Date:         Thu, 8 Apr 2004 12:40:31 EDT
Reply-To:     Oxroad@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jeff Oxroad <Oxroad@AOL.COM>
Subject:      Re: Rad Fan isn't working properly
Comments: To: eunrau@YAHOO.CA
Content-Type: text/plain; charset="US-ASCII"

In a message dated 4/7/2004 9:11:22 PM Pacific Daylight Time, eunrau@YAHOO.CA
writes:


> My rad fan used to kick in when the needle reached 1/2
> of a needle width away from the LED; now it isn't
> turning on at all - at least at the temps that I have
> allow the engine to reach.
>
>

Here's what was up with mine. The fan was coming on "late." That is to say
the needle would get up above the LED in some cases and then finally the fan
would come on. This would happen especially when I got off the highway and then
was waiting at a stop light. The temp gauge needle usually lived right in the
middle of the LED. Then like I said off the highway it would rise pretty
quickly when the bus was stopped at a light.

Also in stop and go traffic the needle would rise "too high" before the fan
finally came on. Then it would finally come on the high speed. On long climbs
like over the Continental Divide in CO the bus would run quite hot even once
the fan came on.

I replaced the radiator and solved the problem. Here's what I saw in the old
radiator. First it was copper where the replacement was aluminum. Second the
radiator had a restricted water flow inside due to build up of white deposits
inside--I'm assuming lime or minerals or whatever was in the water that had
been in there for the last 17 years, at that time.

I cut up the old radiator to dispose of it and teach it a lesson. I saw the
top and bottom of the radiator are separate chambers. This means the hot fluid
from the engine fills up the coils in the top chamber first then fills up the
bottom chamber coils. The radiator fan switch was int he bottom chamber. So I
figure with the restricted flow in the radiator due to build up the hot fluid
was taking a while to get to the fan switch. The temp guage sensor is in the
engine block--or rather thermostat housing. So lets say you have an 87 degee
celcius thermostat which is stock. The thermostat opens at 87 lets say for
arguements sake. The 87 degree coolant has a long route to the radiator--then the
trip to the fan switch is longer and is slowed by the build up in the radiator.
Plus the old fan switch is 'insulated" by the crud and build up on its sensor
in the raditor. So the hot liquid takes it time getting to the bottom half of
the radiator.

Now the fan kicks on it's low speed at 93 degrees according to my Bentley
manual. I think the temperatures change very rapidly in the cooling system. So
you gauge at the engine is rising while the fluid in the radiator is slowly
getting to the lower chamber of the radiator and eventually reaching the fan
switch which then has to heat up to 93. In my opinion this is leading to an over
heating situation. And in my case under hard conditions--heavy traffic, but more
with long hill climbs, I did overheat.

A new radiator and switch solved the problem.

That is my experience and not necessarily your problem. I had the old style
copper radiator as I said and I'm guessing the DPO used tap water. With the new
engine and radiator I only use distilled water and VW coolant mix.

Having said all that if your water pump isn't getting the hot coolant to the
radiator because it needs replacement it seems your symptoms would be similar.
Also a stickly or malfunctioning thermostat could be the problem. But that
doesn;t explain why the fan comes on later. Unless of course someone installed
tha "cooler" fan swith somewhere in the buses life to compensate for one of
these problems, most likely a poorly functioning radiator. Check the part number
on the switch you took out . I believe the stock switch is part number 321 959
481D while the "cooler" switch is 321 959 481 D8.

I hope some of this makes sense.
Best
Jeff
83 Westfalia
LA,CA