[Public-List] A4 overheating

[George Dinwiddie]

Gord,

On 7/12/11 9:12 AM, Gordon Laco wrote:
> Hi gang
>
> Surprise is on day four of a very nice cruise in company with friends
> who sail a Columbia 29.   Their A4 is overheating and we are towing
> them a lot.   It has a new water pump that throws lots of water, and
> the thermostat was already removed... Not much water is coming out
> their exhaust compared to ours
>
> I noticed in the thermostat housing there's lots of rust flakes.  We
> removed them but guess lots more is blocking the cooling jackets.
>
> Is there a way to reverse the water flow in hopes of moving the rust
> flakes?

I know from experience that the water passage in the exhaust manifold 
tends to flake off in pieces big enough to intermittently block the 
outlet. It's very frustrating, because you think you've got it cleared, 
but the next time you use it, it overheats again.

I've found two techniques that help:

I've used a 1/8" tubing on a set of reducers down from a garden hose to 
backflush the cooling passage.  On my manifold, the inlet from the 
engine was a bigger hole than the outlet, so blocking off the outlet and 
putting some fairly-high pressure turbulent water flushed a lot of rust 
flakes back uphill and out the inlet.  Messy, but fun. You could 
probably, in many cases, just pump water into the outlet (with the inlet 
free), but the tubing allowed me to clear out the corners.

Sometimes the flakes are too big to easily move.  Putting a straightened 
coat-hanger or a short length of rigging wire on an electric drill, and 
letting that "whop around" inside the manifold water passage, seems to 
break up the flakes enough that they can be flushed out.

Hope that helps,
   George

P.S. Tell them to sail. I learned to be a much better sailor the summer 
I was first chasing this problem. I had to be.

-- 
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   When I remember bygone days                         George Dinwiddie
   I think how evening follows morn;            gdinwiddie at alberg30.org
   So many I loved were not yet dead,           http://www.Alberg30.org
   So many I love were not yet born.                          also see:
                'The Middle' by Ogden Nash     http://idiacomputing.com
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