Which relief valve piston combo? (Why is my pressure low?)

[TouringBubble]

The sensor is as far down stream as it can be with my setup. I like knowing what's going in to the engine. The stock dummy light switch is in the stock location. You can see it in this image, at the outlet of the thermostat up top. That line goes back to where the cooler would dump back to the engine. https://fbcdn-sphotos-a-a.akamaihd.net/ ... 9817_o.jpg

The sensor I have was a kit with the gauge, so I assume it is the correctly paired version. This is the specific item I have - http://www.egauges.com/vdo_ind.asp?Type ... N=350-1061.

I will look in to a mechanical gauge to test.

[TouringBubble]

... how about something even simpler?

Should I use sealant or Teflon tape on the threads of my sender?
Do not use sealant (including Teflon tape or plumbers pipe dope) on the threads of temperature or pressure senders. This will not allow the sender to properly ground itself to the engine and will cause the temperature to register high and the pressure to register low. This does not include floating ground senders which include a second terminal specifically for grounding.

I have yellow tape on mine. Is it that simple? I'm sure a simple jumper wire to the block would tell the tale ...

[Steve Arndt]

Jumper a ground jumper between the sensor body and ground. That routes the ground around your teflon tape.

There is a lot of "fudge" in VDO gauges. I would say +/- 10 PSI at least. The sending units and gauges aren't accurate or precise.

[TouringBubble]

There is a lot of "fudge" in VDO gauges. I would say +/- 10 PSI at least. The sending units and gauges aren't accurate or precise.

Well I know my temp sender is off, so it makes sense that this one could be off too ... I find that odd though, as they make OEM parts for so many manufacturers ... including VW.

[TouringBubble]

I installed a mechanical gauge in the OE sensor location. It read 5-8 psi higher than the VDO gauge. So, that might be it ...

Jumping the sensor did nothing, so it's grounded well. Ohm check was good a 0.00.

Going to let it cool off then swap in the adjustable plug for the control valve and see if I can bump up pressure just a touch. A couple more PSI would make me feel better about it.

[Steve Arndt]

Sounds great!

[Marc]

Let me see if I've finally got this straight. Your electric VDO sender is located after the cooler loop, which contains ¼" fittings?

[TouringBubble]

Yes.