1995 Bobcat 743B Engine Knock

[CJames525]

After years of relatively reliable use, I noticed a knock after starting my engine. It starts probably 20 - 30 seconds after the engine has fired. This is a 1995 Bobcat 743B with the Kubota V1702 engine. Is this as bad as I think it probably is, or where should I go from here (besides trailering it to a shop)?

Video attached.

Thank you in advance.

 

[mrbb]

how many hours are on the motor?
knocks can come from a few different things
what OIL weight do you run in machine?
how old is oil in motor?

 

[CJames525]

Funny you mention that, as I literally just changed the engine oil this past week after it sat for the winter. Shell Rotella 15W-40 Diesel Oil. Since changing the oil, I probably put 15 hours on it. It has around 6,000 hours on the machine/engine.

 

[mrbb]

OK< well, with 6,000 hours on it, its getting to where things start to wear out, like bearings and such, which can cause a knock
Might want to look into what a rebuilt kit runs for your motor, and maybe have it rebuilt
that is if you feel its worth doing, as rest of machine will also have the 6000 hours on things, so your history on up keep and conditions on rest of machine need to be kept in mind!

and I am not saying that 6,000 is end of the world or ticking time bomb or anything, just saying, its not new anymore!

And we all need to be honest with how much $$ we are willing to put into machines, its rather easy to get caught up in repairs, only to spend more than the outcome will be worth in the end !
all the more so in today's world with every part costing so much more,(if even available on older machines)
plus if your not doing repairs yourself and paying someone to do the work, them labor costs can add up really fast to past what the machine is worth
over say than just maybe replacing whole machine !

and one last question for you, to maybe help ID knock,, does the knock go away if you raise RPM's
or does it stay the same?

 

[1702]

My 743b that is ready for a rebuild doesn't sound much different . Really hard to start this machine at this point gotta really ride the starter even on warm days. Trying to get through this one job with it before a rebuild / replace engine ill either rebuild my 1702 or get a 1902 or 2203 for it not sure which yet. I've had my machine a long time it's been a good machine certainly NOT new, but for how I use it these days (not very often) it makes more sense to fix it than spend big $$$ For a newer machine or buy someone else's junk. This machine doesn't owe me a dime at this point has paid for itself 20 times over. But before this job it sat for a long time and I made the mistake of loaning it to someone who clearly used ether on it even though I made it VERY clear not to ever use ether in it

 

[foton]

you could use a mechanics headset and probe around to find the loudest point the noise is, they are not pricey and it just might give you a clue what part of the engine the knock is coming from. but I would tend to fix it now vs. waiting and having it come apart and making it worse and more pricy to repair or making it a almost worthless core.

 

[laurencen]

one thing I know after rebuilding a few either is a killer on these engines, not hard to rebuild

 

[CJames525]

Thanks for the comments guys. I will check to see if the noise increases/changes with RPM's. I have never used either on it, but possible previous owner did years ago. It starts easy still, which is surprising it sounds.

Any idea what a rebuild on this may cost approximately? Are parts even available?

 

[Markle]

I replaced my 1702 with a remanufactured engine 4 years ago. I did the work. The engine was about $3500 then. Though parts are available, I didn't want to rebuild it myself …I've rebuilt many gas engines, but never a diesel, and if I remember the cylinders might have sleeves. Didn't want to futz with them.

 

[mrbb]

costs are going to vary pending where your located at and who's doing the work,
I know a dealer recently quoted my buddy to rebuild his new holland LX 885 motor at $13,500 to do it?
I know he plans to do the work himself and think he found a rebuild kit for about 2 grand! so he will be saving a lot of $$ doing work himself , as to paying someone.
also keep in mind if your not doing the work yourself, you will also have costs of hauling machine to and back from who ever is doing work,
so if you don't have truck/trailer to do so, this adds to costs
from what I seen by doing a quick search is a rebuild kit for your motor is about $ 1,000, to 1500.00+ pending where you buy it at!

Rebuild Kit for Kubota V1702 Engine - Indirect Injection

buy Rebuild Kit for Kubota V1702 Engine - Indirect Injection from HD Kits and Overhaul rebuild kit for indirect injected V1702 engine. Free shipping in the US, call 888-642-6460.

www.heavydutykits.com

Bobcat 743 & 1600 series Kubota V1702 engine premium rebuild overhaul kit - Rudy Diesel Parts

PREMIUM REBUILD OVERHAUL KIT FOR BOBCAT 743 & 1600 SERIES KUBOTA V1702 ENGINE ENGINE KIT COMPONENTS: 4 PISTONS WITH PINS & RETAINERS 4 PISTON PIN BUSHINGS 4 RING SETS 1

rudysdieselengineparts.com

every motor is different to get out and work on, , so this is just a ball park on a like job from a recent quote by a dealer in my friends area! above, is based on HIS machine/model, not your's

a private shop might be cheaper than dealer, but these days there pretty close, or some times higher, were in high costs for repair times anymore , since COVID happened, it seems everything has crazy costs to them, sadly!
but it show's you recent costs quote for a rebuild!

NOW as for a re manufactured motor seems to be about $6675.00 and UP for your machine too, if you went that way over a rebuild, , maybe a faster repair job, but will costs in labor to have removed/installed if your not doing the work yourself

Remanufactured Kubota V1702BR-GEN Engine | Country Sales and Service

Remanufactured Kubota V1702BR-GEN engine is rebuilt to spec to fit the Bobcat 743 Skid Loader. This engine is is in stock and ready to ship.

www.countrysalesandservice.com

Remanufactured Engine Assembly Complete Drop In fits Bobcat 743 1600 6562233 fits Kubota V1702 V1702B743

Engine Assembly, Complete Drop In for Bobcat Construction & Industrial(s) 1600, Skid Steer Loader(s) 743, Kubota Engine(s) V1702. Replaces Bobcat OEM nos 6562233, Replaces Kubota OEM nos V1702B743.

www.tractorpartsasap.com

So this is why I said, some times, the costs to repair can maybe be more than the finished product will be worth, pending on rest of condition of machine,
because as all machines get older, so do the rest of the parts on them, and things start to go bad one after another some times, the domino effect,
as in fix this, then next thing goes and so on and before long you sank a LOT of money into something, so IMO< you need to be honest in what your going to repair replace when machines get up there in either age or hours used,

and to be clear, I am NOT saying your machine will do this if you fix motor, , just adding food for thought on repairs that are higher costing! so you can weight repair costs as to replacing things, and only you know the condition of your machine and its use !

 

[CJames525]

Thanks for the feedback. I guess ultimately it will depend on the total cost if I go forward. There is a guy in my area that sells used V2203 for $2,500. Not sure if this is a good deal or not and if it is a direct replacement, but he states he has sold them to guys with the 743/743B as well.

I would prefer not to throw in the towel on the machine, as I dumped $2,000 in a new spool valve a few years back, new hoses, new glow plugs, new starter, new alternator, new solid tires, etc. I also wound up purchasing a 607 Backhoe attachment for it and have the machine setup with these brackets. Not sure what I would get for the machine for a bum engine and then sell of the model specific attachments, to then start over with a new machine and acquiring new model specific items.

If this is going to be real expensive, I may not have an option though and it may be the end of the road.

 

[mrbb]

yeah I hear you, its never a easy deal when big ticket items fail on things and you have to weight the costs to fix as to start over again, its a crappy situation to be in, been there and know it all too well!(just sank 9 k into a turbo on my truck just out of warranty and then had DEF emission crap failures adding another 3k, when it rains it pours sometimes, haha! )

funny or not funny maybe??
But if it was just 4-5 yrs ago, all these darn parts were about half what they cost now, its s shame the economy and inflation is so hard on every day people anymore, company's making record profits and government that doesn;'t seem to care about its citizens anymore!(sorry on the rant)

as for the V2203 engine being a direct fit
I have no clue, but would think someone here might know!

some extra food for thought
on sticking in a used motor,
before doing so I would make sure all was good, every test possible to be sure its solid!
and I would also investigate the costs to rebuild before installing , its way easier to rebuild when motor is out of machine, , so would be a lower costs deal, MAYBE!! and then you'd know your good for a long time with good basic care!

as nothing worse than sticking it in and short time later be back to having to r e do!
(had this happen with a transmission not so long ago, half price of new was the seller, then it failed a few weeks later, and ended up spending more then a new one would have the first time)

 

[Tazza]

You say the noise does not start straight away, there is a possibility it is an injector noise. With it idling, loosen one by one the injector lines to each injector, see if it stops when you disable one cylinder.

A v2203 is not a drop in swap, but it can be done easily enough. The rear main bearing carrier is larger, so you will need to modify your engine mount to make it fit the bolt pattern.

If your noise is indeed rod knock, get it machined sooner than later, we can do up to 1.5mm mm under sized conrod bearings for the 02 series engines. These cranks are not made anymore, so if you are going to work on it, do it before your crank gets beyond the grind limit.

We rebuild this model engine every week

 

[CJames525]

You say the noise does not start straight away, there is a possibility it is an injector noise. With it idling, loosen one by one the injector lines to each injector, see if it stops when you disable one cylinder.

A v2203 is not a drop in swap, but it can be done easily enough. The rear main bearing carrier is larger, so you will need to modify your engine mount to make it fit the bolt pattern.

If your noise is indeed rod knock, get it machined sooner than later, we can do up to 1.5mm mm under sized conrod bearings for the 02 series engines. These cranks are not made anymore, so if you are going to work on it, do it before your crank gets beyond the grind limit.

We rebuild this model engine every week

Thanks for the note back. I apologize, I may have misspoke, it fires instantly with no delay. Since I heard the knock, it's probably only ran for 1 minute total.

I am a bit out of my knowledge/expertise here, so apologize for the stupid questions. I live in Connecticut and will need to find a machine shop to shorten the rods by 1.5MM (assuming it is rod knock)? It is hard to find people to work/know anything about these older machines.

 

[UnexpectedBill]

Thanks for the note back. I apologize, I may have misspoke, it fires instantly with no delay. Since I heard the knock, it's probably only ran for 1 minute total.

I am a bit out of my knowledge/expertise here, so apologize for the stupid questions. I live in Connecticut and will need to find a machine shop to shorten the rods by 1.5MM (assuming it is rod knock)? It is hard to find people to work/know anything about these older machines.

I've been watching this thread, and as an old gas engine mechanic I can't help but wonder... What do you deisel guys think about this?
1st, Since it does start and run well, check & eliminate the possibility you have a valve that's out of adjustment. Valve lash gets looser as the engine warms up, it seems weird that it doesn't knock at startup, and I have - very rarely - seen an adjustment come loose.
2nd, if it is the bottom end, the biggest thing is to stop using it before rolling a bearing scoring the crank beyond hope. Pull the engine, drop the oil pan, and inspect the bearings ad journals. With 6k hours they will be worn. More importantly, how does the crankshaft look? If it looks okay, measure it with a micrometer to verify the size, that it hasn't been machined before.
If still good, roll in a new set of main & rod bearings and reassemble with new gaskets.
Is this the best route? Obviously not. But if the engine is in otherwise good shape, it's an economical way to squeeze a few more years out of it while you save for the inevitable rebuild / replacement. I've seen this done.

 

[UnexpectedBill]

Thanks for the note back. I apologize, I may have misspoke, it fires instantly with no delay. Since I heard the knock, it's probably only ran for 1 minute total.

I am a bit out of my knowledge/expertise here, so apologize for the stupid questions. I live in Connecticut and will need to find a machine shop to shorten the rods by 1.5MM (assuming it is rod knock)? It is hard to find people to work/know anything about these older machines.

BTW- I have an old NH L555 with a kubota 1902 in it so I am interested. I also have seen this done successfully on many old gas motors, so I'm looking to here from you experienced deisel guys.

 

[CJames525]

So after letting it sit for 2 days, first is cold start.
Second video, I turned it back on after shutting of off right away at end of first video to try raising and lowering RPM's to see what it did, then it stopped making sound. I ran it for a minute and nothing. Does this change things at all?

Thank you all again for the help.

 

[mrbb]

Thanks for the note back. I apologize, I may have misspoke, it fires instantly with no delay. Since I heard the knock, it's probably only ran for 1 minute total.

I am a bit out of my knowledge/expertise here, so apologize for the stupid questions. I live in Connecticut and will need to find a machine shop to shorten the rods by 1.5MM (assuming it is rod knock)? It is hard to find people to work/know anything about these older machines.

a good way to find a mechanic in your area, might be to try contacting the local equipment rental shops in your area, most of them either use a mobile repair guy, or know of one
that might be able to come to your site and give you an evaluation what they think is wrong

Knocks, don't tend to fix themselves, unless was bad fuel or a stuck valve or likes
but with again the hrs on your machine, anything can be possible, I would be keeping a close on/ear on things

 

[UnexpectedBill]

So after letting it sit for 2 days, first is cold start.
Second video, I turned it back on after shutting of off right away at end of first video to try raising and lowering RPM's to see what it did, then it stopped making sound. I ran it for a minute and nothing. Does this change things at all?

Thank you all again for the help.

Just listened to your videos and IMO that does not sound like an internal engine knock. It sounds to me like something external is loose and rattling due to normal engine vibration, like an exhaust clamp, or maybe something fell between a belt pulleys and cover. I don't know what it is, but I'd start looking all around the engine bay for loose parts.
Hopefully someone on here knows these machines and will recognize that rattle.

 

[CJames525]

The most recent videos do sound that way, as if it's something loose externally. It definitely sounds different than the first video/how it did the other day. I'm going to mess around with it tomorrow evening and see what I can record/reproduce.