Volkswagen Passat Forum banner

my 1999 passat is gushing coolant out behind the engine/ above the transmission.

4227 Views 39 Replies 8 Participants Last post by  808xN8
how do i find this leak? its a 1.8t. i have coolant temperature sensor out right now. i can't see a bad hose from above or below.seals seem ok on sensor.coolant is clean. so is oil. never overheated before it bursted somewhere while driving. the red cooling system warning light started flashing. upon reaching home, there was a hissing sound of hot air release while coolant gushed down off of transmission to the ground. it was too hot to deal with. i don't want to put CTS back in yet but may have to, to find it. its a tight fit
1 - 20 of 40 Posts
more info

i believe its the gasket on cts gonna put new one in to see if it works.:( taking in and out is a major pain
On the 99 1.8t, it's not all that bad. Try the same job on the newer cars with more plumbing crossing that area!

The CTS fits into a plastic flange (Volkswagen Passat B5 FWD 1.8T Engine Cooling Coolant Flanges - ECS Tuning).
The flange bolts to the back of the head and seals with an o-ring. Two other hoses attach to that flange and seal with o-rings. The CTS and sometimes another blank plug fit into the top of the flange and seal with... you guessed it, o-rings.

You may have a failed o-ring. A cracked or warped flange. A ruptured hose.
Ty. The gasket was fine. The flange was warped. $12 part.
What is this called? It's next to the coolant temperature sensor housing.
The tip cut off is threaded and goes into engine next to housing


See less See more
Nothing cut off. The whole pic came through
when I try to screw it in, it isn't catching. It was covered by a thin metal sheet bolted over it. Is it supposed to screw in or does the metal sheet hold it in? The sheet was nearly torn off from the burst of coolant that came out next/under it
I'm not sure what that part is. It looks like a mount or a sender. Are there any after market gauges in the car? Can you show a picture of where this part lives?
Nothing after market. I removed it to get at cts housing. It's on passenger side nearest air box. Nothing connects to it as far as I know. I'll try to get a picture.
Big hole on left is for flange, hole on right for the part above. :grin:that is a headless bolt in center. I Can't get the rest out. I'm hoping to use hole on bottom right to hold it down with extended piece to flange. I will let you know if it works.


See less See more
If you could look at it straight on, the picture on left is how it sits on engine. Bottom left hole is held down by the broken bolt that also holds flange down.
Sorry, turn picture 90 degrees to the left. The three holes line up right vertically


See less See more
Seems like that area has a bracket for supporting the recirculated crankcase gas (PCV) tube. I'll need to have a closer look at what's under my hood in that area. Do you have a catch can instead of the stock metal tube here?

Use a pair of vice grips to tighten (yes tighten) that stud a little (you'll feel it move when the threads "wake up") before trying to loosen it. If the stuck stud were mine, I'd use a dremel to grind a couple flat spots on opposite sides of that bolt.

If you get things back together this eve, don't forget to use the proper G12++ or G13 coolant...too many things go wrong down the road if you don't.

Good Luck
That looks like a home-made plug for the combi valve port.
Got leak to stop :clap: but temperature gauge on dash in car is not working. Ran car for a little while and doesn't seem to be overheating. Guessing it's the coolant temperature sensor. Light on dash blinks if it or plug on reservoir is not connected.
This is my solution to broken bolt head. I did one up top also for extra support. The plug in middle is held in by the custom pieces above and below. It can't be pulled out by hand. This looks like the plug tip goes into the oil part of head not a coolant tube. It May not have been needed to be unscrewed to get out. The threads are perfect and smooth. I don't think there is some left in there. It spun pretty easy


See less See more
When I took it out. The Reason I took it out is to get at the broken bolt. I was able to get vice grips on it but it was stripping and figured it would break again. Using as a stud to hold it in the proper spot would be better to try first.
I Will be trying the g12 if there is no more leaks. I It Looks like it has had only water for about 10 years. It's a 1999. I bought last year with only 37000 miles on it. I Have learned a lot about sludge and turbos since. Every thing on car is original or warranty work only. Changed to 710n dv and pcv and got oil to stop blowing out oil cap and some turbo lines. Imo on sludge is too much slow/easy driving. Run the turbo hard regularly. It's supposed to be used. Make sure to hit at least 6k rpm. I believe this clears out sludge and if some is sucked through at a high rpm it will grind it through to small pebbles. the first oil filter I changed was the original manufacturers size. Vw changed to larger oil filter to combat sludge issues around 12 years ago. I've
Changed the oil ten times since March, about 11000 miles. It still comes out black with small black pebbles after only 1000 miles. I've used 6+ bottles of sea foam in crank case to help. It Is staying a little cleaner, longer each change. :smiley:my first car was a 1987 gti:smiley: 1.8 engines are great. This sight has been very helpful with old threads covering the issues I've had so far. Could do without the spam to email tho:grin:
That looks like a home-made plug for the combi valve port.

But a 1999 should be an AEB and not have a combi valve. Check to see what three letter code is stamped into the front of the cylinder head. I bet the head was swapped with a different style due to a timing belt failure.
Almost all hose clamps and other connectors are/were all factory placed. I haven't got the feeling it's been worked on like that but it's possible.


See less See more
1 - 20 of 40 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.