Date: Mon, 17 Dec 2007 07:31:49 -0800
Reply-To: Michael Diehr <md03@XOCHI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Diehr <md03@XOCHI.COM>
Subject: Re: Knock Knock ?
In-Reply-To: <00b001c83eb1$ab8a4c00$6401a8c0@TOSHIBALAP>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
Thanks for all the Sherlock Homes who replied with theories.
Update: the mechanic says the timing was off and the motor was
running lean, and that it's been adjusted and is running much better
now. He also noted that the PM (previous mechanic) didn't put
gaskets on the exhaust headers. He also said he'd not been able to
hear the knock/ping/tap noise, which is not surprising since I
couldn't hear it either on the drive into the shop. (Don't we love
our vanagons?!!?!)
I've not yet driven it yet, but it sounds like with luck that it's not
anything terrible like reversed pistons or broken rings.
I guess it's not clear how much damage I may have done by running lean
for many hundred miles, but I was aware of the issue and was trying to
baby it...
Rocket J Squirrel: this perhaps explains some of our MPG
differences? A dangerously-lean condition on my engine giving me
18MPG. I guess there's no free lunch...
On Dec 14, 2007, at 4:30 PM, Scott Daniel - Shazam wrote:
> Bingo on the small exhaust leak !
> A small one can sound like a tick tick tick sound all right,
> And waterboxer exhaust pipes like to warp, contributing to gasket
> leak,
> and the pipes crack sometimes too.
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of
> Dennis Haynes
> Sent: Friday, December 14, 2007 3:27 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Knock Knock ?
>
> A tick tick sound under load could be something as simple as and
> exhaust
> gasket leak or more complicated as piston slap or even a broken
> ring. A
> compression or leak down test may be able to locate the offending
> ring.
> Piston slap would more likely be due to a piston installed backward
> or a
> size tolerance problem between the cylinder and piston. A bad wrist
> pin
> bushing can also cause noises but that like a rod bearing is usually
> as
> load is reduced.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of
> Michael Diehr
> Sent: Friday, December 14, 2007 11:02 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Knock Knock ?
>
> Stump the chumps: I've got an 85 auto with a rebuilt engine with
> about 5000 miles on it. It's running ok overall (mpg around 17-18 in
> fast california driving), but power seems a bit off (even for vanagon
> standards).
>
> The problem: The engine makes a ticktick sound at around 3000 rpm
> that was definitely not there in the prior engine.
>
> It sounds a bit like ping, but the behavior is not always ping-like:
> * only happens under 1/2 to full throttle under load
> (consistent with ping)
> * it's worse at altitude and cold
> (backwards? ping is usually worse at sea level on hot days, right?)
> * not obviously connected to the octane of fuel.
> (inconsistent with ping)
> * the frequency of the tick noise sounds like it may be happening on
> 1 cylinder only
> (e.g. unlike ping, it doesn't seem to decrease in frequency when
> you add more
> throttle, just the loudness increases. When i've driven cars
> with ping,
> usually the ping frequency is dependent on throttle/load too)
>
> It has rebuilt injectors that were flow tested at witchhunter. The
> valves have never been adjusted, and I *think* the shop that installed
> the engine (to which i'm unable/unwilling to go back to them...a long
> story) may have replaced the distributor and messed with the mixture
> adjustment screw, as well as putting in a new (rebuilt) ECU. I'm
> running mobil 1 15/50 w/mahle filter.
>
> Ideas? I'm having a real mechanic look at it, and would like to make
> sensible suggestions...
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