Type IV bottom end knocking

[hercdriver]

I've got a type IV ? liter in my 75 bus that is making a rhythmic tapping sound that seems to come from the bottom of the case.

I don't drive the bus much and have been trying to get it into proper working order since I bought it this past summer. It should be a 1.8 liter, but the fan shroud indicates that it's a 1.7 liter. It should also be F/I, but has been converted to progressive carburetor. In addition, last fall you guys helped identify what seemed to be a fallen hydraulic lifter (horribly loud ticking noise that went away after a five minute engine run).

I am still in the crawling stages of air-cooled VW ownership and live in a bit of a vacuum in relation to other older VW's. I have relied heavily on this and other VW sites to supplement the Bentley manual and my own exploration. Having said that, nothing replaces an experienced VW mechanic. Which brings me up to yesterday. While trying to diagnose a starting issue (turned out to be a weak battery and corroded terminals), I had a long time friend come over to help me out. Although he's not a VW guru, he has rebuilt several VW engines and specializes in air-cooled aircraft engines. When he heard the engine start, he immediately said that something sounded off. This was news to me, since the engine sounded that way since I bought it. After we let it run a few minutes, I could hear what he was talking about. It's a low rhythmic tapping that occasionally will go away for few moments. He seemed convinced that it was a rod bearing on it's way out. Needless to say that's not what I wanted to hear.

I've been watching the rebuild threads on this forum, and quite frankly am a bit gun shy of taking on full rebuild. My friend said that it was not a big deal and that we could get away with new main bearings, turn the crank, and piston rings (all for $200-300). That seems way too simple and inexpensive based on what I've been reading.

Here are some pictures of todays work.......

Here's a picture of the mouse nest I found on top of the #4 cylinder.


The plugs are in reverse order in the picture from left to right (4-3-2-1)


A close up of one of the plugs. I think it looks rich.


I also did a compression test. I was encouraged by the results. Although number 3 seems a bit high. It also makes me question why they are so different from each other.

Cylinder #1 110 psi
Cylinder #2 165 psi
Cylinder #3 175 psi
Cylinder #4 150 psi

Thanks for wading through this ramble. To summarize.......

1. What's next?
2. Would you tear it down?
3. Does $300 sound reasonable for a bare bones bottom rebuild?


Dave

[Amskeptic]

I've got a type IV ? liter in my 75 bus that is making a rhythmic tapping sound that seems to come from the bottom of the case.

Warm? Cold?
At idle? Under load? At release of load?
Steady? Intermittant?
Go away with foot on clutch?
Oil viscosity?
These engines have a lot of reciprocating noise on a good day.
Colin

[hercdriver]

I've got a type IV ? liter in my 75 bus that is making a rhythmic tapping sound that seems to come from the bottom of the case.

Warm? Cold? Seems to be both
At idle? Under load? At release of load?I notice it more at idle. To be honest, it's hard to hear when driving.
Steady? Intermittant?mostly steady, although it does seem to quiet down as rpms pick up slightly from idle
Go away with foot on clutch? clutch doesn't effect it
Oil viscosity? 10W30
These engines have a lot of reciprocating noise on a good day.
Colin

Here's a video of the beast in question. The inner slacker in me is holding out that the engine is fine and that it was just an over zealous diagnosis.

http://www.youtube.com/watch?v=eGcbQY8QQaQ

The very end of the video has has the best recording of the sound I'm trying to describe.

[Amskeptic]

I've got a type IV ? liter in my 75 bus that is making a rhythmic tapping sound that seems to come from the bottom of the case.

Warm? Cold? Seems to be both
At idle? Under load? At release of load?I notice it more at idle. To be honest, it's hard to hear when driving.
Steady? Intermittant?mostly steady, although it does seem to quiet down as rpms pick up slightly from idle
Go away with foot on clutch? clutch doesn't effect it
Oil viscosity? 10W30
These engines have a lot of reciprocating noise on a good day.
Colin

Here's a video of the beast in question. The inner slacker in me is holding out that the engine is fine and that it was just an over zealous diagnosis.

http://www.youtube.com/watch?v=eGcbQY8QQaQ

The very end of the video has has the best recording of the sound I'm trying to describe.

Definitely not good.
Rod bearing if you can get a sharp knock when you release the gas at higher rpm.
Collapsed piston if it is worse cold than hot and worse slower rpm than higher rpm.
IMACO
(In My Auditorily-Challenged-Opinion)

[hercdriver]

Definitely not good.
Rod bearing if you can get a sharp knock when you release the gas at higher rpm.
Collapsed piston if it is worse cold than hot and worse slower rpm than higher rpm.
IMACO
(In My Auditorily-Challenged-Opinion)

I was afraid you'd say that. Any chance you'll be swinging through western Pennsylvania before the end of the 2010 tour? I'd really like to do the visit we had planned last August.

[Amskeptic]

Definitely not good.
Rod bearing if you can get a sharp knock when you release the gas at higher rpm.
Collapsed piston if it is worse cold than hot and worse slower rpm than higher rpm.
IMACO
(In My Auditorily-Challenged-Opinion)

I was afraid you'd say that. Any chance you'll be swinging through western Pennsylvania before the end of the 2010 tour? I'd really like to do the visit we had planned last August.

Pester me inbox 'round late August. What are your options as far as dealing with this. Are you ready to do your own rebuild?
Colin

[hercdriver]

Are you ready to do your own rebuild?
Colin

Funny you should ask. I quit running the engine because I was told it may cause more damage. (Outside of the knocking sound, I also had a pretty bad oil leak.) Faced with the inevitable fact that this was going to turn into a tear down, I decided to do it.

Although the veterans here may have a good laugh at how much time it took me to pull the engine out, I managed to do it alone without causing any more damage than it already had. The hardest part of the whole job was getting the engine tin screws out. Even after a few days of PB Blaster, tapping with a hammer, heat, and a few sentence enhancers I had two screws that refused to come out of the drivers side head. Once the tin was removed, it was immediately apparent why this whole learning experience was worth my time. I previously posted a picture of a mouse nest that I pulled out through the spark plug holes in the cooling tin. At the time I thought I had removed most of it.

Here is the other half that I missed.


Had I kept running the engine with all of that debris, the engine would have cooked that head at the very minimum.

After pulling the heads, I found the answer to what kind lifters I have.
Hydraulic lifters! But this is a "CB" engine code that means it's a 1.7 liter right? Should be solid lifters? Push rods are aluminum. Shouldn't they be steel if you have hydraulic lifters?


Now the heads. The 1/2 head looks like it was recently installed. Which surprised me since it was the number 1 cylinder that was the lowest compression. The other head wasn't so pretty the 3/4 head has some pretty good chunks taken out of the combustion section of the head.


Here's a closer look of the damage on number 4.



I'll post up some more pics of the main bearings shortly.

Comments/words of wisdom are greatly appreciated. Let me know what you think.

Thanks,
DaveIcantBelieveIjustToreUpThisEngine

[hercdriver]

As promised here are the pictures of the bearings. At this point I'm glad that I tore it down. I'm just concerned that this is much more than a ground crank and new bearings.

Would it be safe to say I'm looking at....

Line bore
New cam
New Bearings
Head work
Crank turned
Rods and Pistons balanced

Anything else?

Can anyone confirm that this is a 1.7 crank and rods? This engine has been rebuilt at least once before and I'd like to be sure of what I'm working with.

[chitwnvw]

The cam doesn't look too bad.

Was there debris in the head, that damage looks like a head of a valve was banging around in there for a while.

To determine your engine size, 1.7s have 90 mm across pistons, 1.8s and 2.0s have 93s. 2.0s crank has more travel, the piston travels more up and down to give you the extra displacement. I don't know off of the top of my head the difference between the offsets of the crank journals but I can't imagine it would be too hard to find out. I'd determine if you have a 1.7, 90 mm piston, and if not then determine whether you have 1.8 or 2.0.

[hercdriver]

Chit,

I took a look at the pistons and found....

SPO .03 ------------------------------- 89.97
<- ------------------------------------- Y16B
-------------------------------------------SK

Looks like 1.7 liter pistons. Which would match the case. The push rods are aluminum which should also be correct for this engine. The lifters are hydraulic however. The cam is unknown, but is showing signs of hydraulic lifter cross hatching across the lobes. With the wear and unknown specs, I decided to order a stock cam and solid lifters. Is it a waste of resources on this bare bones rebuild? I don't know. What I do know, is that something wasn't playing well in this engine and this seems like an obvious variable to eliminate.

I do have a question regarding the case. I have two opinions and respect both.
The first is.....That the probable cause of the knock was a worn main bearing. And that a line bore maybe in order. (the main bearing did show signs of uneven wear/shine).
The second opinion is....... that the main bearing didn't look bad and that type 4 engines very rarely need line bored. (he seemed to believe the hydraulic lifters were more of an issue).

Any thoughts?

[hercdriver]

Was there debris in the head, that damage looks like a head of a valve was banging around in there for a while.

The piston and cylinder looked almost new. I'm thinking that the head dropped a valve and they rebuilt the engine without cleaning up the damage.

[hercdriver]

Dave:

A BIG Negatory on the line bore UNLESS it's proven that you need one AND the service provider also provides the requisite bearings in the proper size. The pic of your crank and the pic of the case with the #2 main still in the saddle says it's good to go - looks d*mn near new, and usually #2 will show the wear first of all the mains. BTW - it's a 1.7L 66mm crank and associated rods. Big ol' balancing knob on top of the rod little end tells the story on that, the 2.0L rod lacks the knob... Wouldn't hurt to pop the rods off and check the rod bearing condition too - betcha $5-to-a-hole-inna-doughnut they're as good as that #2 main But if not - now is the best time to find out you need to drop extra coin for rod bearings.

I'm not going to have anything turned unless it's out of spec. Good to know about the rod size (one more piece of the puzzle has been put in place). I am replacing the bearings (main/rod/cam) since they case is open and I still haven't found the source of the knock.

Cam looks good, there's no divot on the lobe - change it only if you want to and have a few extra fitty dollar bills burning a hole in your pocket for anew one and matching lifters. Hope you marked the lifters out of their bores so they can be returned to their homes; I would expect the lifters to show little (if any) undue wear considering the condition of everything else. Push rods really "should" be the steel ones for a hydraulic application, and it's a nice touch to ditch the inter-rocker arm spacer springs as-used-on-the-solid-lifter engines for the solid spacers as-used-on-the-hydraulic-lifter engines. Odd that the one cam bearing is showing a touch of copper, but WTF? At least cam bearing sets are easier to find right now that T4 mains.

I think I am going to splurge on a new cam solid lifters. At this point it seems to be the biggest suspect in my original problem. It's also hard to tell in the pictures, but one of the lobes is showing some signs of wear. I'd also like to use solid lifters to take it back to stock.

A Gigantic D*ck-Four on the headwork... That is one messed up chamber on your #4. Something got s*cked in there, bounced around and then looks like it got spat out. Either that, or all that DID happen and then was never repaired properly. I think it was just never repaired properly.

If the crank spec's out OK - no need for needing it ground unless you like to spend money unnecessarily...No worries there. That's my opinion as well.

While it is a nice thought to have the rods and pistons balanced - it's a total waste of time/money if you DON'T get the entire rotating assembly (meaning impeller/crank/flywheel/pressure-plate) done to go along with it. That #2 main bearing will love you for it, and in general just be a total pleasure to drive vs a non-balanced bucket o' bolts.

I'm glad you mentioned having it balanced. I asked and was told that unless you're building a high rev engine, it's a waste of $. It makes sense to me to do it, but I'm not sure what the cost benefit is. At this point my objective is to build an engine that I can trust to take my family on a couple hundred miles on a road trip a hand full of times every summer. In five years (maybe ten) I'd like to do a proper rebuild and upgrade (2.0, hydraulic lifters, Camper Special, F/I).

If I do have it balanced, how much would expect to pay for the service? Can you really tell the difference when driving?

Thanks for the feed back! If I've responded with something that seems off, please raise the bullsh%t flag. I'm taking in a lot of suggestions and opinions right now and have yet to decide which are closer to the truth.

[Amskeptic]

Dave:

A BIG Negatory on the line bore UNLESS it's proven that you need one AND the service provider also provides the requisite bearings in the proper size. The pic of your crank and the pic of the case with the #2 main still in the saddle says it's good to go - looks d*mn near new, and usually #2 will show the wear first of all the mains. BTW - it's a 1.7L 66mm crank and associated rods. Big ol' balancing knob on top of the rod little end tells the story on that, the 2.0L rod lacks the knob... Wouldn't hurt to pop the rods off and check the rod bearing condition too - betcha $5-to-a-hole-inna-doughnut they're as good as that #2 main But if not - now is the best time to find out you need to drop extra coin for rod bearings.

I'm not going to have anything turned unless it's out of spec. Good to know about the rod size (one more piece of the puzzle has been put in place). I am replacing the bearings (main/rod/cam) since they case is open and I still haven't found the source of the knock.

Cam looks good, there's no divot on the lobe - change it only if you want to and have a few extra fitty dollar bills burning a hole in your pocket for anew one and matching lifters. Hope you marked the lifters out of their bores so they can be returned to their homes; I would expect the lifters to show little (if any) undue wear considering the condition of everything else. Push rods really "should" be the steel ones for a hydraulic application, and it's a nice touch to ditch the inter-rocker arm spacer springs as-used-on-the-solid-lifter engines for the solid spacers as-used-on-the-hydraulic-lifter engines. Odd that the one cam bearing is showing a touch of copper, but WTF? At least cam bearing sets are easier to find right now that T4 mains.

I think I am going to splurge on a new cam solid lifters. At this point it seems to be the biggest suspect in my original problem. It's also hard to tell in the pictures, but one of the lobes is showing some signs of wear. I'd also like to use solid lifters to take it back to stock.

A Gigantic D*ck-Four on the headwork... That is one messed up chamber on your #4. Something got s*cked in there, bounced around and then looks like it got spat out. Either that, or all that DID happen and then was never repaired properly. I think it was just never repaired properly.

If the crank spec's out OK - no need for needing it ground unless you like to spend money unnecessarily...No worries there. That's my opinion as well.

While it is a nice thought to have the rods and pistons balanced - it's a total waste of time/money if you DON'T get the entire rotating assembly (meaning impeller/crank/flywheel/pressure-plate) done to go along with it. That #2 main bearing will love you for it, and in general just be a total pleasure to drive vs a non-balanced bucket o' bolts.

I'm glad you mentioned having it balanced. I asked and was told that unless you're building a high rev engine, it's a waste of $. It makes sense to me to do it, but I'm not sure what the cost benefit is. At this point my objective is to build an engine that I can trust to take my family on a couple hundred miles on a road trip a hand full of times every summer. In five years (maybe ten) I'd like to do a proper rebuild and upgrade (2.0, hydraulic lifters, Camper Special, F/I).

If I do have it balanced, how much would expect to pay for the service? Can you really tell the difference when driving?

Thanks for the feed back! If I've responded with something that seems off, please raise the bullsh%t flag. I'm taking in a lot of suggestions and opinions right now and have yet to decide which are closer to the truth.

Do not make business decisions on what you want/don't want to do with this rebuild, based on sounds that you once-upon-a-time heard when it was running.

You make all decisions based on what is in front of you, by looking at the surface condition and measuring the current clearances.

That engine *looks* to be in good condition minus traumatic injuries. The #4 rod has to be checked for bend or twist with that combustion chamber damage. They are solid excellent rods but you have to check.

New cam bearings are too easy to replace not to replace, but remember that you must measure end-play of the camshaft, there are horror stories out there of .010 + banging around.

I recommend that you balance the snot out of every engine you run across, these cases are not growing on trees and we must make decisions for longevity of the hobby. Save the case with a competent balance job if you can swing it.
Colin
(P.S. I have seen composite solid lifters out there. Make sure these are real hydraulics before you indict them. Disassemble one to see if the control valve is actually in there)

[chitwnvw]

Save your cam gear!!!

[hercdriver]

Do not make business decisions on what you want/don't want to do with this rebuild, based on sounds that you once-upon-a-time heard when it was running. I'm not sure I understand this statement. Like it or not, I don't have an unlimited budget to do this to the highest standard. Although, it is my intention to do this as well as I possibly can with the aid of those who've already traveled this road. My assumption about once-upon-a-time was that there was a problem to track down and that noise was a clue to the source of that problem.

You make all decisions based on what is in front of you, by looking at the surface condition and measuring the current clearances. I'm trying to do just that. I'm also trying to sift through different opinions to whether something is a miss or not. My current marching orders for the shop that has my case, crank, cam, and heads are to measure all before we decide what to replace.

That engine *looks* to be in good condition minus traumatic injuries. The #4 rod has to be checked for bend or twist with that combustion chamber damage. They are solid excellent rods but you have to check. To my untrained eye, I would agree it looks like its in pretty good shape. I'm convinced that the damaged to the #4 head was previous damage before the last rebuild (I've given the machine shop the okay to repair the head damage). My goal now is not to repeat the errors of the last build. I think you're right about the checking the rod out.

New cam bearings are too easy to replace not to replace, but remember that you must measure end-play of the camshaft, there are horror stories out there of .010 + banging around. I'm familiar with the end play of the crank being set to .004, but haven't come across the tolerances of the camshaft yet.

I recommend that you balance the snot out of every engine you run across, these cases are not growing on trees and we must make decisions for longevity of the hobby. Save the case with a competent balance job if you can swing it. Your wish is my command. I called the shop tonight and told them to reuse the cam if it's within tolerance and to balance the crank/flywheel/pressure plate. I will also have him weigh and balance the pistons/rods.
Colin
(P.S. I have seen composite solid lifters out there. Make sure these are real hydraulics before you indict them. Disassemble one to see if the control valve is actually in there)
If these are composite solid lifters, would you use them?
If they are Hydraulic lifters, would you use them or replace the pushrods (I didn't keep track of which place they came out of - I assumed at the time that they needed replaced)
I'm still inclined to get a new set of solid lifters. Is there a pitfall in this route?