Rough sound on cold start

volksfahrer.nl · Posted: Wed May 23, 2012 12:30 pm Post subject: Rough sound on cold start

I've got a 1600 singleport in my bus and it runs great.
It starts quick, pulls good and so on...,
But; On a cold start it sounds rough!

It has s raw sound to it until I step on the gas for a second.
After I reve the engine it runs fine!

On a warm start it doesn't sound like that.

What could it be? I use 20W50 oil btw.
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Campy · Posted: Wed May 23, 2012 1:04 pm Post subject:

I've been using 20/50 Castrol GTX motor oil in my bus engines for almost thirty years. Multi-viscosity oil is good because it is thinner when the engine is cold, when most of the wear is put on an engine, but it does not get thinner when the engine is hot, like regular motor oil.
Regarding the engine running rough, remove the spark plugs and see if they are coated with carbon in order to see if the engine is running rich.
Is the choke valve closing when the engine is cold and moving the cam on the carburetor to raise the idle? Is it opening up all of the way when the engine is warm? The choke can bed adjuisted.
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volksfahrer.nl · Posted: Wed May 23, 2012 1:25 pm Post subject:

I checked the plugs and they look good.
Just a bit brown.
The choke is fine too, it's just a unpleasant rough sound.
Like a bearing is gone! But it disapears once the engine is reved.
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Campy · Posted: Wed May 23, 2012 2:45 pm Post subject:

An engine running at low rpm will make a knocking sound more pronounced. Don't drive the bus until you find out what the problem is, in case there is a defect in the engine.
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mightymouse · Posted: Wed May 23, 2012 4:47 pm Post subject:

The main tunnel is worn out.
This is the #1 symptom. On cold start up it growls and sounds rough until the oil pressure builds. Then the crank is floating and all is good.

20/50 is the worst oil to run in a vw engine. proven time and again.

The front oil piston determines when to direct the oil to the cooler by viscosity.
So when it sees thick oil the piston goes down and bypasses the cooler.
As the oil heats up it thins and the piston is allowed up which forces the oil through the cooler.

With 20/50.... the piston thinks the oil is cold all the time and bypasses the cooler.

BAD IDEA.

You can prob drive it this way for a long time, but i would suggest you tear it down and go through it. Smile

Be better for your case and crank.
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Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

Campy · Posted: Wed May 23, 2012 5:16 pm Post subject:

"As the oil heats up it thins..": A lot of wear is put on an engine when it is running cold. Thicker oil does not lubricate the engine nearly as well when the engine is cold. The thicker oil is still heavier for a time even though it bypasses the oil cooler until it gets thinner. I have been using 20/50 wt. Castro motor oil in my bus engines for almost thirty years and, like a lot of people, with good results.
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mightymouse · Posted: Wed May 23, 2012 5:46 pm Post subject:

"like a lot of people" who either never have their engines for very long, or dont drive them much at all.
This is the norm in the VW community. These are "hobby cars" to most.
I fire mine up EVERY.... EVERY day and drive it. 5+ times a year it gets 2500 mile road trips loaded to the max.

THAT is driving a vw. And proves to you why the factory did what they did.
I build for this type of use because as a kid, an old vw is all i had.

There are many things that people get away with on luck in this family of car folks, but if your building stuff to put your name on, for clients. You have to do things much differently and learn to advise people whats right and whats wrong.
Not what "some guy has been doing for years"

So our views may be a bit diff campy. Im glad youve had good results. Smile

_________________
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.
Thomas Jefferson

Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters.

zozo · Posted: Wed May 23, 2012 5:56 pm Post subject:

EverettB · Posted: Wed May 23, 2012 7:14 pm Post subject:

If you want to debate oil, please use the oil sticky at:
http://www.thesamba.com/vw/forum/viewtopic.php?t=220755

Otherwise, let's stay on topic of his issue please.
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transportertalkman · Samba Member Joined: May 22, 2002 Posts: 319

Grab the crank pulley and pull it back and forth. Sounds like excessive trust bearing play
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