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

4221 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
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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.
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?
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.
APH stamped on the head, probably second hand head from a new beetle. AEB in the code on the label at the back of the valve cover. Probably the valve cover that came on this car from the factory. 1999 North American also have the blue square CTS from the factory. What makes you think it's from Europe? Some people/shops like those crimp clamps.
Anything to know about APH head difference than the ARB original?
The APH is like the other 1.8t heads in that it's small port. The AEB head has larger ports. This isn't a huge problem but will probably effect maximum performance somewhat. I'm assuming they kept the stock AEB intake manifold.

Your AEB style intake manifold will have wide ported runners delivering airflow into the head. The head itself will have smaller ports. Where the two parts meet there will be an abrupt size transition. This creates turbulence that impedes airflow.

This is the two sizes back to back for comparison.

The APH head will have a small port and passages machined into the exhaust ports for the SAIP system. This is what the previous mechanic was trying to block closed with those parts. The AEB has no SAIP system and doesn't use that port. They make block-off plates that fit the stock opening and fastener points. You want an air tight seal at that port.
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When unhooking battery my car sometimes will run funny when in gear while stopped, especially reverse. This problem will correct it self in 30-70 miles.
That's probably the ECM getting cleared from lack of power and forgetting learned fuel trims. Without fuel trim correction, it runs a bit rough. Then after a bit of driving, it re-learns how much to correct fueling and begins to run smooth again.

It'd be interesting to see what your trims are (group 32) after a day or so of driving.

Fuel Trim Info - Ross-Tech Wiki
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