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Mon Feb 15, 2010 9:47 am

OK, Let me get your two cents on this. My Dad feels we have the time to fix my engine rather than replace it, so we'll be giving it a go and I'll post pictures here.

Right now, I have a 2.0 liter engine. On my last road trip, it made a valve clatter, so I pulled over in a rest area. I was losing power at the time. I figured out it was a valve issue (#3), so I removed he rocker arms and rod and tried to limp it back home on 3 cylinders. At first, it was going, well, but after 5 miles, it was running like crap. I pulled it over and towed it home the next day.

Now, it sits in my driveway. I can start it up, and it runs on 3 cylinders still. At low RPM, I get a light knocking. Not like a valve noise. Could be a piston slap. It could be something worse, but it isn't a "thunk" like a main bearing issue. If I rev it up in nuetral, the knocking goes away, but then comes back once the RPMs catch up with how much I stabbed the pedal? Does that make sense? I'm saying as it is revving, it is quiet, but once it reaches a revved state, the noise starts in again.

I'll be tearing it apart over the next day or so. But I'm curious as to whether there are any clues about what it might be. What kind of damage could you do running on three cylinders that would result in these symptoms? Just hoping for a sneak-peek at what I'm up against.

BTW, what does piston slap or a loose head sound like? Could the head have been loosened by removing the rocker arms?

Steve

Mon Feb 15, 2010 10:34 am

To tell you the truth, it sounds like you may have broken a valve, and that knock might be the remains of your broken valve stuck on the piston slapping up against the head.

Mon Feb 15, 2010 10:36 am

Wait no, nevermind, that knocking noise is probably from removing the rocker arms :?
The compression has no way to exit.
put your rocker arms back and a adjust those valves then see what happens.

Mon Feb 15, 2010 10:46 am

I agree and if the intake spring is the weaker of the two you would be burping exhaust into your intake.

Replace push rods, adjust valves, visually check valves while your there and then do a compression test.

edit did you pull the spark plug? Try that maybe first...

Mon Feb 15, 2010 12:45 pm

Boy, you guys could be right. Can't wait to get home and check into that. I think I remember that I did have a plug screwed in there though I remember discussion about taking it out. Waffling here, but IIRC, I did leave the plug in. I do remember when I ran it yesterday and shut it down, it let out a slow hiss after shut down, like a steam engine letting off pressure. Perhaps this was the compression leaking out. That could also explain a degradation of performance too...the build up of pressure didn't let one of my three remaining pistons work right either.

I'm going to take some pix tonight and get back to this thread.

Steve

Mon Feb 15, 2010 5:50 pm

Westy Steve wrote: Boy, you guys could be right. Can't wait to get home and check into that. I think I remember that I did have a plug screwed in there though I remember discussion about taking it out. Waffling here, but IIRC, I did leave the plug in. I do remember when I ran it yesterday and shut it down, it let out a slow hiss after shut down, like a steam engine letting off pressure. Perhaps this was the compression leaking out. That could also explain a degradation of performance too...the build up of pressure didn't let one of my three remaining pistons work right either.

I'm going to take some pix tonight and get back to this thread.

Steve

I love you guys! I just pulled the plug and you were right. It now makes a whooshing sound, but the knock is gone. After thinking it through, I guess since the plug was in, when the piston was on the downstroke, it was pulling the valves open, and they then snapped shut on the upstroke making that knocking sound. I might get out of this will just a new head, and likely at worst, a couple of new cylinders and piston heads.

Interestingly, when I tried to limp it back home, recompressing that air cause it to overheat and diesel until it died in a supermarket parking lot. But it started the next day easily. It is clear what was happening. The final hiss emitted from the engine was a big clue that it was trying to get rid of built up pressure. More later, gotta get to the store for groceries. But you guys are the best!

Steve

Mon Feb 15, 2010 6:01 pm

Just try doin' that w/ a modern day engine :)

Mon Feb 15, 2010 6:28 pm

Still get those rocker arms in there, and adjust the valves my friend, that loss of power could have been caused by a simple tight valve(s) in that cylinder, your engine may be fine.

Mon Feb 15, 2010 7:59 pm

Ah, now that one I know! When the bus broke down, I couldn't adjust out the valves...I'm familiar with that problem as I've had it before, and I'm pretty sure my head gave up its ghost.

Now, I've been laying in a wet driveway at night with a flashlight trying to figure out what head I need.

Very hard to read, but I'm 99% certain I was reading 021 101 371S, which is I think theoriginal head for an 1800. But I was told I had a 2.0 Liter engine and I'm running a GE case, so I'm pretty sure this head was re-machined to make it a 2.0 liter. I was also using hydraulic lifters. So does that mean those were machined into it as well?

The thing that has me mystified is though my number appears to be 021 101 371S, I was looking at where the exhaust manifold hooks up to the head and from the outside, it has a section of the pipe that is parallel. So is the pipe that hooks to the exhaust manifold from the outside a perfect circle, or an oval with parallel straight sections?

Since my head (apparently) started life as an 1800 or 1700 head that was converted to a 2.0 liter with hydraulic lifters, is it a safe assumption that I have round ports? So I need a round port 2.0 liter head with hydrualic lifters?

Thanks for any help.

Steve

Mon Feb 15, 2010 8:24 pm

1800 and 2000 heads are basicly identical. mildly different combustion chamber shape, possibly different valve sizes, but completly interchangable. a 1700 head has a smaller opening for the cylinder, and again is completly interchangeable if you cut it open, like flycutting open a bug head for 90.5 pistons, ya dig?
only 79 and newer buses have square ports, and you will know which you have teh second you unbolt yoru exhaust and compare. let me say that again, only 79 and newer buses SHOULD ave square, who knows what you have.

Mon Feb 15, 2010 8:26 pm

here is an easy photo to show the differences in the heads
type 4 engine identification (suburbanengine.com)

Mon Feb 15, 2010 8:57 pm

Thanks for the info. I've been doing my own sleuthing and ran across this:

http://www2.cip1.com/PhotoGallery.asp?ProductCode=VWC%2D021%2D256%2D091%2DM

This is the heat exchanger for the early Type IV. My confusion came from the fact that the outside of the pipe leading into the head does have a squared off appearance to it, though the head's numbers indicate it should be a round port because it's an early head. So it seems that I do need a round port 2.0 Liter head with the hydraulic lifters.

I need to get one ordered ASAP before I can even clear a warm, dry, place to tear it all apart.

Steve

Mon Feb 15, 2010 10:32 pm

Sounds like you would want to pull both heads when the engine gets out. And locate a reputable VW head man to do the work and keep the situation in good shape. And have him rebuild both heads fully and identical.

Tue Feb 16, 2010 7:12 am

That would definitely be the best way. But when my Dad got his Vanagon, it didn't run worth crap because the P.O. had put on a new head on one side only, but shimmed it wrong so the compression was way higher than the other. So we took cylinder pressure readings of the "old" side, and then used computer programs to calculate how the "new" side would have to be shimmed so that the cylinder pressure would match. It worked like a champ, and he hasn't changed it out yet after many miles.

So it does bring up an interesting question...is it so important to have new heads on both sides as long as your pressure tests are almost equal and he heads are valved approximately the same?

Steve

Tue Feb 16, 2010 8:45 am

The chamber volume may be different between another head if you just do one side.. To check the other side, you gotta pull it unless you assume its the same chamber volume as the bad one, which may not be a correct assumption.. I would not jut slap a reworked or new head on one side and ignore the other. While the motor is out, it just makes sense to get the whole top end checked out.. Get you pistons and jugs cleaned and checked, hone the cylinders, get new rings.. At the bare minimum, get both heads inspected and reworked/replaced.. One might get you by but the old one might go anytime.. Best handle it while you are down already.. Chamber volume, deck height and valves need to be the same on both sides, not approximately the same but you know that already :)..

Tue Feb 16, 2010 9:04 am

Just to be devil's advocate, what difference would it make as long as the compression (and therefore the compression ratio) was the same on both sides? Over time, they might degrade at different rates, but that can happen anyway, right?

Tue Feb 16, 2010 9:15 am

Static compression isn't the same as working compression which relates to actual chamber volume, the amount of charge and what power it produces, that's way different from what compression the rings produce while cranking with no combustion is taking place.

Just measure them all and sleep well afterwards.

Tue Feb 16, 2010 9:57 am

Westy Steve wrote: But when my Dad got his Vanagon, it didn't run worth crap because the P.O. had put on a new head on one side only, but shimmed it wrong so the compression was way higher than the other.
I know you are trying to do this one the cheap but you've already had to deal with a PO doing just one side and not doing a proper job.. Don't be that guy ;).. I probably would stay up at night thinking about that old head just waiting to go. They are one of the weakest links on a T4..

Tue Feb 16, 2010 10:26 am

... I predict you will find a lose/dropped exhaust valve seat has caused this problem.

Tue Feb 16, 2010 11:37 am

Westy Steve wrote: Just to be devil's advocate, what difference would it make as long as the compression (and therefore the compression ratio) was the same on both sides? Over time, they might degrade at different rates, but that can happen anyway, right?

The difference could...and usually is...LARGE. Different chamber shapes even of the same voulme create different breathing efficiencies. One may flow much more air than the other and one may hold a lot more heat than the other. In short...one head may produce different torque and horsepower than the other and will cause the engine to run rough and lopsided because of it. This whole scenario can happen when one head is rebuilt to a different level...or when two different head part #'s are used.

I have seen this issue several times. GEX is notorious for this issue. I have seen at least three engines come from GEX this way and they were NEVER able to be tuned properly with either stock L-jet or with twin carbs that had a balance pipe like stock solexes. Each head will flow differently and you will not be able to balance the carbs because of it. Ray