1.8T Coolant Return Hose Badly Leaking - URGENT PLEASE HELP

**Skezza** · 05-04-2019,01:03 PM

So, I fixed the leak using jubilee clips and having snipped the end off. Great.... although, not quite there yet.

Firstly, while getting the car home, I had the heater on full blast to try and avoid any potential issues with overheating. Part way through, all heat stopped and it is yet to return. I've flushed the system using tap water a few times and as part of that tutorial, you are supposed to turn the heating onto low speed high setting, but no heat ever comes through. I can only assume:
A. Huge air lock?
B. Blocked heater core?

Would a major air lock ever escape? Friend of mine who works in a garage thinks the coolant has to be vacuumed in to Audi's otherwise air locks are inevitable and has offered to do it for free for me, so I might take him up on his offer, but that wouldn't explain the heater core would it?

So I guess I'll have to backflush the heater core at some point? Doesn't look a big job. I assume it's just a case of removing that scuttle panel and connecting up a hose pipe at one end and another hose pipe into a bucket? Perhaps a job for this weekend.

Secondly...... *sigh* I used the thermostat to drain the coolant rather than the screw which is absolutely jammed solid. There's a C clip and O-ring. I flushed it several times without an issue. Then after driving it yesterday for about a mile, the thermostat popped out, losing the O-Ring and leaving the clip in place. No idea what I did wrong. £85 towing home

Should have just taken it a garage

I've ordered a new O-Ring from eBay. I also found one that fits in an assorted kit. Does the O-Ring need to be the correct one or will any O-Ring that fits do the job?

**Crasher** · 05-04-2019,06:15 PM

You mean the temp sender popped out, the "O" ring is N 903 168 02 and that is from memory... I had one of those sensors blow out on me many years ago, I was setting up a G60 Golf and as I unplugged the temp sender to put the ECU in setting mode, the sensor blew out, hit me directly between the eyes and sprayed me all over with boiling coolant. I spent the next four hours in casualty and the next day I had to go to Germany for a show with a bright red scabby scalded face and a square dent between my eyes above my nose from the impact of the flying sensor....

**Skezza** · 08-04-2019,03:28 PM

Originally Posted by Crasher

You mean the temp sender popped out, the "O" ring is N 903 168 02 and that is from memory... I had one of those sensors blow out on me many years ago, I was setting up a G60 Golf and as I unplugged the temp sender to put the ECU in setting mode, the sensor blew out, hit me directly between the eyes and sprayed me all over with boiling coolant. I spent the next four hours in casualty and the next day I had to go to Germany for a show with a bright red scabby scalded face and a square dent between my eyes above my nose from the impact of the flying sensor....

Sorry, the temp sensor/sender that's right. The sensor was hanging down completely loose with the C clip still in place and the O-ring was nowhere to be seen. Unsurprisingly, with no O-ring the header tank coolant drains within about 30 seconds, so really I had no option but to pay for a tow. Pain in the rear end though. That sounds absolutely nasty mind. I did another flush and drain and used the generic O-Ring out of the packet as I'm waiting for the new one to arrive. Not only did the generic O-Ring seal it, the C-clip seemed absolutely solid and didn't want to move at all

Of course that'd be the case when on my drive.

How often do they blow out and does it have anything to do with the clip and O-Ring? Any thoughts on the lack of heat?

**GeorgeE** · 08-04-2019,03:47 PM

Not having had a car with that engine I'll let Crasher respond on how often the blow out.

Lack of heat could be an airlock in the heater matrix/pipework, but it could also be a stuck flap actuator as the motors do give problems. It would be a bit of a co-incidence to happen at the same time, but worth checking. Do you have VCDS to read fault codes?

**Skezza** · 08-04-2019,03:54 PM

Originally Posted by GeorgeE

Not having had a car with that engine I'll let Crasher respond on how often the blow out.

Lack of heat could be an airlock in the heater matrix/pipework, but it could also be a stuck flap actuator as the motors do give problems. It would be a bit of a co-incidence to happen at the same time, but worth checking. Do you have VCDS to read fault codes?

Sure do. I'll give it a scan tonight. Any tips on clearing air locks? I've tried bleeding it with the cap off and then on.... The only thing I've not done really is taken it for a good drive.

**Crasher** · 08-04-2019,08:35 PM

That O ring has been used since 1988 and is very reliable as long as it is installed correctly.

**Skezza** · 09-04-2019,11:16 AM

Originally Posted by Crasher

That O ring has been used since 1988 and is very reliable as long as it is installed correctly.

Interesting. Well the new clips and O rings should be here today, so I can have a proper good look. I assume there's no reason you can't reuse that O-Ring? I did notice on a video online that the lad was pulling quite hard on the sensor and it wasn't popping out.... so clearly I just need to do that before I can be happy that it is safely installed.

Currently the car is still sat on my drive waiting for me to work on it again. I'm still trying to decide whether to backflush the heater matrix just for good measure or perhaps just take it to my mates and getting it vacuum filled and seeing if it helps. I suppose good thing is that with the backflushing, I can do that without loosing all the coolant as i'm connecting the hoses at the top of the system. I think for the time being, I've 'flushed' (using the term loosely considering the air locks) the system with tap water repeatedly and it's now running fairly clear, I'm just going to run some ordinary coolant system flush one last time a perhaps drive it to work so the coolant flush picks up any grime and filth. I'll take some ramps in the back (just in case

) and then drop it as soon as I get home, flush it with de-ionised water..... then finally fill it properly with a nice fresh mix of coolant + de-ionised. I can't keep putting it off but life doesn't half get in the way right?

Lucky I was able to borrow a Passat off my brother in law.

**Crasher** · 09-04-2019,04:29 PM

I did a rad temp sensor on a Golf 5 today and it is the same part, we use Febi sensors normally which come with the O ring and clip but this was a slightly different one and we had to get it genuine so a pulled a clip and O ring off the shelf, we have a lin bin full of both.

**Skezza** · 16-04-2019,01:38 PM

So a bit of good news today. I decided this has gone on long enough and the car needed sorted. Filled with the coolant system flush and tap water, I drove it to work (with a bottle of spare just for topping up). As I got further, I noticed a small amount of warmth through the vents..... by the end of the trip, the warmth was fully back.... so no need to backflush the matrix

I will drop the now probably very dirty tap water, flush with some fresh de-ionised water, flush probably once more for good measure and then finish this job by putting in fresh G12.

Anyone know how many litres the coolant system in the 1.8T is?? I'm surprised how little there is online about it, although one post seems to think 8-10 litres (which isn't as accurate enough imo). Apparently the mix should be somewhere between 30/70 coolant to water and 50/50...... Anything above 30/70 apparently is enough for the UK climate.