Do the blow/suck test on the expansion tank cap - it should be
uni-directional.

If its bi that would be the likely culprit.

On Wed, May 20, 2009 at 8:58 PM, Robert Fisher <refisher@mchsi.com> wrote:

> It was overheating at idle only largely because the tranny was shot and the
> van wasn't rolling; in other words I couldn't make a comparison. I knew the
> radiator fan was working because I remember jumper-testing it and getting
> both speeds, which means it wasn't cycling on its own or I wouldn't have
> bothered. I don't remember if I checked the coolant lines at the time it
> first overheated... I think when I realized it was getting too high I just
> shut it off (the light hadn't come on yet).
>
> I wasn't having an overheating problem before when the van was moving; this
> first came up during one of my start-up and idle sessions when I was
> dealing
> with something else. Before it broke down the needle would commonly sit
> about one needle's width above the led and drop slightly on the road or
> when
> the fan was on.
>
> I swapped in a working used tranny last weekend and bled the system (I had
> already put the new thermostat in for GP). While I was bleeding it the
> needle went back up to the 'normal' position and held there; eventually the
> fan came on. It sounds kind of raspy and anemic to me, but it's moving air.
> It cycled several times and the needle held steady.
>
> Bleeding this thing by the standard method is no fun because one of the POs
> lost the bleeder bolt in the radiator and put a regular bolt in, which
> leads
> to hot coolant spew when I'm trying to do the bleed. I've given some
> thought
> to rigging up a pet-cock type thing but I haven't done it yet. I think at
> this point I'm going to try the tall-pipe method from the Samba.
>
> When I got back from my test drive the needle was still holding steady at
> 'normal'. I turned the van off and opened the hatch. The expansion tank was
> full and there was a little bit of burbling in it (not good, I know). After
> everything had cooled I opened the overflow tank and it was nearly empty,
> so
> I filled it to the mark.
>
> I haven't driven it since (it's non-opped and I'm getting it ready for the
> smog check). Today I was doing some other things and it just occurred to me
> to check the overflow tank (I can't see through it anymore) and coolant
> came
> pouring out- it was basically full. So was the expansion tank.
>
> I remember when I first put this engine back together it took me about
> three
> tries to get it bled properly, so it's entirely possible that's the problem
> now, but I'm puzzled by this overflow bottle filling up. I had the nose up
> for a while, so I suppose it could have just been gravity draining it back,
> but I would've thought the pressure cap would've prevented that. I replaced
> the cap when I put the engine together several years ago, at the same time
> I
> got the other thermostat. I don't have a rig for pressure-testing this
> system so I was thinking I might get another cap and use the old one for a
> pressure tester. I understand that the burbling can be caused by a number
> of
> things ranging from the relatively benign to the catastrophic so I don't
> want to run the thing much.
>
> So I can pressure test the system, do a leak down test and look for
> bubbles,
> bleed it again and so on..., but what's up with the overflow filling up on
> its own? Is the cap bad, or will it just do that from having the nose up,
> or
> did I not let it cool enough before I put more coolant in the overflow?
>
> More thoughts? : )
>
> Thanks,
> Robert
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Dennis Haynes
> Sent: Monday, May 11, 2009 6:11 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Thermostat soup: A comparison.
>
> Does it overheat at idle only? If so then the thermostat is not the
> problem.
> If it was failing it would always over heat, especially at speed. You say
> the radiator fan is working. Does that mean it is cycling on its own? If it
> is turning on by itself that one more indication the t-stat is OK. When the
> fan is running, does the return become noticeably cooler than the feed? The
> radiator may be plugged or an internal baffle is cracked and the coolant is
> not actually flowing through it.
>
> Changing parts until it works is rarely effective. Another possibility is
> that a prior water pump failure damaged the engine case and reduced
> capacity
> at low speed is the result.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Robert Fisher
> Sent: Monday, May 11, 2009 8:15 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Thermostat soup: A comparison.
>
> Stock '87 GL overheats at idle, radiator fan works on both speeds but has
> little/no effect. I got a new thermostat (FLAPS special) and pulled the old
> one. I don't remember what brand the old one is but it was supposed to be a
> good one and it is far beefier in construction; iirc I got it at the local
> import parts place back when but they were closed so I got this new one.
> Old
> one is maybe 7 yrs. old, but does not have a lot of miles/cycles on it.
>
> In boiling water, the new one opens to about 3/8" fairly quickly and also
> closes fairly quickly. The old one opens (to my surprise), but to a little
> less than a 1/4", and takes its sweet time opening and closing. On the one
> hand, I'm thinking I might run the new one for the meantime, get myself
> another 'better' one and swap them out keeping the FLAPS thermostat for a
> spare. On the other hand, the old one didn't really give me much for my
> money. I normally keep a spare around; I don't know what happened to it,
> hence the FLAPS piece.
>
> I know there's widely varying quality in these things, sometimes even
> within
> brands and I've found them dead out of the box, which is why I check them
> (I
> don't recall seeing one that 'partially' worked, however). I've also seen
> ppl argue for strictly OEM thermostats here on the list but I'm a long way
> from any VW dealer.
>
> Thoughts? Recommendations?
>
>
>
> Cya,
>
> Robert
>

--
Jake

1984 Vanagon GL
1986 Westy Weekender "Dixie"

Crescent Beach, BC

www.thebassspa.com
www.crescentbeachguitar.com
http://subyjake.googlepages.com/mydixiedarlin%27