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Engine rebuild

Posted: Wed Jan 02, 2019 11:30 pm
by Patrick98
Hello . Just wondering. I have a 996 and was thinking of doing engine up as there is starting issues and is linked to valves wear and fuel pump wear and possibly compression.. I have little experience of mechanical work but I have a good idea of what to do.. I changed the water pump in her and the whole set up looks quite simple . Basically I'm asking, if I'm on my own with virtually no mechanical experience and all the time in the world could it be done if I had everything at my disposal and if so, how long would it take an amateur like myself to do it.. I was planning on getting engine sent to get a reboar. I'll abviously put new pistons heads in and so on... with valves, injectors and pump referbished.. What do you think?? Is there any advantage money wise??
Thanks.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 2:04 am
by GeoffDEAL
Hi do the starting issues relate to engine condition,does it run good when started ie- oil use-- motor fuming --hard starting can be lack of fuel --fuel pump or kit, is it hard starting in hot or cold conditions --with excess fuel start on ect . These motors have to be really bad and worn out before they wont start, have a 1494 has done well over 12000 hours uses heaps of oil fumes away But always starts except in coldest conditions. If you are really concerned about motor condition the head off will confirm and new exhaust valves are a good idea as heads have a habit of breaking off and wear mark on cylinder can be checked for condition. If you need to go further get a good workshop manual and go carefully and you will get there but check and get advice on what is necessary first.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 5:41 am
by ollek
Geoff, the problem with wearing and breakage of exhaust valve stems only relates to older engines with cups between the valve stem and the rocker lever.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 6:28 am
by GeoffDEAL
Hi ollek my two were 1200 and 1494 no cups just bad valves the heads broke off them, have heard of others, replacement valves of any make never failed, its a good idea to replace the exhaust valves on any head job why risk it they are not expensive. cheers Geoff

Re: Engine rebuild

Posted: Thu Jan 03, 2019 7:40 am
by philedge
@patrick. You had a previous post on poor starting and there was never any conclusive findings but vague suggestions from your trusted mechanic about a variety of possible causes. Did you ever do a compression test To check engine condition? Ive just had a quick look at the original thread and your engine runs "100%" once started- correct??

Id suggest you do a little bit more diagnosis before stripping the engine for a rebuild. Even doing the work yourself youll be spending £100's on a rebuild in materials alone.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 8:25 am
by philedge
Forgot to say that if you do want to strip the engine but arent to confident, you could get an old car engine from a scrap yard and strip that to get a feel for whats inside an engine. Youll probably struggle to find one, but an old push rod engine would be ideal.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 2:29 pm
by Gard
I think there are a list of things you should carefully look at before and as the engine is being disassembled to try to see what problems are there. Here are a few ideas, I am sure there are others more knowledgeable than me that can add to it.
Already mentioned, compression test, make note of RPM, engine temperature and retest after adding some oil to each cylinder
Leak down test of cylinder
Crank case pressure of running engine
Measure valve gaps before removing head
Inspect head and cylinder for signs of head gasket sealing before clean up
look for oil leaks, plan on replacing all seals you can get access to
Get the official David Brown service manual that has engine rebuilding details and specs
Other engine rebuilding books?
Lots of photos and notes along the way,
Organize small parts in labeled boxes or bags as they come off.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 2:46 pm
by Patrick98
Hello everyone.. thanks for all ur views on the subject.. there is a small amount of blowback from the dipstick tube.. enough of a blow that u can feel.. starting her in the cold is the same as starting when it's warm.. the cold start makes very little difference to her.. I was just wondering about the engine rebuild because I would be interested in doing it.. the idea of getting an old engine from a scrap yard is a good idea.. I can't getting testing her as I'm busy at the moment but I'll will get at her.. as I said I replaced the water pump and it was a simple enough task.. so looking how long the process will take and how much would it cost if I were to do it all myself.thanks again

Re: Engine rebuild

Posted: Thu Jan 03, 2019 5:12 pm
by Wheelie
Well from the experience of reconditioning a 1490 engine,fistly it's well worth doing it and I would say do it from top to bottom leave nothing out and even get the block skimmed too,all may seem like a daunting task but once you have the time to do it then it will be well worth it,but don't underestimate the cost because that can run wild with things like crankshaft rework, engine oil pump problems etc which will only be noticed when everything is taken asunder,even dodgy radiators!all I would say is expect the unexpected!and may stick in a new clutch as well!

Re: Engine rebuild

Posted: Thu Jan 03, 2019 5:59 pm
by philedge
Old tractor engines are relatively simple compared to modern engines so if you work methodically you should be able to strip and rebuild an engine with the aid of a manual and this forum. A bit of practice on an old 4 stroke engine will help with confidence and understanding of how bits fit together and interract with each other.

Its likely that it may be some time from when you start the strip down to when you finish, so you are likely to forget how things were before strip down. So that you can get things right keep a photo record as you go along so youve got decent pictures of each area as it looks now AND as its gets stripped. Store the parts methodically and get a metal marker to mark things in the position they were when you stripped them off- direction/cylinder number of pistons, con rods, big end caps etc. Anything that has nuts and washers holding it in place should be stored with the right nuts and washers fastened to it with tape or cable ties- dont put all the fastners in a bucket or you'll never get the right fixings in the right place!!

Camshaft and injector pump have to be installed in the correct position relative to crankshsaft position so be clear how these things will go back together before removing the injection pump, camshaft or their drive train. Timing of these will be covered in service manuals but its much easier if youve seen the correct positions and timing marks BEFORE you dismantle them.

When you get the time its still worth finishing off the diagnostics to get a clearer idea of whats wrong before you head off pulling things apart.

Re: Engine rebuild

Posted: Thu Jan 03, 2019 8:10 pm
by rid54
"Blowback" from the engine sump is not any kind of indicator unless really measured in some way. There is always a sort of "pumping" going on, with the pistons moving and causing pressure gradients to be felt in any opening into the crankcase. Normally, there are two openings; one at the top (working through the pushrod holes into the valve cover and out through the breather), and the dipstick hole and/or a breather tube from the crankcase itself. If pressure builds, there is of course a problem, but the problem may be with crankcase ventilation rather than piston rings... A certain amount of gasses escaping into the crankcase is normal. These gasses should be vented out into the free through whatever openings may exist. If the pressure blows out the dipstick, there is a problem, of course, but the problem may be in the venting system rather than in the cylinders. The whole picture must be considered.

Re: Engine rebuild

Posted: Sun Jan 06, 2019 12:32 am
by bedwards1966
Your breathing from the crankcase does not sound to be excessive so isn't a reason to rebuild.

Tell me more about the starting problems.
If the compression is suspected to be low I suggest doing a compression test before pulling anything apart - you don't want to strip the whole engine to find that there wasn't anything wrong, or that it was nothing more than just valves.
Has it got good oil pressure - in which case I'd be wanting to leave the bottom end alone.
Does it use an excessive amount of oil?

Engine rebuilds are not difficult, but it is time consuming and requires patience and care to get everything clean and put together correctly.
It can also get very expensive. Sometimes an engine is pulled apart for one thing but then other things are found which need correcting and it can start adding up. For instance, pull out the pistons and end up getting it bored and new pistons. Look at the crankshaft and find it needs grinding. Get the injectors checked and find they need money. Decide to get the injector pump checked over while you're at it, take a look at the camshaft and find it's badly worn - sometimes it can be a can of worms that ends up costing a fortune, other times it's just a simple fix. I never suggest pulling an engine apart without good reason.

Re: Engine rebuild

Posted: Sun Jan 06, 2019 4:37 pm
by Patrick98
bedwards1966 wrote:
Sun Jan 06, 2019 12:32 am
Your breathing from the crankcase does not sound to be excessive so isn't a reason to rebuild.

Tell me more about the starting problems.
If the compression is suspected to be low I suggest doing a compression test before pulling anything apart - you don't want to strip the whole engine to find that there wasn't anything wrong, or that it was nothing more than just valves.
Has it got good oil pressure - in which case I'd be wanting to leave the bottom end alone.
Does it use an excessive amount of oil?

Engine rebuilds are not difficult, but it is time consuming and requires patience and care to get everything clean and put together correctly.
It can also get very expensive. Sometimes an engine is pulled apart for one thing but then other things are found which need correcting and it can start adding up. For instance, pull out the pistons and end up getting it bored and new pistons. Look at the crankshaft and find it needs grinding. Get the injectors checked and find they need money. Decide to get the injector pump checked over while you're at it, take a look at the camshaft and find it's badly worn - sometimes it can be a can of worms that ends up costing a fortune, other times it's just a simple fix. I never suggest pulling an engine apart without good reason.

She isnt burrnung Hugh amount of oil if any.. she's very smoky when starting with preheat on cold day. the fuel pump is leaking slowly which I think is worn and the air intake is very dirty and needs attention.. will get pump looked at and clean up the air filter. Compression test is also on the list after the pump..

Re: Engine rebuild

Posted: Sun Jan 06, 2019 5:26 pm
by ollek
You wrote. "the air intake is very dirty ". Cleaning the air filter and the inlet channel is a normal service that has to be done with in the operators manual mentioned intervals. You MUST do all periodic services mentioned in the Operators Manual correctly as stated in the manual, or you will end up with lots of different problems. You also wrote:" the fuel pump is leaking". Dou you mean lift pump or injection pump? A leak at the lift pump can be fixed by changing the diaphragm and cleaning the inlet and outlet valves in the lift pump. Start Do a proper and full periodic service to your tractor as I have a feeling theta this has been neglected for a long time. Also please, check the valve clearance at the same time and adjust if needed. There is no point in trying to find any fault if the basics are not taken care of.

Re: Engine rebuild

Posted: Sun Jan 06, 2019 6:16 pm
by philedge
Theres already at least 3 other topics on what appears to be this same tractor, one titled blow back, one titled fuel injectors and one titled 996 starting problems. Might be worth resurrecting the "996 starting problem" topic as this one is starting to cover exactly what has already been said!!