Author Topic: I have my pistons out (Read 4654 times)

Mexe · « **on:** March 21, 2008, 08:27:15 pm »

So on the advice of my mechanic I took my pistons out to do my rod bearings and the rings on the pistons. He said my main bearings will not be a problem and to not touch them so the crank is still in the car but is there anything else I should do while this is out? It is a 1.6L TD and I am intercooling it and upping the boost.

Vincent Waldon · « **Reply #1 on:** March 21, 2008, 08:53:04 pm »

Yup, your main bearings !!

The crank does not need to come out to do them and they're cheap... you've come this far... go that one more step and have fresh bearings all around. A flexible plastic putty knive cut to the same width as the bearing will push them out.. the job will take 10 minutes.

The other important thing to do is to deglaze the cylinder walls... new rings against glazed bores won't do much for your compression.

Mexe · « **Reply #2 on:** March 21, 2008, 08:57:04 pm »

How do I deglaze the cylinder walls? Mine are pretty shiny right now. Also aren't the main bearings made of 2 pieces so wouldn't that be a bit harder to push out properly?

RabbitJockey · « **Reply #3 on:** March 21, 2008, 09:25:42 pm »

wait till you have the motor running again and pour sand into the intake and rev it up. haha just kidding , you just need to hone the bores.

Vincent Waldon · « **Reply #4 on:** March 21, 2008, 09:30:33 pm »

Yup... the bearings are in two halves. The first half will come out when you remove the bearing caps. The second half is what you push out with the plastic putty knife... one little tap and it will swing around and practically fall into your hand.

To deglaze you need a deglazer... also called a hone. Most automotive stores carry them... Napa or Autozone for instance. The conventional kind has three rectangular stones that are spring loaded and rotated using an electric drill. Your machinist might lend you his ?? You need it for all of 5 minutes, but if you don't deglaze your new rings will not seat and your compression will likely be worse than with the old rings.

dubbinchris · « **Reply #5 on:** March 21, 2008, 11:41:33 pm »

Quote from: "Vincent Waldon"

Yup... the bearings are in two halves. The first half will come out when you remove the bearing caps. The second half is what you push out with the plastic putty knife... one little tap and it will swing around and practically fall into your hand.

To deglaze you need a deglazer... also called a hone. Most automotive stores carry them... Napa or Autozone for instance. The conventional kind has three rectangular stones that are spring loaded and rotated using an electric drill. Your machinist might lend you his ?? You need it for all of 5 minutes, but if you don't deglaze your new rings will not seat and your compression will likely be worse than with the old rings.

I always thought you had to clean the cylinders really well after honing or is deglazing and honing different?

Vincent Waldon · « **Reply #6 on:** March 22, 2008, 12:05:54 am »

Yeah, they're pretty much the same imho... the tool is called a hone, and to me "deglazing" is a light pass with a hone to break the glaze with nice 45 degree scratches, while "honing" usually implies removing a fair amount of metal (to get rid of vertical grooves, for example).

Either way you're right... thorough cleaning is needed... so the due-diligence way to do the job is to pull and then completely disassemble the engine, deglaze/hone, and then clean everything before reassembly... replacing seals, intermediate shaft bearings, etc while you're in there.

Having said that, if you are just taking a few passes with the hone to break the glaze it is possible to wipe up most of the debris with a rag and then hose the heck out of everything with spray brake drum cleaner and compressed air. Brake cleaner and compressed air can get things remarkably clean... and a oil and filter change after 5 minutes of initial run-in is a good idea too. Covering the exposed bits of the crank with plastic and leaving the main bearing caps in place will help keep stuff out of harms way during cleaning as well.

I'm ashamed to admit :oops: I was forced to do my gasser Jetta this way last year due to extreme time constraints (car could only be down for a weekend)... but so far she has broken in nicely and I found absolutely no grit in the oil at the 5 minute mark. I make myself feel better by calling it an experiment.

It's absolutely cheating... no doubt... but in my mind worse cheating would be to do the rings and not deglaze. :wink:

jimfoo · « **Reply #7 on:** March 22, 2008, 12:25:57 am »

Quote from: "Vincent Waldon"

Yup... the bearings are in two halves. The first half will come out when you remove the bearing caps. The second half is what you push out with the plastic putty knife... one little tap and it will swing around and practically fall into your hand.

Except the thrust bearings, which can't be done without removing the crank if you have the 3 piece bearings, which you should. If you have the 1 piece bearing/thrust bearing, you should really pull the crank and replace it with the 3 piece type.

Vincent Waldon · « **Reply #8 on:** March 22, 2008, 12:54:35 am »

Ah... I done pulled the three piece with the crank in place as well... little nudge from a very narrow piece of stiff plastic (mighta used a piece of icecream pail?) and each piece wrapped around its respective thrust face of the crank and fell into my hand.

But yes, you really should pull the crank... regardless. I can hear the entire VW GTD forum membership from here as they shriek in outrage :shock: at the idea of deglazing with the crank in place... and they have a point.

jimfoo · « **Reply #9 on:** March 22, 2008, 12:57:55 am »

How is that, unless AAZ ones are different? Mine had a tab that locked them in place from rotating.
As far as removing bearings, I was taught to use a thin cotter pin bent into the appropriate t shape, put in the oil hole in the crank, then rotate it to get the bearing half out.

Vincent Waldon · « **Reply #10 on:** March 22, 2008, 01:31:40 am »

On the ones I pulled the tab was much much thinner than the thrust bearing itself, so with a bit of freeplay it could move sideways a bit and then rotate out. In fact, as I think back, it seems to me that they were more of a dimple than an actual tab... a bit of a protrusion but very slight, in both axis. Would have been gasser 1992 original bearings.

Didn't notice on the last set I did (an AAZ as luck would have it) since the crank was already out... being an AAZ of course you have to have the crank out... sadly not just to do the bearings. Or perhaps I vaguely remember that the tabs were for the cap side of the bearing on the AAZ ?

I'd read about the "use the oil hole" method and tried it but rotating the crank from under the car was a pain and I was worried about scratching the journal where the bearing sits (not that it probably matters) or jamming the pin and damaging the crank. Then I read about using a plastic putty knife as a chaser and it was a proverbial piece of mythical cake.

I didn't take pictures (since I never intended to repeat the performance) but this guy did... although it doesn't look like his Golf had three-piece thrust bearings or he would have mentioned it:

http://www.boompa.com/guide/main-bearing-replacement-the-easy-er-way/114

Sorry OP we got a bit off topic here... ;-)

Mexe · « **Reply #11 on:** March 22, 2008, 02:02:58 am »

No it is good to read. I am just wondering if I should really attempt it. I cannot take the tranny off and from reading you need to in order to take the crank out. I also am afraid of messing up pushing the bearings out and then having to go do that. I guess the best bet is to think about it, I will talk to my mechanic as I will most likely run into him Sunday and see what he thinks about it. He has been working on VW's for years and says he has not seen main bearings being a failing point as they do not get abused like rod bearings do.

Vincent Waldon · « **Reply #12 on:** March 22, 2008, 02:12:57 am »

I hear ya... sometimes you can go too far and regret it.

Diesel bearings take more of a pounding than gasser bearings, but in actual fact the truly scientific way to do this is to measure the bearings first using Plastigauge... and then decide what to do. You could take 5 minutes and measure a couple of representative bearings without any risk of messing anything up, and then see... your bearings may in fact have tons of life left in them.

Lots of us are just in the habit of replacing them on spec... rings are worn, you have the engine apart... the bearings are cheap... one less thing to have to pull it apart for later.

Either way, let us know what you find out !!

Vince

Mexe · « **Reply #13 on:** March 22, 2008, 02:22:28 am »

For sure. The thing is the engine was still running really well when I took it apart. I only started to do this to put in a metal head gasket and one thing led to another and I got to the point where I was just going to do as much as I could without having to take the engine out of the car or remove the tranny. The pistons are easy enough to do, so I will look at the mains too, see if it is possible for me to do now or if I should just let them be.

smutts · « **Reply #14 on:** March 22, 2008, 07:54:12 pm »

Quote from: "Trev0rbr"

wait till you have the motor running again and pour sand into the intake and rev it up. haha just kidding , you just need to hone the bores.

GENIUS!