Date: Wed, 14 Sep 2005 23:57:53 -0400
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: WBX oil pressure with/without cooler
In-Reply-To: <6.2.1.2.0.20050913140443.02811260@pop.earthlink.net>
Content-type: text/plain; charset=us-ascii
The oil to water heat exchanger on the 2.1L engines not only helps cool the
oil, but it also warms it up faster. The goal is really to have the oil
temperature follow the coolant temperature. Warming the oil faster helps
improve fuel economy and emissions during the warm up cycle and for short
trip use, helps boil water and condensed fuel out of the oil.
Most of the heat an engine produces is from combustion. In the water boxer,
the majority of this heat is passed to the coolant through the heads and
cylinders. The oil only picks up heat from the splashing of the cylinders
and pistons. Very little is heat is transferred to the oil at the back of
the heads. Thus, depending on load and speed, the oil temp will not follow
the coolant temp. The crankshaft is also a massive heat sink until it gets
warm. At thigh speeds and loads, the oil will get heat from the pistons and
cylinders and create a lot of its own heat from the shear forces in the
bearings and being pumped and splashed about. This is where the WBX can get
into trouble. Enough speed and load can cause to oil temperature to sky
rocket out of control, reducing oil pressure, causing the bearings to heat
up, and then things go south quickly. This can happen with the water
temperature remaining normal. I have seen 270-280F temps. A large
contributor to this problem is having the oil level too high.
12 psi at hot idle is OK. At 4,000 rpm, you should be close to 40 psi with
the oil at 210. The lower limit is 28 psi. I suspect that your rebuild did
not include align boring the case. The bearings are probably loose in the
case and that is why the oil pressure is not where it should be. The rods
can also wear out of round so a good rebuild should include a good
inspection-measuring and having them resized as needed.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Paul Dunham
Sent: Wednesday, September 14, 2005 10:39 PM
To: vanagon@GERRY.VANAGON.COM
Subject: WBX oil pressure with/without cooler
Hello Vanagonites:
This is my first post to this list.
I have a 1984 Westy that I've had for six years or so. It's great, I love
it, blah, blah, blah...
I suspected since I bought it, given the history told in the bag of
receipts that came with it, that the lower end of its stock 1.9 WBX was
probably well worn. It had been given a "top end" job at around 125k, and
it had around 140k on it. It ran strong and I drove it without incident,
but only for a few in-state camping trips with my family.
Last spring I put an oil pressure gauge on it (Volkscafe's excellent kit)
and confirmed my suspicions that the hot idle pressure was dangerously
low. Although the stock sender did not trip to light the idiot light, the
switch in the pressure sender did. So I rebuilt the engine last winter. I
found that the main and rod bearings were worn to a degree that
was nether alarming or surprising, but that the cam bearings were in
terrible shape. Five of the six shells were missing most or all of the top
layer of babbitt, and much of it was laying in the sump as flakes. I've
built a few dozen air cooled VW engines, and have never seen the like. I
suspect that the hydraulic valves are the big difference here, and they
often clattered when the engine was started after sitting a spell.
Anyway, the rebuild came out well, and now it runs like new. I still have
the oil gauge, of course, and am puzzled by range of pressures that I
see. Cold, it's over 50psi. The coolant warms up right away, but the oil
seems to warm up on its own schedule, and doesn't hit a steady state for
around ten minutes or so. I don't have an oil temperature gauge, but
assume an inverse relationship between oil pressure and oil
temperature. Anyway, cruising down the road and fully up to operating
temperature, the pressure is around 30psi, and at idle it drops to around
12psi. I gather that VW skipped the oil
cooler on the 1.9, but added one back on the
2.1 in '86. I have a question for anyone with a 2.1 and an oil pressure
gauge: What is your hot idle oil pressure? At 12psi, mine is double what
it was prior to the rebuild, and I'm not concerned about it, but I am
curious
to know what the guys in Wolfsburg achieved with the water-fed oil cooler
they added in '86.
-Baffled in Bothell
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