View Full Version : Name That Coolant Part

02-21-2014, 04:20 PM
Hey all,

Had a bad coolant leak on and off the past few days and finally figured out where it was coming from. Seems like a weird place to leak. Anyone with this problem know what the part number is by any chance? It looks like a small elbow but I am not sure where it connects to. Held on by a clip. TIA

02-21-2014, 07:35 PM
Is that the thermostat housing on a 1.8 ?

02-21-2014, 08:06 PM
yea that's the thermostat housing.

02-21-2014, 08:07 PM
That is indeed the lower radiator hose connection to the plastic thermostat housing (water neck) on a 2001 1.8T AWM engine. Not a surprising place for a leak at all. I can't tell from the photo, but the problem could be any of the following:

- t-stat o-ring failure
- t-stat plastic housing failure (cracked or distorted)
- lower rad hose o-ring failure
- lower rad hose quick-connect fitting failure (cracked or distorted)

Those are basically in order of most likely to least likely. If I was going in to tackle this problem, I'd probably have these items in hand before starting:
- new BEHR brand t-stat
- new t-stat o-ring
- new OEM t-stat housing

If leak persists, then replace lower radiator hose assembly.

02-21-2014, 11:01 PM
Thanks everyone a ton for the useful information. Sorry the pic may be kind of unclear. It is looking top down below the alternator. Can also be seen between the first gap of the IM. By thermostat do you mean where the coolant temp sensor goes into? For some reason I thought that was behind the engine under the combi valve, probably mixing something up here. It looked like it was leaking where the plastic elbow connects to the hose going into the engine(?) not the one going to the radiator.

Almost seems like it stopped itself from leaking, it left some sticky and dried pink white substance the path is was dripping (White dried stuff in the pic). Can't find this part on ECS or any searches for lower radiator assembly. I cant see this (http://www.ecstuning.com/Audi-B5_A4-FWD-1.8T/Search/SiteSearch/Thermostat/ES2581870/), just that elbow and where the radiator hose connects to the radiator.

I'll have to look into the t stat. Hope it's not bad or anything. Walky thanks again. I am guessing a bad O ring, I hate how whenever I take my car to the shop something happens a few days after. I don't want to resort to using a coolant leak additive lol.

02-21-2014, 11:07 PM
The t-stat being bad is different from the housing being bad. If the t-stat is bad you may overheat depending if its stuck open or closed. I believe the housing may be cracked. The housing is very cheap to replace, should be like 12 bucks. Replace the thermostat and housing at the same time! btw this is what the thermostat looks like.


02-22-2014, 10:27 PM
Thank man, yeah I finally got around to poking around the engine and that elbow connects the lower radiator hose to the thermostat housing (long hard plastic pipe). Going to see if I can access the housing from under the car, looks like a rather inconvenient location. Not overheating at all, no indicative signs of a stuck thermostat. Well no leaks so far, perhaps it plugged the crack when the coolant dried.

02-22-2014, 10:34 PM
To get one of the housing bolts off you'll have to use a long extension/swivel to get past the alternator, or remove you can remove the alternator (good luck getting it back on.)

02-22-2014, 10:34 PM
You can access the housing with a long extension bar with a 10mm socket from the top looking between the alternator and throttle body.

02-22-2014, 10:45 PM
Screw taking off the alternator, that thing is a bitch lol. The bad part is the pulley fan. I just wish I could see exactly where it was leaking from. Can't see how the housing would become cracked out of nowhere. But the t stat housing doesn't seem complicated, its literally just a tube with a sensor screwed into it. No need to drain coolant I assume, just clamp the hose. Added on the future todo list unless it gets really bad.

02-22-2014, 10:47 PM
you dont need to take off the alternator. Just get the angle right theres only 2 10m bolt holding it on. when u take off the housing a lot of coolant is gonna come out

02-23-2014, 08:58 AM
The t stat housing uses a 10mm socket or 5mm hex. Whole bunch of other sh*t removed when I was doing rather intensive work, but you get the idea.


02-23-2014, 10:59 AM
*Money Shot*

That's great, Mitch. Pure drugs.

Can't see how the housing would become cracked out of nowhere.

So it isn't allowed to just crack? It has to have a reason? I'll give you some: it's made of plastic. It's 15 years old. It has scorching hot coolant going through it at all times. Did I mention it's made of plastic?

02-23-2014, 12:47 PM
So it isn't allowed to just crack? It has to have a reason? I'll give you some: it's made of plastic. It's 15 years old. It has scorching hot coolant going through it at all times. Did I mention it's made of plastic?

Of course, I should have known better lol Audi never thought about designing our cars to last more than 10 years. But hey at least the thermostat is still working. Wish I had the awesome power vacuum bleeder my mechanic just used to put in new G12.
Seerlah THANK YOU for the pic [up][up] I've been hunting for such a picture all last night. Also good thing I just bought a set of universal joints.

02-23-2014, 01:04 PM
haha that was the same pic Mitch sent me, totally forgot about that! Helped me so much too. Mr.Mitch saves the day again