The bypass valve on the thermostat housing is off, fully clockwise.

I see I have a new thermostat housing, plastic, 025 112 114.

I have a spare thermostat Behr 025 121 113F. It has 2 o- rings in the box. I’ve probably had this part for 10 yrs or more, any reason I shouldn’t install it today?

-Mark

Sent from my iPhone

> On Jan 22, 2022, at 9:28 AM, Mark McCulley <markmcculley@gmail.com> wrote:
> 
> 
> That wouldn’t explain why one coolant pipe was cold when I stopped would it?  The gauge didn’t just instantly change, it was gradual, but fairly quick.
> 
> I think I have a spare thermostat with me, I may install it today. Don’t have a full set of tools, but I have 10 and 13mm  spanners and I think that’s all I need. 
> 
> I neglected to mention this is a syncro, if that matters. 
> 
> Original oil cooler is still present, no mods there.
> 
> Thanks for your assistance Dennis.
> 
> -Mark
> 
>> On Sat, Jan 22, 2022 at 6:34 AM Dennis Haynes <d23haynes57@hotmail.com> wrote:
>> Is it possible that you have a gauge-connection problem? If the engine was really going cold it would seem the oil temp would also drop especially if still using the original oil to coolant heat exchanger. 
>> 
>> Dennis
>> 
>> -----Original Message-----
>> From: Vanagon Mailing List <vanagon@gerry.vanagon.com> On Behalf Of Mark McCulley
>> Sent: Friday, January 21, 2022 10:36 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: On road, Having problem, coolant related
>> 
>> I don’t know specifics on the thermostat but it was installed by a shop that specializes in Vanagons.  I will ask them when I take it back for repair.
>> 
>> We continued to destination, temp gauge was all over the place though never too hot. I could not correlate with anything including turning front heat on and off. Oil temp stayed steady at around 200F. Ambient air temp was 45F not very cold. I will check the bypass valve tomorrow.
>> 
>> Thanks,
>> Mark
>> 
>> On Fri, Jan 21, 2022 at 4:42 PM Dennis Haynes <d23haynes57@hotmail.com>
>> wrote:
>> 
>> > As the Vanagon has such a massively, oversized cooling system along 
>> > with an extremely large heater core, getting hit with cold outside 
>> > air, keeping the engine up to temperature can be a challenge during very cold weather.
>> > VW became aware of this early on and the fix was the series "F" thermostat.
>> > This stat features a delayed but fast acting response to temp and the 
>> > disc that seals the is further gasketed to prevent any bypass while 
>> > closed. So do you have the correct t-stat? Further, for the correct 
>> > stat if not of the Vanagon specific design, the lower disc can be too 
>> > large diameter and cause the stat to wedge and get stuck open. Also, 
>> > as the bypass will close too early from this excessive cooling will 
>> > also result from the lack of mixing the hot coolant leaving the engine 
>> > with the cold coolant coming from the radiator. The thermostat set up 
>> > is really a mixing valve and part of the goal is for the coolant to 
>> > always be flowing through the engine keeping the heads and case at the same temperature.
>> >
>> > Next, on top of the thermostat is that small hose and bypass valve. 
>> > Make sure that valve is closed.
>> >
>> > Try closing the heater valve to see if that brings the temp up some 
>> > and next step is block off part of the radiator.
>> >
>> > Dennis
>> >
>> >
>> > -----Original Message-----
>> > From: Vanagon Mailing List <vanagon@gerry.vanagon.com> On Behalf Of 
>> > Mark McCulley
>> > Sent: Friday, January 21, 2022 3:18 PM
>> > To: vanagon@GERRY.VANAGON.COM
>> > Subject: Re: On road, Having problem, coolant related
>> >
>> > Thanks Ken. Not optimal, I know but is it safe to continue? Loaded up 
>> > for
>> > 2 days camping with wife and dogs. 75 miles to destination, 40 to get home.
>> >
>> > Sent from my iPhone
>> >
>> > > On Jan 21, 2022, at 12:11 PM, kenneth wilford <kenwilfy@gmail.com>
>> > wrote:
>> > >
>> > > 
>> > > Sounds like thermostat has failed open.
>> > >
>> > > Ken
>> > >
>> > >> On Fri, Jan 21, 2022, 3:04 PM Mark McCulley 
>> > >> <markmcculley@gmail.com>
>> > wrote:
>> > >> This is a weird one.
>> > >>
>> > >> Coolant gauge started going LOWER while driving at 65mph for 30 min.
>> > Pulled over to check it out, by then gauge was like it was a cold engine.
>> > >>
>> > >> -GW expansion tank is full.
>> > >> -One of the 2 hoses from engine to radiator is cold.
>> > >> -Radiator is cold.
>> > >> -No coolant leaking.
>> > >> -Oil looks good
>> > >> -I opened bleed screw on radiator and no air, just coolant.
>> > >>
>> > >> After stopping 10 minutes I started van and temp came up to normal 
>> > >> and
>> > radiator got hot. Then a get running a few minutes the temp gauge went 
>> > back down.
>> > >>
>> > >> I recently had the entire cooling system renewed, new everything.
>> > >>
>> > >> I have the rear heater core out and both hoses are plugged
>> > >>
>> > >> Ideas?
>> > >>
>> > >> -Mark
>> > >> 87 Westy
>> > >>
>> > >>
>> > >>
>> > >> Sent from my iPhone
>> >