ubiquitouscornknealius

Ello,

I am new to these forums but I have been following them for a while. Today I am here because of a debilitating pressure leak in the cooling system on my allroad. I am going to start from the very beginning and go from there so here goes:

About a week ago, I bought a 2003 allroad quattro 2.7 biturbo automatic from a guy in a really small town in Minnesota. His daughter had spent all her money to buy this car for about 3500 but then it had this cooling issue and I'm sure the mechanic quoted her another 3500 to take the front end off and replace the thermostat/ water pump and she didn't have the money. She bought a cheaper car and moved to the cities, so her father sold the car for really cheap to get out of his driveway. Upon initial observation, the reservoir had already been replaced and the cap was problematic so I figured that's the first thing to try. The coolant looked to be the right colour and I could not see any leaks. There was no coolant in the oil or oil in the coolant. I drove the car, it performed excellently besides overheating at about 15-20 minutes. So I ruled out it being a head gasket issue. I drove it around and I bought it for $900 with the intention of replacing a sticky thermostat and that most likely solving the problem.

After filling out the bill of sale, I drove it about 15 miles up the highway to another small town, Olivia, before it spiked up past the center line. I pulled into a gas station to let it cool. This gas station ended being where we worked on the car for the next few days. We took off the front end/ lock carrier and replaced the thermostat and the timing belt since it probably needed a new TB anyway at its mileage ~165k mi. At this point, we put the whole thing back together and I noticed that I had actually misplaced the little spring-steel U clip for the lower radiator hose. The next day, I picked up a new clip from Napa and put it onto the hose. when I was trying to put the hose back on the radiator, I noticed it was exceptionally difficult. I'm not sure why, but I spent hours trying to get it to click in to no avail and at some point I just decided to call it good (but later found it to not be completely on).

After calling it good, I filled the reservoir with water as the car idled, sealed it, and started on my way towards Minneapolis. The problem was solved at this point. There was no cavitation, and temps maintained normal levels. After about an hour and a half of driving ~70mph the lower radiator hose blew off, the water drained, and the engine temperature spiked. I pulled over to an empty parking lot to let it cool off.

I let it cool for several hours and attempted to actually really get that radiator hose on. After hours and hours of trying to get it on and lubing the o ring and exhausting myself, we finally got it on. Then we filled up the radiator again with water and, thinking the problem was solved as it was before the hose blew off, we got back on the highway... only to find that it was now overheating every ten minutes again. It was raining (so hard to determine a leak) but it did not seem to be leaking. But there were huge air bubbles and cavitation so I think all the water was boiling out the overflow valve as I had to keep refilling it about the amount held in the reservoir after it cooled. I ended up making it to a family friend's house in 10 minute sprints this way after a couple hours.

I did some research, and began to suspect the water pump or the aux pump or perhaps that the new thermostat had exploded when the hose blew off and was now sticking. That night I had some friends to help take the front end off (again) and replace the thermostat (again) along with the water pump and gasket. After getting it all back together, I noticed a slow but substantial leak near the front passenger side of the oil pan. I am almost certain this was due to improperly replacing the thermostat housing the second time, but I knew that this wasn't the real issue because it had only just started and the problem existed the previous day. Once the car was running the leak would stop as the plastic expanded to close the gap, so it was only a very minor leak. after putting it all back together and driving it, I noticed the water temp would spike up and boil after about 20-30 minutes of intensive driving. and the water would be empty at this point and after cooling and refilling, it would drive for about another 10 minutes before overheating again. I was careful to let it roll and park it immediately after it started to overheat every time. We noticed, at this point in time, that water would come out in gushes from apparently underneath the coolant reservoir. after some further research I realised this to be the pressure overflow valve because of air in the system and therefore lower pressure and the water boiling. At this point, I decided to look into the auxilary water pump. This thing seemed utterly superfluous to me. At the very most, you can just let your car idle for 30 seconds after you go crazy on the turbos to the same effect. so after hearing about them leaking all the time, I just replaced mine with a tube. Mine hadn't been leaking but I figured perhaps it had not been spinning at all and holding up the flow.

I drove it around and it was still overheating after about 25 minutes. My friend driving behind me noticed it farting out splashes of water on the interstate which to my understanding is the overflow.

At this point, I had to head back home to Nebraska to get to work, so I left the allroad there and I will be heading back to Minnesota next weekend to continue my quest. My plan now is to take the lock carrier off again and test the thermostat i have in there ( the third one) and then replace the housing/ make sure it is properly torqued on. Then test it again. Also I want to try properly bleeding the heater core. If none of this works, I will take it to somewhere to have it pressure tested and go from there.

Another thing to note is: when I bought it, there was no heat in the cabin of the car at all. At "HI" the air was freezing. After the first replacing of thermostat (when the lower radiator hose was not on properly) I was finally getting heat after about an hour of driving, shortly before the hose blew off and the car overheated. I figured at that point, the new thermostat opened up and let water into the heater core. Then, after replacing the thermostat the second time, along with the water pump, I was getting moderately warm, almost hot, air consistently at "HI." I'm not sure what one can conclude from that information.

Now, planning for heading back up to work on it, I am starting to suspect the radiator is actually clogged and needs to be replaced, but I am not sure, I still strongly doubt it to be the head gasket as there are no other symptoms of that. I know there must be some sort of clog somewhere in the system or somewhere that air is getting in to cause the whole thing. Any suggestions would be very helpful.

Sorry for the long post but I just wanted everyone to have the full picture so that maybe someone would have an idea of how to help. Thank you so much for reading.

amiram

I am not experienced in this engine, but I know that every time the cooling system is empties, after refilling, the air must be drained out from the system!
I hope that you have installed the new thermostat with the air drain hole face up.