No, they are most likely not related.  I just had a customer's van here
that did the same thing.  It was the motor mounts.  You should check your
transmission mount as well.

I would check and fix that coolant leak as soon as possible as well though.

Ken Wilford
John 3:16
www.vanagain.com

On Thu, Mar 27, 2014 at 8:01 AM, Steven Shelton <shelton4@gmail.com> wrote:

> Lately, about 1/3 to 1/2 the time i start my 1985 1.9L, I hear and feel a
> loud THUNK! from the rear.  It runs OK after the thunk.  I thought it was
> most likely motor mount(s), but yesterday i was looking under the van and
> saw a wet spot from coolant dripping from somewhere on the driver's side of
> the engine.  Last night I came up with the unpleasant theory that the  two
> could be related; the coolant could be leaking into the cylinder as well as
> outside, and the thunk could be momentary hydro-lock.  Is this a
> possibility?  It's a VW rebuilt engine wit 54,000 miles on it.
>

--
Thanks,
Ken Wilford
John 3:16
www.vanagain.com