VW T4 Forum - VW T5 Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
39 Posts
Discussion Starter #1
Hey T4 Community,

Thanks for reading. I know its long but I would rather have too much information than come in missing important pieces.

I am in the process of rebuilding my 2.4 AAB diesel engine out of a ’93 Eurovan (in Canada here). The pistons are in (and torqued) and I am trying to measure deck protrusion before fitting the appropriate head gasket. However, being that this is my first rebuild and first time using a dial gauge/indicator to measure piston protrusion, I am in need of assistance.

Here is some brief background for context:
Original engine is a ’93 2.4 AAB but I had to scrap the block and replaced it with a ’97 AAB block. I’m still using the original crank and conrods from the ’93 though (inspected and balanced). I had the block mating surface decked and the cylinders bored and honed at a local shop. New oversized (80.010) Kolbenschmidt pistons and rings installed.


Ok, so as per the VW Service Repair Manual, I am using the following as a guideline for which head gasket (based on notches) to fit:
- Up to 0.86 mm = 1 notch
- 0.87 mm – 0.90 mm = 2 notches
- Above 0.90 mm = 3 notches

The values I got for piston protrusion are as follows. I took 4 measurements ( 2’oclock, 4’oclock, 8’oclock and 10’oclock) from each piston and referenced it against the deck height:

1. 0.699 mm | 0.686 mm | 0.711 mm | 0.711 mm AVG 0.702 mm
2. 0.668 mm | 0.762 mm | 0.683 mm | 0.724 mm AVG 0.709 mm
3. 0.706 mm | 0.724 mm | 0.757 mm | 0.757 mm AVG 0.736 mm
4. 0.739 mm | 0.706 mm | 0.742 mm | 0.686 mm AVG 0.718 mm
5. 0.533 mm | 0.648 mm | 0.610 mm | 0.691 mm AVG 0.621 mm

I am surprised that all of the readings are as low as they are, especially considering the block was resurfaced. But, I am ESPECIALLLY concerned about the piston 5 readings.
Any thoughts? Could it be a bent rod? I want to do the build right and will take the time I have to in order to do so.

Thanks in advance for your help.
 

·
Registered
Joined
·
2,324 Posts
Hey T4 Community,

Thanks for reading. I know its long but I would rather have too much information than come in missing important pieces.

I am in the process of rebuilding my 2.4 AAB diesel engine out of a ’93 Eurovan (in Canada here). The pistons are in (and torqued) and I am trying to measure deck protrusion before fitting the appropriate head gasket. However, being that this is my first rebuild and first time using a dial gauge/indicator to measure piston protrusion, I am in need of assistance.

Here is some brief background for context:
Original engine is a ’93 2.4 AAB but I had to scrap the block and replaced it with a ’97 AAB block. I’m still using the original crank and conrods from the ’93 though (inspected and balanced). I had the block mating surface decked and the cylinders bored and honed at a local shop. New oversized (80.010) Kolbenschmidt pistons and rings installed.


Ok, so as per the VW Service Repair Manual, I am using the following as a guideline for which head gasket (based on notches) to fit:
- Up to 0.86 mm = 1 notch
- 0.87 mm – 0.90 mm = 2 notches
- Above 0.90 mm = 3 notches

The values I got for piston protrusion are as follows. I took 4 measurements ( 2’oclock, 4’oclock, 8’oclock and 10’oclock) from each piston and referenced it against the deck height:

1. 0.699 mm | 0.686 mm | 0.711 mm | 0.711 mm AVG 0.702 mm
2. 0.668 mm | 0.762 mm | 0.683 mm | 0.724 mm AVG 0.709 mm
3. 0.706 mm | 0.724 mm | 0.757 mm | 0.757 mm AVG 0.736 mm
4. 0.739 mm | 0.706 mm | 0.742 mm | 0.686 mm AVG 0.718 mm
5. 0.533 mm | 0.648 mm | 0.610 mm | 0.691 mm AVG 0.621 mm

I am surprised that all of the readings are as low as they are, especially considering the block was resurfaced. But, I am ESPECIALLLY concerned about the piston 5 readings.
Any thoughts? Could it be a bent rod? I want to do the build right and will take the time I have to in order to do so.

Thanks in advance for your help.
before you panic about the protrusions,
whats the tolerences for the components? conrod C-C length, piston hight, bearing clearance crank main / bigend & conrod 'little-end' / wristpin) & even the crankpin grind offset can affect totals (also, how accurate was the deck-face skim? can get taper in such with a mill thats too short;) )

is it possible that you have the bad luck to assemble 'short' components togther to make number 5:*

Rich.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #3
Hey Rich,



Thanks for the message. It sounds like I should start looking into those component tolerances. I'm also working to get a straight edge so I can check the deck-face for taper. Thanks for that thought.


I'm also going to get a deck-bridge and use that with my dial indicator to re-measure the protrusions. As I was using a magnetic stand with the adjustable arms, I'm hoping another round of measurements with a different mounting tool will illuminate if user error is contributing to the situation.


I guess it is possible that I had some bad luck and assembled "short" components together, for sure. My next question would be if I get the same measurements, should I be concerned about putting the cylinder head on? Like, could I just go ahead and be fine with a compression ratio that is off for cylinder 5?


Cheers,

Will
 

·
Registered
Joined
·
2,324 Posts
could I just go ahead and be fine with a compression ratio that is off for cylinder 5?
that's working on the assumption that everything else in the world is perfect? theoretical compression is one thing, actual (with a pressure-guage) will be diferent as will the cylinders port effenecy (got access to a flow-bench?), injector & pump pressures / delivery volume etc:confused:

from a quick look at the hight diferences, 0.1mm is 0.0039" (yep, I work in Imperial at home & metric in work - throwback to my apprentaceship 30 years ago in a machine-shop with older lathes, mills & even micrometers! so all drawings had to be convertedLOL: ), doubt that would alter the compression on a diesel engine by enough to cause issues:*

personally, I'd run it as you've got issues getting replacements or used spares where you live:(
although, over here spares are common (plenty of dead vw'sI: ) I have a dead 2.4D engine outside my shed that was removed from a mates t4 and replaced with a 1.9tdi conversion - more power, better economy, cruise control & cheaper maintananceI:


anyway, once you have it built, installed & running you'll not worry about any possible imballance, just enjoy the 5-cylinder soundtrackA:


Rich.
 

·
Registered
Joined
·
39 Posts
Discussion Starter #5
I thought I would post an update in the event that it is helpful to someone. I ended up taking the block to my machinist to sort it out. They found that rod # 5 was bent. Thankfully I had a spare rod they could use :)
 
1 - 5 of 5 Posts
Top