GM water pump

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In a message dated 98-10-12 19:07:43 EDT, you write:

<< Subj:	 Re: GM water pump
 Date:	98-10-12 19:07:43 EDT
 From:	marquise at candw.lc (Martin Powlette)
 Sender:	owner-diy_efi at efi332.eng.ohio-state.edu
 Reply-to:	diy_efi at efi332.eng.ohio-state.edu
 To:	diy_efi at efi332.eng.ohio-state.edu
 
 I have copied a mail I just sent to 2 of the other guys
 Thanks for your reply Todd & Joe. The engine does carry a serpentine belt and
 auto tensioner.  The fan clutch and hub are all brand new because there was a
 slight wobble from the last pump.  The engine does have antifreeze and the
fan
 looks ok, revets and all.  The correct pump issue is one I will have to
double
 check but I would hate to think that even with the Vin # the dealer is giving
me
 the wrong pump not once but three times.  Foreign matter maybe but to destroy
a
 seal in first one week and the last 2 days why???
 You must be and if you are familiar with the intake gaskets for theV8 5.7L
 engine it reads this side up and there is a tin strip that is suppose to fit
 over the rear coolant passages.  What if, just what if it is placed on the
front
 passages instead ??.(intake was taken off by another mechanic once) Seeing
that
 a water pump is a positive displacement pump more rpm more pressure if the
 coolant passage is blocked at the manifold and the pressure creates a build
up
 the seal  maybe the the point of least resistance and leak.  I am just trying
 interlectual speculation if there is such a thing.  The vehicle is no more
than
 5years, How much foreign matter can be in there unless it was deliberate???
Joe
 added the heater element...  the heater core was leaking now bypassed and
simply
 routed right back into the manifold, so from the rad and into the
 manifold...point, point ! Joe but When an engine is overheating the cap
releases
 the pressure long before any seal, so shouldn't the cap blow the presssure
 before the seal in the pump if it is a pressure issue.  Check what is the
 closest point to the waterpump outlet and if it is the coolant passage going
 into the manifold maybe, just maybe the gasket issue.
 Thanks for your time Todd and Joe  Keep in touch and give me your thoughts I
am
 lost for ideas myself.
 
 Martin
 
 Hi Martin,
      It seems I remember chev's having a bypass underneath the thermostat to
bypass water back to the water pump while the thermostat is closed and as this
passage gets old and crusty with rust, block pressure rises with rpm and
pushes past the seal in the water pump,,,,and yes you are correct there is a
plate in the intake gasket that is supposed to be in the rear of the
engine,,,,,an easy way to check for this is to remove the thermostat housing
and unbend a coat hanger(DIY lol) through the passage to see if the plate is
in the front by accident....p.s. I have seen many marine engines at over 30lbs
block pressure and not push past the water pump seal....but over 50 it is
inevitable....keep in mind block pressure does not necessarily mean radiator
pressure.....and if checking block pressure you have to check both sides of
the block as it does not equalize until it joins at the thermostat....hth's
-Carl Summers