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Post by busaddict on Oct 23, 2014 10:08:38 GMT -8
The engine starts and idles just fine, but when under a load, especially in 3rd, I hear a loud clattering valve sound. At least I think it's the valves. I adjusted the valves this summer, exhaust valves were tight, especially number 3. We did several trips up island and only began to notice the valve noise on the last one. Both heads were replaced by the PO just over 10 years ago. Any ideas or suggestions? Do you have to remove the engine to replace the heads? The bus is parked for winter now, but I'll have to deal with this in the spring. It looks discoloured under the left side valve cover.  |
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Post by Volktales on Oct 24, 2014 19:32:52 GMT -8
Are the valve clearances still OK? You were not hearing "pinging" under load instead were you??? I can't say I have heard valve noise under load....
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Post by busaddict on Oct 24, 2014 21:25:38 GMT -8
Russ, I checked the valves 3 times this summer. 1st time before the trip to Tofino the exhaust valves were noticeably tight. The bus is off the road now, but when the sun comes out I will check again. If they were too loose would it cause pinging? Thanks...
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Post by Volktales on Oct 24, 2014 21:36:46 GMT -8
Pinging refers to a noise you here under load conditions and is also known as spark knock. Basically it is due to fuel not burning properly in the cylinder under load. The most common causes of this are hot running, over advanced timing, lean mixture, poor quality gas. Try some premium fuel and if the noise is gone, then at least you know were to look. Valve clearances are not related to pinging unless too tight causing overheating issues...
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Post by busaddict on Oct 25, 2014 0:09:09 GMT -8
I've been using Chevron 94 octane. The timing had been at 32 BTDC (hose off) on my Mexican Bosch SVDA. Just to be sure I backed it off to 30 with little or no change.
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Post by busaddict on Oct 27, 2014 19:01:02 GMT -8
So I ran the engine in the driveway while I cleaned up the bus for storage and it sounded fine. Couldn't hear anything mechanically wrong. Perhaps the valves are adjusted improperly. Is it spring yet?  |
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Post by busaddict on Nov 1, 2014 20:30:09 GMT -8
Was reading on the Samba about possible issues and the subject of vacuum leaks came up. This could be it, the engine runs well at low revs and only makes a noise when revving under load. I had changed the distributor not long before this came up, but it's a fairly new Mexican Bosch SVDA. Before that was a nice vintage bus SVDA I got from HighTopRob, maybe I should have left it alone as it was working fine.
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Post by Volktales on Nov 1, 2014 20:39:15 GMT -8
Lots of comments on the Samba about crappy quality distributors out there...
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Post by busaddict on Nov 1, 2014 20:53:04 GMT -8
Funny, they're so simple you'd think that wouldn't be the case. The Mexican Bosch I have run many times before, but you never know. I'm wondering if I've developed a small vacuum leak somewhere. The bus is in storage now, waiting for a sunny day to work on it again. This reminds me of a similar issue I had with my '73 bus. It was running really erratically, timing all over the place, the mechanic I took it to said he thought it might be something mechanical and basically sent me home with a bill and a van that was running very badly. That was my cue to get out the books and do some homework. I suspected the distributor, to prove my point I installed a 009 and the bus ran great! I talked about this in more detail on the old forum. I always tell myself to keep better notes on my VWs, but I usually end up re-reading my forum posts.
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