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Discussion Starter · #1 ·
So I'm working on a 2001 Passat 1.8T and when changing the thermostat I stumbled into the mystery below. The entire "thermostat" part of the thermostat is missing and I can't figure out where it is. It didn't come out with the outer frame and o-ring, so I'm wondering if it is stuck in the block on the left side of the opening. When I reach in there I can feel something, and I took a mirror and could see what looks like round black/brass rings.

Could really use some help on this one before I start bending wire and pulling on things. A couple of questions:
  • Should there be anything to the left of the opening, or would it normally be open space?
  • Has anyone run into this before, and if so any tricks for pulling out the damaged piece?
From what I can tell there isn't anywhere else the broken piece could have gone. The outer frame was blocking the flow down, and the other branches are too small. Photos below of the new thermostat and what I pulled out of the car.

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Discussion Starter · #2 ·
One other follow-up on this one - when I started work on the car the heater core was bypassed, so I reconnected it and it was leaking (suspected that was the reason for the bypass). Any chance the person who did the bypass would have deliberately cut down the thermostat and left it the way I found it?
 

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The water pump impeller is to the left of the thermostat.
Yes, it's possible that it could be on purpose, especially with all of the sealant they smeared on there. That looks like it was cut on purpose.
 
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If that wasn't you that cut it up trying to take it out, I'd definitely say that looks intentional.
So now the question begs, they probably had an over heating issue (otherwise why the hackery).
Why wouldn't you just remove the thermostat all together? Seems the much easier route to me.
 
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Could be someone had the false notion that butchering the thermostat would be good for the engine (runs cooler, better for the engine the thinking goes). Actually that will lead to sludge due to the coolant not reaching running temp quickly, or even ever, poor fuel economy due to the ECU staying in rich warm-up mode too long, and finally heat wasted into the coolant due to the too-cold cylinder walls.
 

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Discussion Starter · #6 ·
As always very much appreciate the support and the fast responses. Really a great community. Will keep you posted on what I find. I did a full flush of the system and reloaded it with Pentofrost. If the previous ratio was off that will be fixed now. Replaced the thermostat and o-ring. Previously I tried some of the liquid aluminum for the heater core leak, and it seemed to work, so that is good. I have a replacement heater core but will hold off on the fun of pulling the dash in the near term.

The initial check was showing the temperature gauge pegged right in the center, which is where my other Passat (2002 1.8T wagon) has been since we bought it. Not sure if it matters but this 2001 Passat had the smaller oil filter, and I switched that up to the bigger size when I changed the oil.

Never dull with this stuff. Can't imagine the crazy stuff you serious mechanics find, plus all the BS you get about what was actually done on cars.

Graham
 

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It's crazy that some shops and auto parts stores still show the smaller filter as recommended for that engine. I think the switch by VW was about 20 years ago.
 
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