Date: Tue, 3 Apr 2007 16:58:52 -0500
Reply-To: John Rodgers <inua@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@CHARTER.NET>
Subject: Re: Coolant loss in expansion tank but not fill tank
In-Reply-To: <BAY138-F31F446889A0C1AB4D84DBBD2670@phx.gbl>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Pam,
For the purposes here, lets call the tank where the coolant level sensor
is the Expansion Tank. The tank where the hose from the cap goes to, and
where you refill it, the "Refill" tank
With the expansion tank full, when the engine warms up, the expanding
ccolant builds pressure in the system and it overflows through the cap,
the hose, and over to the refill tank. The refill tank has three or four
vent holes in the side of the tank towards the rear of the van. You
can't see them unless you pull the tank out. As refill tank fills with
coolant from expansion, the air in the tank vents allowing the tank to
fill unpressurized. If all is well with the cooling system, when the
engine cools, the coolant shrinks, a pressure drops occurs, and
atmospheric pressure pushes through those little vent holes in the
refill tank and pushes the coolant back out of the tank, through the
hose, through the cap and into the expansion tank. If the engine cools
and the coolant does not get pushed back into the expansion tank from
the refill tank, then you will have an expansion tank that is only
partially filled, thus leaving the coolenat level sensor probes exposed,
causing the coolant light on the heater guage to turn on and blink. In
this case you most likely have 1) a bad cap, 2) a bad hose from refill
tank to cap, 3) a leak elsewhere in the system.
The only definitive solution to sleuthing this problem out, is the have
the cooling system pressure tested and have the coolant "sniff" tested
for hydrocarbons from fuel ignition. The latter is to see if you may
have leaking head gaskets allowing the cooling system to be pressurized
by combustion gases. If this is the case - Bad news!! A head job is
required with new gaskets and special attention to getting the things
sealed right with the right sealant. Pitting, corrosion, and eventual
head gasket leakage is a problem with Vanagons.
Thats about it. I'm sure some of the other Volks can weight in here to.
This how I see it.
Good luck,
Regards,
John Rodgers
88 GL Driver
Chelsea, AL
Pam McIntosh wrote:
> Sorry this is so long but it all seems relavant to a 'layperson'
>
> A few weeks ago, upon starting the van at about minus 10 Celcius it
> sounded
> rough. I saw coolant spewing onto the ground (and gas I think from smell)
> from around engine area - no one spot - kind of all around the bottom
> where
> the oil drain plug sits. I turned van off. The coolant level in
> overflow/recovery/refill tank was in normal position (I didn't think to
> check the expansion tank) Oil (15-40) was normal. There was some
> sign of
> wetness looking into engine compartment from inside. What was likely to
> have happened - some seal / gasket shrunk in cold?
>
> I restarted the van and as it didn't even drip I drove it. The red light
> started blinking when the van got up to normal operating temperature (at
> LED) and stayed blinking for the duration of the trip. The radiator fan
> came on as normal (only when lot of slow driving, stop & go etc) The
> temperature did not go above normal (on 100km highway drive or around the
> city). The overflow tank did not go down.
>
> Another cold day the same thing happened. Then, on a warmer day it
> didn't
> spew coolant but red light still blinked when got to operating
> temperature.
>
> I finally consulted the archives and, as a result, checked expansion
> tank -
> it was low. The overflow tank was still at normal position. I didn't
> see
> any crack in expansion tank or sensor and it wasn't dripping from
> there). I
> saw some bubbles on the tank walls. Still no signs of drips on the
> pavement.
>
> I filled the expansion tank right to the very brim of the neck, (it took
> about a liter) recapped it. When I turned the van on, the level in the
> expansion tank went down again. I could see bubbles coming into the
> tank.
> I turned it off, the level came up a bit but not to the brim so I
> refilled
> tank to the brim of the neck then went for a ride.
>
> The light did't come on. Temperature was normal. The fan came on as
> normal.
> The level in the expansion tank again dropped. The level in overflow
> tank
> didn't change. I filled the overflow tank to maximum level when cold
> - is
> this correct or should it be at maximum level when hot?
>
> Again reading through the archives I thought maybe the problem would
> be the
> expansion tank cap so I got a new one - it didn't help. I still loose
> coolant from expansion tank but the fill tank level stays constant. I
> have
> gone through this proceedure (keep filling expansion tank) a few times
> now.
> I'm sure I have air in system - but where is the coolant going? Oil
> looks
> OK but then I'm no mechanic.
>
> I can't see any drips on the pavement. Does it leak out of the engine
> somewhere just when driving and evaporate? What is likely the problem do
> you think? What should I be asking a garage (when I find one) to do
> or look
> for? Should I bother paying to have it bled if there is likely something
> else wrong?
>
> I do have a rear heater that leaks when the heater is off only - yes
> off -
> not on. The heater has been on for about a year and not leaking (-see
> separate posting "' 91 rear heater leak only when heater 'off' "). I
> have
> read in archives that air can get into system from rear heater but
> wonder if
> this is the problem but think it is likely from what happened in the
> cold?
>
> Thanks for any advise - I feel bad that I get so much info form
> Vanagon List
> but can not offer anything
>
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