is if it is a flaw. I need to get a picture of it up here.
It has gotten messy with the thinner oil I put in for cold weather. I need to pull the pan and have a look. In my spare time. My spring and summer are filling up fast.

[oldmetalmender]

Well shoot... Almost a productive day. I think the peened pin might have to wait for later. I have no idea how much block material is under the pinhole. Also I have been wanting to install my coolant heater to go with the oil pan heater I put on a while ago. So changing my coolant back to regular ethylene glycol based coolant today seemed like a good time to do all this. I'm hoping I won't need to replace the block later.

Here is the hole. And a lot more oil since I put thinner stuff in for cold weather. Draining the coolant also.



Cleaned up revealed two holes although only one seems to be weeping. That moisture is brake clean.



A little smear of JB weld.



And how it sits right now. It's pretty cool here so the light will help set it up. I tapped into the block in the same places as the JD parts finder site, and the manuals.

Now that spring is around the corner.... Better late than never. Both my wife and I still think we will get a cold snap. And I am getting lazy. I didn't paint the mounting bracket.



That should hold it for now.

[Lavoy]

Tank heater will work a lot better if you plumb the top hose into a tee at the temp sending unit.
Lavoy

[oldmetalmender]

Tank heater will work a lot better if you plumb the top hose into a tee at the temp sending unit.
Lavoy

Up at the elbow that goes into the cylinder head is a large allen socket pipe plug. I wanted to hook up there. The ports would be almost the length of the engine apart. But I just could not get it loose. I put an allen wrench in it and even got a jack handle as a cheater bar. No go after several tries. I was expecting the wrench to shatter or the socket to strip out. Then started wondering about doing it my way instead of what's in the manuals etc. Common sense says to do what you are saying as the hook up like I just did from the JD site seems like it would only heat the middle cylinders. . I don't have all the coolant back in yet. And I just returned from town with NAPA kool for both machines. I was just going out to finish it up as a huge pile of snow and ice fell off the roof 20 feet long right where our path is to the front door is. I need to move it. Thanks for mentioning this. I'll try to spread these fittings apart more.

[Lavoy]

I have never tried to get that damn plug out, just always used a tee at the temp sender. It pretty much always come out easily.
What you did will work, probably less efficient. The one problem I do see is if it can't circulate enough cool water, it may tend to temp out and not run as much.
Lavoy

[oldmetalmender]

Well I got it. But not without making me work for it. That plug has been in the cast elbow for 47 years and did not want to come out. I used a 18 inch 1/2 inch drive breaker bar with a reducer to 3/8 drive hooked to a socket driven 3/8 allen. Right when I felt it start to turn it broke the allen.
Luckily for me I had a 1/4 drive socket with the same 3/8 allen pressed in. I pressed it out and using a bearing press installed it back in the socket I just broke. It worked... Carefully applying torque it slowly twisted out.
This is what I wanted to do from the start. On both machines. The thermo siphon will function better this way. And thanks Lavoy for giving me the nudge to go after this fitting again. It was a bear to remove. I forgot to mention that the water pump bypass elbow up at the thermostat is indeed below the thermostat but to short to tap into.
The 450C cast elbow is untapped. Drilling and tapping will be easier I am sure.

A pic of it... The hose is inches away from the injection pump throttle rod. It looks close but it is not.



And a bonus pic. Now I can use my forks I just built. But it's really hard to move snow with these.




Cheers!