TheSamba.com :: View topic - Rattle can noise during acceleration and load

Tue Apr 30, 2013 5:51 am

I have a 74 standard beetle that i daily drive and this morning on the way to work I noticed a rattle can noise of u will coming from the middle to tear of the car!! I was running a little behind so I was of course running a little harder than my everyday cruise but I only noticed it when I would accelerate or while I was climbing a hill and trying to hold the same speed! Hole sitting at an idle or out of gear there is no sound!! Only when acceleration and loa and the sound was more apparent when I was in 3rd and 4th gear an maybe that was just because I am in those gears longer I'm not sure!! Any and all help would be greatly appreciated

Tue Apr 30, 2013 6:00 am

That's called detonation. It sounds like your timing is too far advanced.

Tue Apr 30, 2013 6:12 am

But I don't hear the noise when I'm warming the car up or revving the engine

Tue Apr 30, 2013 6:58 am

Onewheeler wrote: But I don't hear the noise when I'm warming the car up or revving the engine
That's because detonation happens mostly under load. It's a result of incorrect timing or an overheating issue. Check your timing.

Tue Apr 30, 2013 7:43 am

I have a 1600 dp with a full electronic 009 distributor. What's should my timing be set at??

Tue Apr 30, 2013 7:55 am

Onewheeler wrote: I have a 74 standard beetle that i daily drive and this morning on the way to work I noticed a rattle can noise of u will coming from the middle to tear of the car!! I was running a little behind so I was of course running a little harder than my everyday cruise but I only noticed it when I would accelerate or while I was climbing a hill and trying to hold the same speed! Hole sitting at an idle or out of gear there is no sound!! Only when acceleration and loa and the sound was more apparent when I was in 3rd and 4th gear an maybe that was just because I am in those gears longer I'm not sure!! Any and all help would be greatly appreciated

Check your VOLTAGE REGULATOR. I am getting the same kind of sound from my VR under exactly the same kind of conditions. Especially at higher speeds like on the highway. Press the gas to try to go faster, no acceleration and that VR rattles and pops. Took me a while to figure out where it was coming from. No one on here has been able to explain it yet. Still haven't figured out whether there is a deeper cause to the problem.

Tue Apr 30, 2013 8:12 am

Onewheeler wrote: I have a 1600 dp with a full electronic 009 distributor. What's should my timing be set at??

Out of curiosity, how is the car currently timed?

Tue Apr 30, 2013 8:28 am

Might just be your shift rod bushing and/or shift rod coupling is shot and you're getting vibrations at higher rpm's. Especially if it's a tinny rattle.

Remove the shifter and check out the slop.

Tim

Tue Apr 30, 2013 8:31 am

Anytime you have to use a 009, you have to time it using a real timing light so that when all of the centrifical advance is in the timing should be 28-32º BTDC. That happens about 3000-3500 RPMs.

That pinging noise you hear is $100 bills flying out of your wallet for a new engine if you don't fix it soon.

Tue Apr 30, 2013 8:50 am

So by setting the timing somewhere in the 28 to 32 degree range I should get rid of the noise?? And if I have it in the higher rpm there is no noise until I try to accelerate or hold that speed while climbing a hill!! And if it is a timing issue what is causeing the noise?? Sorry fellas still a little young in the mechanics side of the vw but everyday brings new problems!!! Lol

Tue Apr 30, 2013 9:05 am

Detonation, in very simple terms, is when the compressed fuel in the cylinder burns before it is supposed to.

How are you timing your engine?

Tue Apr 30, 2013 9:26 am

Onewheeler wrote: So by setting the timing somewhere in the 28 to 32 degree range I should get rid of the noise?? And if I have it in the higher rpm there is no noise until I try to accelerate or hold that speed while climbing a hill!! And if it is a timing issue what is causeing the noise?? Sorry fellas still a little young in the mechanics side of the vw but everyday brings new problems!!! Lol

Onewheeler, PLEASE trust me on this. before you do anything around the engine compartment CHECK YOUR VOLTAGE REGULATOR. I am not guaranteeing 100% that this is the noise but from your description it sure sounds like EXACTLY the same problem I am having. Everyone else on here is thinking you are describing an engine pinging or whatever but I bet it sounds more like a rapid popping sound inside a metal canister.
Now here is the problem- I don't know what is causing it to do this, whether it is just the regulator itself or whether something else is affecting it, because as you commented it is related to acceleration, engine load etc. Everyone on here has ignored my posts about it so far so i figure no one really knows and I will just have to do some digging myself. I have a replacement VR to see if that fixes it, just havent had time to put it on yet. At any rate it's far easier to check this first and at least narrow it down to it either being the VR or not, before you go adjusting timing valves etc. Just my 2 cents.

Tue Apr 30, 2013 9:48 am

And I didn't notice the rattle or tick if u will till I was over half way to work and the bug was good and hot about 230 degrees or so

Tue Apr 30, 2013 9:51 am

I will check my VR and I have a timing light and a degree pulley on the car so I believe I set the car at 27 or 28 degrees

Tue Apr 30, 2013 9:51 am

If detonation is the problem then you need to look into it and it's not a big $ prevention. Detonation as the lads mentioned is a serious problem, cos the gas is exploding at the wrong time in the cylinder(s) and basically it is hammering the piston back down against it's upward motion and that causes HUGE stress. So worth checking out and a timing change will fix that. It is nothing more than a adjustment of things in your motor to make them all explode in harmony not against each other.

Tue Apr 30, 2013 10:16 am

If you don't have a timing light yet just mark the spot it is currently set at and then retard (CCW mm at a time) the timing slightly and take it for a drive and listen for the sound it is making and if that sound is disappearing then you know the timing is the issue.

Tue Apr 30, 2013 10:30 am

Onewheeler wrote: And I didn't notice the rattle or tick if u will till I was over half way to work and the bug was good and hot about 230 degrees or so

Improper timing can make the engine run hot. Detonation occurs more readily when the engine is hot.

Tue Apr 30, 2013 11:08 am

Thanks guys for all the advice I will do some working on it when I get home tonight!!!

Wed May 01, 2013 6:25 am

Set the timing at 29 degrees and dropped the idle just a ya and she ran beautiful and smooth through all rpms!!! Also show up to work under the same temp as yesterday weather wise but the motor was 30 degrees cooler!!! Thanks again to everyone's input!!

Wed May 01, 2013 9:47 am

Just to add a note is that the factory timing is great for a straight from the factory engine in 1970 with 1970 gas. Today it is a guide line. You can play with it slightly advance and retard to get the best setting for today. Your indicator is the rattling or pinging of the engine and how it runs.