[T3] Thoughts on overheating

[Keith Park]

you may be onto something, senders are notoriously inaccurate and must be
calibrated in boiling water, and there is really only 2 places you want it,
ideally in the sump thru the sump plate but its vulnerable down there OR at
the output of the cooler where the gauge picks up, but you MUST use brass
Tee's and keep them short or youll get a delta Tee across it.  Sump temps
are about 20F hotter than what you'll see at the cooler output and with a
stock engine you want about 200F in the Sump and 180F at the cooler on the
highway on a hot day.  Bigger engines will run hotter, my 1679 runs 20F
hotter under the same conditions than stock.

10psi hot oil pressure off the highway at idle is good with a new motor, and
thats with 30wt.  you dont want too thick an oil on a tight motor as you
wont get as good flow, especially when its cold. the light shouldnt flicker
till 5PSI and thats with a good german sender, so invest in a good german
one and use 30wt or at most 10W40 in the Summer with a tight new motor and
BE SURE TO USE SOMETHING WITH ZDDP in it or add it.

KEith


Topnotch Restorations
topnotch at nycap.rr.com
http://www.a383ina68.addr.com/radiorest/main.htm
71 Squareback  "Hothe"
65 Notchback  "El Baja Rojo"
93 RX7  "Redstur"
87 Golf  "Winterat"
 
-----Original Message-----
From: type3-vwtype3.org [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org]
On Behalf Of Phil Hof
Sent: Wednesday, September 28, 2016 12:29 AM
To: type3-vwtype3.org at lists.vwtype3.org
Subject: Re: [T3] Thoughts on overheating

As many of you know, I have seen overheating (and apparent overheating) of
my '71 Fastback since it was rebuilt  The Invasion journey was trying, but
we made it.  This is with a recently new/rebuilt long block from a trusted
mechanic.

On that trip I had loose points which messed with timing, which caused some
of the overheating and pinging.  But with the ISPwest gauge I had installed
in the full low line indicated I was seeing temps as high as 280-300F.

The points are tight now, and the timing is stable.  It no longer pings.
But the temp gauge still scares me.  I think I have the root cause, though
this may be a bit of wishful thinking.  Here's what I found.

The sending unit is in the line between the galley (right after the pump)
and the filter.  Seeking to protect it from debris, I located it inboard of
the left HE.  But this puts it in the flow of exiting cooling air from the
3-4 head and cylinders.  I hadn't really worried about it, but I think this
is the problem.

I took out my laser/IR thermometer, and found the sump was 220, the oil
cooler was about the same (the bit I could see on top was slightly cooler
but it's hard to be precise and hit the fins, since they are of course
hidden by the tin).  But the sender and nearby fittings were all higher, and
all over the place.

The sender was 240 or so, but the base of it (where the element is located)
was more like 160.  The fitting it screwed into was 280, and the nearby
fitting was 300!.  The filter housing was also about 220 or so.

I now believe these fittings are absorbing the heat from the cooling air,
and that is what I am seeing with my gauge, not oil temperature.  I also
think I need a longer insulating sock on the lines so they do not pick up
heat, too.  I have one on the section near the HE itself, but one in the
stream of cooling air will probably help a little, too.

To move the sender outboard, I need to order more lines and fittings (and
figure some sort of debris shield), so it will take a bit to set it right
(or at least test my theory), but I am breathing again with the likelihood
that there is little or no actual overheating.

220 is a bit high but not unreasonable on a hot day, and with the slightly
larger displacement and higher compression.  It should be manageable with a
good quality oil (now 30wt Valvoline VR1 plus a zinc additive).

Two flies in the ointment.  First, when it is really hot out, and I have
been driving on the freeway, and then I let it sit at idle, I see my
pressure is 10 or even a bit less, triggering my oil light.  This may not
bother some, but it bugs me.  I am thinking of going to a multi-grade VR1
oil so that it doesn't thin out quite so much when hot, maybe a 20-40.  This
may lower initial cold pressure (now at 50-60psi) and increase it when hot.
Second, I am told there is an oil smell when following the car.  I haven't
been able to locate a source, though the bottom of the sump is slightly wet,
as are my six acorn nuts on the plate.  Something to track down, though I
see no apparent leaks to deal with yet.

So my fingers are crossed while I try to find the time to measure for hoses
and fittings from Gene Berg.  But I am breathing a little easier with this
thermometer data.

Any thoughts?
Thanks,
-Phil

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