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Discussion Starter · #1 ·
On my 1.8T recently had "O" ring gasket leak on driver's side of coolant flange at rear of engine. Was on interstate when leak started. Stopped three times to refill system before reaching my destination. Each time engine overheated (temp gauge went to max) before I got refill.

Thinking plastic Coolant Flange was cracked, I replaced it (nasty job) including its gaskets and refilled system venting the air out at the heater connection.

Engine coolant system now works fine, temperature gauge sits in mid-range as it normally did, heater and AC work fine. BUT the dash board exhibits the flashing temperature light and says "STOP" and "see manual". Made sure I re-connected the wires to the two temp sensors and gauge shows normal. Would not be comfortable driving with these warning flashing.

I don't have a code reader device but is this a case of just erasing the overheating problem code from the car's computer ?
 

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I don't have a code reader device but is this a case of just erasing the overheating problem code from the car's computer ?
It may not be as easy as that as a faulty coolant temperature sensor may be triggering the warning. At least replacing the sensor is easier than replacing the flange.
 

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Discussion Starter · #4 ·
Thanks guys. The temp sensor was working ok before the overheating problem, and the dash gauge now reads at the same mid-normal level that it showed before the overheating, so I figured that sensor was okay. But who knows, it could have been "damaged" in some way that triggers the dash warning light. First I'll check the connection under the reservoir to be sure its connected.

So, since no one so far has expressed that a computer code could have been "set" that would cause the dash warning light, I'll assume that's not an issue.
 

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Thanks guys. The temp sensor was working ok before the overheating problem, and the dash gauge now reads at the same mid-normal level that it showed before the overheating, so I figured that sensor was okay. But who knows, it could have been "damaged" in some way that triggers the dash warning light. First I'll check the connection under the reservoir to be sure its connected.

So, since no one so far has expressed that a computer code could have been "set" that would cause the dash warning light, I'll assume that's not an issue.
Google around and you can find ways to get the code without a code reader...or you could go to any auto parts shop and they will read it for you for free usually...or buy a cheapo ten dollar elm327 clone and it will get you by.

the ECTS actually has two sensors in it (I recently learned its not just two outputs, but actually two sensors)...one feeds the dash, and one feeds the ECM....your dash feed may be fine but your feed to the ECM may be shot and thus there could be issues caused by the computer thinking your coolant is much hotter or colder than it is....

and about the coolant reservoir sensor...when I had forgotten to plug mine back in after burping the system, the car lost its shit as soon as i turned it back on with the STOP, SEE MANUAL and temp light.
 

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Discussion Starter · #8 ·
Well you all .... your "easy" fix, the wire harness connection under the reservoir, was the problem .... thank goodness. I forgot to reattach it.

Now my new problem: the coolant pipe connection on the driver's side of the plastic coolant flange keeps dripping. The "o" ring doesn't seem to seal the connection. Took it apart from top-side and carefully reconnected it, to no avail. Bad design: The two bolts holding the connection are not opposite each other thus a "lop-sided connection. Will try adding some Permatex sealant next.
 

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Now my new problem: the coolant pipe connection on the driver's side of the plastic coolant flange keeps dripping. The "o" ring doesn't seem to seal the connection. Took it apart from top-side and carefully reconnected it, to no avail. Bad design: The two bolts holding the connection are not opposite each other thus a "lop-sided connection. Will try adding some Permatex sealant next.
Aftermarket flange? If so, not entirely unexpected - people haven't had good luck with those. I'm dubious sealant will help much.
 

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Sealant will not help, I've been through that with aftermarket flanges. If it's an OEM flange, buy a new seal, loosen the metal coolant pipe and then install the new seal. Tighten the metal coolant pipe bolts last.
 

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The V6 has metal pipes but the O-rings can go bad. I've had both of my son's V6 cars in this year with leaking seals at the temp sensor and the coolant tank. There are several pipes under the intake that can leak, I've replaced those seals on my younger son's car several years ago. I have a writeup in the Info section but no pics. Here is a writeup with pics for the CTS:
V6 Coolant Temperature Sensor Replacement Writeup - PassatB5
 

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yeah CTS was one of the first things done on the adopted b5.5.

I have a not so random misfire on cyl 2 happening after it rains. disappears after a couple minutes. also its like two misfires over that few minutes, but still.
It only happens after it rains.....need to chase that down...again once the truck is fully up and running.
 
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