Leaking water pump MK7 GTI2016

[DSC808]

I'd be curious to hear your story on it

Had a slow leak that became a constant leak. Decided to try Stop Leak. Did not stop it, only slowed it down again.
Ordered new water pump/thermostat from FCP. Installed it and did the same things as you; put everything back together, started up and had a huge leak. It was late and decided to finish the next day. Took everything apart again and adjusted the union. I have a aftermarket intercooler and I have to take apart the front end to get enough space. Drove a few days and I'd still get the low coolant warning. Top up and there was definitely a leak still. One day (5 days or so later) I get the coolant light again. 15 seconds later I get the engine overheat warning. WTF. Never seen that before. Pulled over and a puddle was coming out below. The hose (that connects to the plastic part) that attaches to the front of the water pump somehow came off . I made sure everything was connected the 2nd time around. I don't have a garage, so I just shoved it back on (couldn't get the clip on because I don't have the clearance) and gingerly drove home. Tried getting it on the next day (without taking everything apart). No go. Drove a couple days to work paranoid that it would pop off again and have catastrophic damage. Called up my buddy again and asked to use his garage. Took apart the front end, put hose on and clamped it. Yay. The end.
Nope. Couple days later, coolant light. Top up, next day light again. Found my radiator had a leak; how I don't know. Ordered new radiator from FCP, installed and I still had a bunch of codes. Thermostat, AC would not work with recirculation on, fan would run constantly, etc....
I looked up how StopLeak works and it says that it expands in air. When doing the water pump there was some styrofoam looking bits floating around. I think after I changed the pump there was some Stop Leak in the system, and since I introduced a bunch of air it foamed up internally and gunked up a bunch of sensors. I think maybe thats why the radiator had the tiny leak; maybe it expanded enough between the fins and caused it? Bought Blue Devil Radiator Flush and ran the car with the heat on full blast for about 2 hours. Drained the system and refilled with coolant. All codes gone; AC worked fine. Been about 2 months without any incidents, but I still have 2 gallons of distilled water in the back seat... just in case.....

 

[gdub09]

Okay, so I got it done as DIY - Had to do it twice though.
I did remove the intake manifold to get access to thermostat and pump and left the throttle body on the intake manifold.
I also removed the FAN assembly to get a bit more room to work with. That is a 5 task BTW.

The first time I ended up with a huge leak, most likely because the union which goes to the oil cooler was improperly set... I found this, only at the end, at 11:30 at night. after I put everything together.
Second time taking it apart and putting back on, I did test the cooling circuit by creating a vacuum in the system, before putting intake manifold and all other guts back - just the thermostat and water pump put in place.
I strongly recommend this step which I did not see mentioned somewhere else. BTW - I did use the instructions from the DAP youtube video.

I can say that I can do it again in ~4hrs if I ever have to do it again, but is quite laborious process.
Most of everything is so tight and in the way of something you need access to. Patience and attention are your friend.

Make sure you do not break any electrical connector in the process, as there are a lot you need to touch.

What I would do different next time is to wash with a water hose the engine from all the coolant you will spill in the process of removing hoses/ thermostat. This will allow you to see if coolant leak is fixed or you are observing coolant dripping from the engine block.

I will keep observing mine in the days to come but for now appears there is no leak.

FWIW my OEM thermostat revision was 'H' and the new one purchased from DAP was 'P' Before soon, they will be running out of alphabet letters for Rev # on this part. Whoever designed it wanted a secure job


Good luck!

Glad to hear it went well! Sorry I never responded, rarely do I get on here. I should have mentioned pressure testing after install, sorry about that. That union is what gets most people.

 

[Daks]

Had a slow leak that became a constant leak. Decided to try Stop Leak. Did not stop it, only slowed it down again.
Ordered new water pump/thermostat from FCP. Installed it and did the same things as you; put everything back together, started up and had a huge leak. It was late and decided to finish the next day. Took everything apart again and adjusted the union. I have a aftermarket intercooler and I have to take apart the front end to get enough space. Drove a few days and I'd still get the low coolant warning. Top up and there was definitely a leak still. One day (5 days or so later) I get the coolant light again. 15 seconds later I get the engine overheat warning. WTF. Never seen that before. Pulled over and a puddle was coming out below. The hose (that connects to the plastic part) that attaches to the front of the water pump somehow came off . I made sure everything was connected the 2nd time around. I don't have a garage, so I just shoved it back on (couldn't get the clip on because I don't have the clearance) and gingerly drove home. Tried getting it on the next day (without taking everything apart). No go. Drove a couple days to work paranoid that it would pop off again and have catastrophic damage. Called up my buddy again and asked to use his garage. Took apart the front end, put hose on and clamped it. Yay. The end.
Nope. Couple days later, coolant light. Top up, next day light again. Found my radiator had a leak; how I don't know. Ordered new radiator from FCP, installed and I still had a bunch of codes. Thermostat, AC would not work with recirculation on, fan would run constantly, etc....
I looked up how StopLeak works and it says that it expands in air. When doing the water pump there was some styrofoam looking bits floating around. I think after I changed the pump there was some Stop Leak in the system, and since I introduced a bunch of air it foamed up internally and gunked up a bunch of sensors. I think maybe thats why the radiator had the tiny leak; maybe it expanded enough between the fins and caused it? Bought Blue Devil Radiator Flush and ran the car with the heat on full blast for about 2 hours. Drained the system and refilled with coolant. All codes gone; AC worked fine. Been about 2 months without any incidents, but I still have 2 gallons of distilled water in the back seat... just in case.....

Jesus. Fucking nightmare.