Date:         Mon, 7 Sep 2015 22:18:31 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Replacing Thermostat... and gas mileage
Comments: To: Steve Williams <steve@WILLIAMSITCONSULTING.COM>
In-Reply-To:  <55EE30A3.60104@williamsitconsulting.com>
Content-Type: text/plain; charset="UTF-8"

If the cooling system is tight you should lose very little coolant. Do this with the engine cold and leave the pressure cap in place. There may even be slight vacuum there. It is a good idea to have some new hardware. M6 X 20 X 1.0 and washers. I like to use stainless here. You shouldn’t need to bleed the system after this. 

Make sure you have the correct replacement. Most supplied from an auto parts store will be incorrect. They will have the larger Audi lower disc which will get stuck in the housing both preventing full opening and it will get stuck keeping it from closing. Worse the lower port will be blocked so the t-stat will not be able to act as a mixing valve. You won’t see the problem on the gauge but the system won’t work properly. 

Dennis
 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Steve Williams
Sent: Monday, September 7, 2015 8:50 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Replacing Thermostat... and gas mileage

Hi,

It seems like I need to replace the thermostat on my 1991 2.1 L Westfalia.

It seems straight forward enough, though as Scott pointed out, perhaps there will be a problem getting the plastic housing off.  I can deal with that...

What is the best way to minimize the coolant loss while I'm replacing the thermostat?  I was kind of thinking of putting the back of the van up on ramps to get the housing as high as possible to reduce what would drain from the radiator?  Does this make sense?  or should I just drain the system & start from scratch.

Also, would the engine running "cool" affect the gas mileage?  I know there's a temperature sensor (Temp II?) that feeds the coolant temperature to the ECU, but have no idea what the threshold is, or even what the input to the ECU accomplishes.  I would assume it's kind of like a choke on old carborated engines, but not too sure. It seems like I've been getting poorer fuel economy with the last 4 or 5 tanks & was wondering if there could be a correlation between that & the engine running cooler.

Thanks,
Steve W.