Petrol Dexta Compression

[DanielV]

Guys,

Now that the holidays are coming up I can fix my Dexta, it currently has very poor oil pressure when warm, cold its fine so I think the issue is the bearings tollerance at tempreture.
The problem I have is that I would like to do this on the cheap and quickly as it is summer and the grass can get to 7 foot in under a month, hence I am trying to decide how far to go.
Bareco have 3 rebuild kits an inframe an out of frame and an out of frame with crank, they also sell the individual parts.
I am seeing 80 to 90PSI on the 4 cylinders, what should a healthy motor be at?

If the compression is ok than I hope to start by pulling down all the equipment arround the motor to expose it check for leaks or other problems especialy arround the head if ok I was than going to support the front of the motor and remove the sump check the bearings front main and rods (I dont think i can get to the back main while still on the bell housing?) if the main was ok and crank looks good I was planning on just doing the conrods to get it up and working. If not I was thinking of just doing all the bearings with the motor removed, do you guys think that this would be ok or should I just rebuild it?

Can anyone tell me how heavy the block is with its internals, and clutch? I was hopeful that if I have to rebuild and remove the motor that i might be able to lighten it to just the block for removal without a super sized crane job.

Any advice or Ideas would help.

Thanks

[ol'Blue]

First of all I am going to start off by saying I have NEVER worked on a petrol Dexta.... But my experience with farm tractors and engines in general is fairly extensive.... Given the data you provided, I would pull the head and have the valves ground, pull the pistons and clean up the ring grooves, and install new proper sized rings, and of course, replace the bearing shells paying particular attention to the size stamp on the back of the shells. This will give you a in-frame rebuild good for many hours. If you have couple dollars left over, replace the oil pump while your in there..... This being said, if any of the bearing shells are wasted, or are showing a bunch of wear... you are in need of crank work.....

dave

[DanielV]

Thanks Dave,

Any one know the correct bearing tolerance? I have some plastgage but not sure on what I am looking for?

I have exposed the engine and decided to remove it, have help to do this tonight so I should have the crank and bearings exposed for inspection soon, hope the crank is good.

Now that I am pulling the motor I am thinking of doing a full rebuild, only concern I have other than the crank is the semi-finished liners, what do I have to do to finish? Is it just the cross hatch or do they come tight and I need to hone them to size?

Other than the 2 above points should I be looking for anything else or paying special attention to something?

Thanks for the help

[ol'Blue]

When the head is off, you can tell if the liner is worn or not by feeling the groove at the top of the liner where the piston rings end their up words travel. If you dont have much of a groove up on the top of the liners, then lightly hone it, wash it down good, and re-install the used, cleaned, pistons with new rings.... This is a compromised overhaul. It usually is good for many seasons.....but not as good as a full liner/piston replacement. Nor is it as expensive or labor intensive.

Dont forget to clean the ring grooves completely ... Any gunk left in the bottom of the ring grooves cause binding with the new rings.....

dave

[DanielV]

Thanks again Dave

Pulled the motor open and found the top of the liner has a big grove in the top and I can not feel any liner protrusion at all, when I turned the motor over to check the bottom I found that the con rod bearings have left heavy groves in the crank, explains the loss of oil pressure at temperature.

I think I will buy a full rebuild kit that comes with the crank.

Any one know what I should expect with plastigage with the new crank and bearings?

Any tips for doing a full rebuild?

I have read a few guides with the diesel motor but seen no information on the petrol

Thanks

[ol'Blue]

There is a link to an online service manual at the top of the dexta pages.... The crank clearances many be different between gas and diesel, but I doubt it. I am going to make an educated guess and say .002-.004 thousands of an inch. You can loose oil pressure on the cam bearings also....as well as a oil pump that is weak....dave

[DanielV]

I will check the oil pump and check that it is in spec but I doubt this is the probelm as I have good pressure cold so I know that it is moving the oil it may be going out of spec at tempreture but the damaged Bearings would cuase the pressure drop as the clearence expands from heat.
I hope that the crank bearings are good as I cannot find a list for replacement of them.

I have ordered a full rebuild kit with a new crank, I have also ordered new thrust bearing and spigot as the existing one felt gritty, I will have these parts tomorrow afternoon.

so far this has cost alot of money and I still need some more tools, so I would prefer not to have to buy anything more, any tips for checking the oil pump and camshaft bearings?

not too woried about the top end as it is easy to take the head off compared to the bottom end.

Thanks

[tom lad]

hi m8
prob not what u want to read but for me if uve bought the kit and spent on new crank , and every credit to u , then new main shell , big end ,poss little end ?, new oil pump would be my plan

do it once do it propperly.
if on rebuild the old oil pump fails after 2 hours then ull reck the engine and have to start again .

if the shells are worn u see the white metal rub down to the copper. also wear groves can appear .

only my opinion m8
good luck
tom

[DanielV]

Yea the rebuild kit was $800 and it comes with pistons, liner, rings, main bearings, con rod bearings, gudgeon bushes, crank, thrust washers, front and rear seals and top and bottom gaskets. I also ordered thrust bearing and spigot bearing for $50 as the existing feel a bit gritty.

So if I order an oil pump the only original part in the bottom of the motor will be the cam.

I plan on cleaning and lapping the valves for the moment and checking that they are still good as removing the head is no big deal but removing the motor is a pain, so I will probably just accept the advice and replace the oil pump.

If I find an issue with the cam shaft bearing liners, any one know a place that sell them?

As you guys are right only want to ever remove the motor once.

I will post some pics of what I have so far in a day or 2.

[tom lad]

good plan m8

as you say no big deal to sevice the head at a later date .

a m8 of mines oil pump failed on his big county , (1164 i think ) he'd re built the engine only months b 4 but didnt change the pump , the driver didn't notice the little light on the dash , some thing bit and it sezed solid on the high way towing a digger , a expensive re-build .
it was a tiny grubscrew that had sheared / snapped on the oil pump drive gear .

[DanielV]

My parts arrived today and I have striped the block except cam shaft, I cannot get the rocker caps from the cam out however I can slide the cam back and forward enough to see the surface of the bearings with a torch and mirror and they look good thankfully.

Only part I cannot remove is the liners, any tips? Tractor shop advised that the liners are not press fitted this agrees with the workshop manual however the old ones won't move. I was thinking of maybe some rhs bolted across the bottom and a bolt through this to some plate cut to fit over the liner and try to press out this way enough to get them started? Not keen on trying to hammer them out as I worry the cast might crack.

Also found that the top liner on the main bearings is probably worn and causing most of the problem as the top was no longer white but black worn out maybe?

I will take photos and post just been busy making sure that I check everything and have all the parts before everything closes for Christmas.

Any one have suggestions with regards to assembly fluids and items? Should I just use clean oil for assembly lube? Or is something like lock tight close fitting bearing lube worth using? Also the tractor shop advised that most of the new gaskets do not require any additional sealing or gasket fluid/goo, do you guys agree? For example in the book the rop seal needs to be dipped in gasket goo but the shop said that the new type do not need this and that I should not do it?

Any suggestions on assembly would help.

Thanks

[tom lad]

ive never seen a petrol dexta or worked on one
rope type seals soak in a jar of clean engine oil for a few days b4 use .

try as best as u can to keep everything spotless clean ,on re - assemberly . all bearing caps, pistons ect. lube with lots of clean oil , but gasket faces want to be clean + dry .
u want the inards to be lubed b4 u first crank up , so it isnt running dry / wearing .

unsure re. the use of gasket goo , with new gaskets , its a personal call i guess . i like blue hylomar , which is a non setting one .

only liners ive changed poped upwards / away from crank once the head was off.( the head holds them in place ) gentle tap with wood , some are pressed in by a special machine , i dont know which that engine has sorry . sounds like you'res will tap out tho dont it , prob a seal at the bottom of them to.

tractor and machinery + classic tractor mags both running features on engine re builds at the mo. uk magazines . prob of interest.
hope this helps

[Lesfen]

Hi,

Following your rebuild with interest as it may have to happen here shortly too.

I also think the liners would go up to be removed. (As Tom said)

A fellow Fordson enthusiast near here had trouble with the block castings being rusted and then cracking out between the cylinders after the liners came out on his Petrol Dexta.
He also was not able to source any new camshaft bearings after the machine shop mistakingly removed them when they cleaned the block and pressed in the new liners.
Cost him $500 to get new ones made up!

Cheers,
Les

[DanielV]

I am trying to push the liners away from the crank and out the top, they don't want to move, its a bit of a pain.

I do not want to crack the block so would trying to push them out be safer than trying to tap them?

Shame about your friends problem with the cam bearings as I was able to price a set from the local supply for 110, thankfully I do not think I need them.

Thanks for the advice

[Lesfen]

Only part I cannot remove is the liners, any tips? Tractor shop advised that the liners are not press fitted this agrees with the workshop manual however the old ones won't move. I was thinking of maybe some rhs bolted across the bottom and a bolt through this to some plate cut to fit over the liner and try to press out this way enough to get them started? Not keen on trying to hammer them out as I worry the cast might crack.

I vote for pressing rather than hammering.

Reread your post and now understand that you had the liners headed up and out.
Your homemade puller should work just fine.
but... what is rhs?

Les

[DanielV]

Its just square steel section, thinking of bolting this in the place of the crank shaft obviously I will pack it so the bearing locations are nor damaged than drill hole weld nut on underside run a bolt down to the liner and use a round plate to cover the bottom of the liner than screw in bolt and hope this breaks the seal and not the block.

Is it worth trying to run some WD40 or something designed to loosen rusted bolts down around the liners from the top?

Any one have any ideas on freeing the liners without damage to the block?

[ol'Blue]

I have heard of a trick used to remove liners that are stuck. I have never done this, so please search around a little, maybe there is a utube video on the subject. The trick I have heard is to use a arc welder and run a bead from the bottom to the top of the liner on the inside. This swells the liner, and then when it cools it will practically fall out. It may take a couple of beads one on each side.... The liners are pretty thin so if you do this take care.... Take a look at this topic and you will see what I am trying to get at...

http://www.tractorbynet.com/forums/part ... iners.html


Best wishs.....

[Lesfen]

Gotcha,
You are pushing it out!
Never thought of coming at it from that end.
Penetrating oil certainly can't harm.

Here's a link with a photo to a pulling method we have used several times.
Also gives support to the top of the block.

http://www.smokstak.com/forum/showthread.php?t=12598

Best of luck,
Les

PS>And would you know from where the local shop found the camshaft bushings?
Thanks

[DanielV]

Guys,

Not sure what photos you would like to see so I took some general ones showing the pulled down motor and the parts.

If you would like any particular photo let me know, I hope to get the sleves out tomorrow and begin cleaning everything.

Thanks

[DanielV]

Gentlemen, I give you success,



To the left is my home made puller worked very well, to anyone else doing this job on an old motor forget beating the liners out as it not going to happen without killing the block, corrosion is just too bad, thankfully the lip that the liner seals to is good so the new ones will go in nice.

Also found the likely cause to my high temps as the corrosion was soon bad that coolant would not likely make its way around the head or block, see next pic,



Tomorrow I start cleaning and making ready for the big assembly, any additional advice than what's above?

Not sure on how the local sourced the came bearings but the site for them is
http://www.northpinemotors.com.au/

Send them an email and ask, the guys are good at this place.

Thanks again to all the suggestions and feedback

[tom lad]

well done sir

give the inards a good clean ect.

what seals the bottom of the liner / the block , thats prob the bit i'd worry about .

plenty of corrosion isnt there , another reason to always run with anti freeze with anti corrsion properties rather that just water in the summer .

they came out of the head end then ?
all the best.
tom

[DanielV]

Yep they come out the head end, I always run coolant but the previous owner did not.

The seal at the block is fine no corrosion, its like the last 100mm of the block is a bore cut to just fit the liner with a figure 8 gasket. I may have killed the seal already tho as the tractor shop said that the new copper seal needs no gasket compound, so after fitting it I was preparing the crank and an instruction fell out the parts box saying that you need gasket compound so I took it apart and mangled the gasket, I have reshaped the gasket and used plenty of gasket goo, if it don't work I will just have to do it again, will only cost gaskets and fluid the second time around tho

The new crank is coated in black paint to protect and you need to clean it with enamal thinners which took forever, but the new crank is in and the main bearings are done and it moves nice.

Today I do the pistons seals and sump.

[DanielV]

The motor is back on the tractor and most of the bolt on items are done all I have left to add is the generator front wheel assembly and battery, tomorrow I find out if it works!

Any one know the procedure for running in a petrol dexta?

Will keep you up to date and take some photos.

[Lesfen]

Here's the link to the "running in" page>> http://www.fordsontractorpages.nl/manua ... a_om_4.jpg

Wish there was a link from the forum back over to the main http://www.fordsontractorpages.nl site!

And thanks for the connection to the dealer. I'll have to give them a shout!
Les

1 hour later>>>Ooops> Just noticed the home page link in the announcements area!!!

[DanielV]

I have it back together and it works!

Still testing and trying it out but looks good, I will take some photos.

Can anyone tell me the correct oil pressure that I should set the relief valve to?

Thanks