Years ago I had a similar problem that was finally tracked down to a
leaking rear heater core. Just a thought, the pressure test should
have caught that though.

Jim
On Jul 22, 2006, at 2:26 PM, robert shawn feller wrote:

> after wasting $200 on a new radiator, fan switch and shipping I
> just cannot
> figure out what this damn vans problem is.
>
> Once again here is the info, as I think I'm out of logical ideas.
>
> Replaced coolant temp sensor this winter due to low reading on
> gauge which
> then instantly gave high readings. Readings seemed to get higher as
> spring
> and summer approach even getting LED blink at idle after long ride.
> So today
> we put in the new radiator and have the same issues post install.
>
> here are the facts:
>
>
>   - two temp sender units (yes two new ones from same vendor)
>   - two thermostats
>   - Made resister box to test gauge. Seemed within spec although
> bentley
>   book, online nor VDO have EXACT readings at a given temps. has to
> estimate
>   values from different resources. Here is the data I have from
> compiling
>   different sources:
>   http://carboncow.net/modules/tinycontent/index.php?id=7. Yes those
>   "vague" hot/cold values are given by Vw in their tech manuals,
> how stupid!
>   - Tested senders (2) based on vague data from bentley online,
> appeared
>   to be withing spec
>   - Pulled gauge cluster and tested voltage stabilzer (within bentley
>   spec)
>   - Checked grounds and wiring to sender/gauge and even reterminated
>   connectors or cleaned contacts at both ends
>   - fan speed sender unit operating fine and kicking on when expected.
>   High speed fan is operational but not coming on.
>   - Inferred thermal temp gun shows operating temps within spec on
> hoses
>   and engine block. nothing over 195F...so that explains why fans are
>   operating correctly if you believe the gun.
>
>
> many on the list said the radiator was the next step due to
> restricted flow
> of 20 year old van/radiator. I could understand as severely
> restricted flow
> could give false readings to fan speed sender. then again that
> restricted
> flow would most likely show higher temps at highway speeds.
> Regardless we
> went with a new radiator and fan speed temp sensor. This sender is
> slightly
> lower in temps (from BD) and will kick on the fan a bit earlier. It
> does
> noticeably come on more...which is great. (Please don't bring up
> its bad to
> have lower fan on temps...the thermostat regulates engine temps on
> the low
> side not the radiator.)
>
> If you consider the LED 4 out of 8 on the gauge I am running 6/8 on
> an 80F
> in Ohio driving around town or on the freeway. When I pull into the
> drive
> and let the van idle for 20 minutes after a long drive at 65mph it
> will go
> to 7/8 but the LED is not coming on today. If you read gowesty.com
> page on
> radiators he'd make you think 6/8 or 7/8 are very common while
> Bentley and
> many on this list talk about "dead on" 4/8. Wish I could have done
> this last
> week and tested in 95F degree temps to see if the LED will kick on.
>
> Lastly the old radiator and fan speed sender did have a bit of
> black "oily"
> substance in them. Now since this van had a different engine from
> the PO who
> know what happened with that old one. Before you start saying, "ha!
> you have
> a bad head gasket" add this info to your theory first. No oil in
> water and
> no water in oil. We put a pressure tester on the cooling system and
> its
> holding pressure just fine and there are no bubbles (cavitation)
> from such a
> bad head gasket theory.
>
> Should I just live with this or is there yet something else I can
> check?
>
> --
> shawn feller, ohio
> 1986 vw vanagon gl westfalia
> 1993 vw eurovan gl
> plus a couple of saabs, boats, jet skis, dog and wife (all require
> to much
> maintenance, accept the dog)...
>
> www.carboncow.com
> www.carboncow.net
>