Author Topic: !979 Rabbit Diesel Need help!  (Read 42758 times)

Reply #60July 05, 2012, 01:19:42 pm

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #60 on: July 05, 2012, 01:19:42 pm »
okay so ive pulled of the head and have noticed some junk in a few of the head bolt holes so gonna try and clean those all up is there any like tap i could get to just really clean the threads what do you guys suggest doing? i sprayed some wd40 cuz i ran out of carb cleaner ha in each hole and gonna vaccum it all back out maybe they should clean them up nicely bit i just want to make the threads perfect again so i can get the head torqued down perfect hopefully that will fix my compression :)




Reply #61July 05, 2012, 03:42:11 pm

745 turbogreasel

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Re: !979 Rabbit Diesel Need help!
« Reply #61 on: July 05, 2012, 03:42:11 pm »
I filed flutes in an old head bolt to make it into a cleaning tap.

Reply #62July 05, 2012, 03:52:37 pm

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #62 on: July 05, 2012, 03:52:37 pm »
I filed flutes in an old head bolt to make it into a cleaning tap.

okay maybe ill try that!


Reply #63July 06, 2012, 02:08:21 am

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #63 on: July 06, 2012, 02:08:21 am »
okay so go the head back on torqued all down did compression test still the same numbers... so i guess now its time to pull the engine and just replace the rings? or could it be my valves are not in time? could that be cause of low compression?

Reply #64July 06, 2012, 03:25:04 am

nathantheengineer

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Re: !979 Rabbit Diesel Need help!
« Reply #64 on: July 06, 2012, 03:25:04 am »
i am just thinking out loud here,  have you thought about doing a leakdown test?  if you havent got the gear then someone local will have.

Basically compressed air is injected into each cylinder (making sure that the two valves ar 'on the rock' i.e. closed and the cam isnt acting on them) and then you measure the amount of time that the engine hold pressure. 

If it drops slowly then rings are working, maybe not perfectly but working nonetheless.

If it drops rapidly then something is not right, either rings, valves not seating properly or a crack in head/block.

To check if its valves then all you have to do is make sure the air is leaking out the inlet or exhaust manifolds.  If it is, valves/ head issue if not then bottom end issues.

As you have put it back together i would do the leakdown next to see whether head needs remedial work or if the rings need doing.


Might save a bit of time and at least helps to pinpoint the area of engine that needs investigation.

Kind regards

Nathan

Reply #65July 06, 2012, 03:26:14 am

745 turbogreasel

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Re: !979 Rabbit Diesel Need help!
« Reply #65 on: July 06, 2012, 03:26:14 am »
okay well heres the deal i bought the car for $500 the engine that was in it the block had a broken rod the go threw in 2 other spare 1.5L diesels one complete and the other was just a tranny and block so what i did was i took the head that was on the car orignially got all the valves and everything re done on that
Got exactly what redone?
Was it pressure tested?
check it for warpage  just in case
Was valve clearance checked? make sure there is some clearance with the cam lobes pointed up.
check the one from the donor block for a big warp at the middle, or a crack  to H2o.
Never presume that because a machine shop  did work that it was done right.


and i took of the blocks that i cranked and it was free from binds and what not and i didnt do anything to the block except put on a new clutch kit and oil pan i

... i probably should of thought this wasnt right and stopped but i kept going and i torqued them all to 36 or whatever the book says.. do you think maybe because they were hanging up they might of been torqued but it was not accurate reason for not having the compression?

clean it well, and measure stickup of all 4 pistons very carefully.  if this block previously hydro locked  in these 2 adjacent holes, the rods may be quite bent.  all 4 should spec  for the same head gasket thickness at the least.

What is the procedure you are currently using to tighten the head bolts?

IMO ring wear in 2 cyls is not the most likely  thing.
« Last Edit: July 06, 2012, 03:29:05 am by 745 turbogreasel »

Reply #66July 06, 2012, 02:21:11 pm

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #66 on: July 06, 2012, 02:21:11 pm »
okay well heres the deal i bought the car for $500 the engine that was in it the block had a broken rod the go threw in 2 other spare 1.5L diesels one complete and the other was just a tranny and block so what i did was i took the head that was on the car orignially got all the valves and everything re done on that
Got exactly what redone?
Was it pressure tested?
check it for warpage  just in case
Was valve clearance checked? make sure there is some clearance with the cam lobes pointed up.
check the one from the donor block for a big warp at the middle, or a crack  to H2o.
Never presume that because a machine shop  did work that it was done right.

and i took of the blocks that i cranked and it was free from binds and what not and i didnt do anything to the block except put on a new clutch kit and oil pan i

... i probably should of thought this wasnt right and stopped but i kept going and i torqued them all to 36 or whatever the book says.. do you think maybe because they were hanging up they might of been torqued but it was not accurate reason for not having the compression?

clean it well, and measure stickup of all 4 pistons very carefully.  if this block previously hydro locked  in these 2 adjacent holes, the rods may be quite bent.  all 4 should spec  for the same head gasket thickness at the least.

What is the procedure you are currently using to tighten the head bolts?

IMO ring wear in 2 cyls is not the most likely  thing.


i was told that the head got all new valves and it was checked for warpage valve clearance was checked i was told it was all good to go but to just make sure to do the valve shims 

okay ill measure how much the pistons come up and see what they say.. and how i torq it down i go by what the Bentley says...? is that what you mean?

Reply #67July 06, 2012, 02:49:45 pm

745 turbogreasel

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Re: !979 Rabbit Diesel Need help!
« Reply #67 on: July 06, 2012, 02:49:45 pm »
Stretch bolts tighten differently form non-stretch ones, and the only torque number you had mentioned was 36 which isn't right.

So they didn't surface the head, replace guides, grind or replace valve seats, pressure test set valve face depth, set precup stickout, check for collapsed lifters...

Reply #68July 06, 2012, 09:38:19 pm

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #68 on: July 06, 2012, 09:38:19 pm »
Stretch bolts tighten differently form non-stretch ones, and the only torque number you had mentioned was 36 which isn't right.

So they didn't surface the head, replace guides, grind or replace valve seats, pressure test set valve face depth, set precup stickout, check for collapsed lifters...

haha no no they did they did! thats what i was told was all done to the head :)

haha they say to torque the head to 36 then once the engine is heated up go back and torque the head bolts to 57 or somthing like that i dont have bently in front of me.. i havent gotten the engine to even fire up so i havent been able to torque them to the high number yet?

Reply #69July 06, 2012, 09:47:42 pm

libbydiesel

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Re: !979 Rabbit Diesel Need help!
« Reply #69 on: July 06, 2012, 09:47:42 pm »
Where are you getting the head torque spec from?  The 1979 diesel Bentley says to torque in sequence to 22 ft lbs, then in sequence to 43 ft lbs, then in sequence to 61 ft lbs.  Then after 1000 MILES or 1500 KM in reverse sequence loosen all of them 30°.  Then in sequence tighten if cold to 61 ft lbs, if hot to 68 ft lbs. 

Reply #70July 06, 2012, 09:50:10 pm

libbydiesel

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Re: !979 Rabbit Diesel Need help!
« Reply #70 on: July 06, 2012, 09:50:10 pm »
Stretch bolts tighten differently form non-stretch ones, and the only torque number you had mentioned was 36 which isn't right.

A 79 doesn't have stretch bolts but regardless, 36 is not right. 

Reply #71July 09, 2012, 01:56:13 am

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #71 on: July 09, 2012, 01:56:13 am »
Where are you getting the head torque spec from?  The 1979 diesel Bentley says to torque in sequence to 22 ft lbs, then in sequence to 43 ft lbs, then in sequence to 61 ft lbs.  Then after 1000 MILES or 1500 KM in reverse sequence loosen all of them 30°.  Then in sequence tighten if cold to 61 ft lbs, if hot to 68 ft lbs. 

yes i re read the Bentley and i was doing it wrong.... that is all corrected now!

Reply #72July 09, 2012, 01:56:24 am

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #72 on: July 09, 2012, 01:56:24 am »
okay so this might be a dumb question and probably dumb of me to do... but i was thinking if maybe the valves were not closing all the way that compression was getting lost there... so i decided to take of the cam shaft so i knew forsure that the valves were closed and then i went and put on the compression tester i then went and cranked the block but nothing came up on the compression tester gauge why is this?

Reply #73July 09, 2012, 09:14:04 am

theman53

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Re: !979 Rabbit Diesel Need help!
« Reply #73 on: July 09, 2012, 09:14:04 am »
There probably isn't much to compress with both valves closed.

Reply #74July 09, 2012, 11:27:15 pm

vw-tim

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Re: !979 Rabbit Diesel Need help!
« Reply #74 on: July 09, 2012, 11:27:15 pm »
There probably isn't much to compress with both valves closed.

haha yeah i realized after thinking about it that you need air to get into the cylinders to create compression lol correct?

 

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