[A4] A4 head rebuild, Part 5
igor at s-cars.org
Thu Sep 19 03:23:06 EDT 2002
PART 5 - engine reassembly.
My notes below are NOT meant to be a substitute for not reading your
Bentley! They are only a supplement, ought to share some tricks and
hidden obstacles with you.
36. Clean up the engine block. I usually do it with a brown (coarse)
fibre disk on a high speed drill. First bring the pistons 1 and 4 to
TDC. Clean up the crowns. Then bring the pistons 2 and 3 to TDC. Clean
up the crowns. Scrape the carbon off the tapered tops of cylinders bores
with a razor blade. Be sure not to scratch the cylinder mirror. Spray
the inner cylinder bores with some ZEP antirust/lubricant (I suppose
WD40 will work as well). Wipe everything clean. Turn the crankshaft half
a revolution so that the other two pistons are at the TDC. Wipe
everything clean. Repeat several times until the piston rings stop
bringing the crud up the cylinder mirror. Dry the head bolt bores of any
remaining oil and coolant. BRING THE PISTONS 1 AND 4 BACK TO TDC AND
37. Undo the water pump drain plug and drain the remainder of the
coolant. Undo and remove the water pump and the thermostat housing. Note
the proper orientation of the thermostat. Remove the thermostat. Clean
up the mounting surface for the water pump. Install the new water pump
with a new gasket and the thermostat with a new O-ring. Don't forget to
reinstall the drain plug.
38. Install the new head gasket onto the engine block in proper
orientation. The p/n is facing up. Carefully install the head onto the
block using the two pins in the block as guides. Remember, some valves
are sticking out below the bottom head surface! You don't want to
accidentally bend them or damage the new head gasket. Insert new head
bolts. Torque to the specs and in the sequence outlined in your Bentley.
Button everything up. I will not get into details here.
39. Reinstall the new timing belt with the new tensioner per the
excellent pictorial write-up on Audiworld named "Timing Belt and
Tensioner FAQ" by Andy TN. Remove the spark plugs. Turn the engine
slowly by hand several times, checking the consistency of the timing
marks on the harmonic balancer and the camshaft sprocket. This step has
to be executed perfectly or a disaster may happen when you start the
engine. Reinstall the spark plugs into the head.
40. Prepare the new coolant. I chose the 40% antifreeze + 60% distilled
water solution. Should be good down to -25°C which should be adequate in
my climatic zone. Tested it in my freezer down to -20°C. It didn't
Fill up the system with coolant. As always, while filling up keep
squeezing and releasing the upper radiator hose to help rid the sys of
the air bubbles.
41. Drain the engine oil. Take your time. You really want to evacuate
all that oil contaminated by the carbon crud, dirt, coolant that got
there when you pulled the head.
41. Being a perfectionist I am I filled up the engine with the cheapest
5W30 no-name brand mineral oil that I could find in Wallmart for 97
cents per quart. Its sole purpose in life was to flush the engine and to
be drained once the engine would have reached the operating temperature.
41. Install both new poly-rib belts and their respective tensioners.
(to be continued)
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