Author Topic: B6 A4 1.8t cylinder 2 misfires, rough cold starts, coolant in cylinder  (Read 4723 times)

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Jeff@PGP

  • Posts: 65
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I just finished a head gasket job that turned into a head replacement job for a customer's 2003 A4 1.8t AMB code motor today.
He complained about really rough cold starts and burning coolant, random #2 misfires, coolant loss with no evidence of external leaks.We suspected a bad head gasket, and the coolant loss was confirmed after I pulled #2 plug first thing in the morning to find 1/4" of coolant in the cylinder through the spark plug hole.

I proceeded to remove the head, all the while thinking of a similar job I did for a customer 3 years ago with the same year/make/model and same symptoms. That customer's issue turned out to be a pinhole leak in the aluminum head casting of cylinder #2, just next to #1 intake valve's guide, which dripped coolant into the combustion chamber over night and misted coolant while running, causing misses and rough starts.

To my surprise, I found a stain of coolant in the exact same spot, and burnt/ caked coolant on the stem and fillet right up to the seat on cylinder 2 intake valve #1. Thinking this is more than coincidence, I searched for others with the same problem and it seems as though the AMB motors have a bad batch of heads that either crack over time or have thin walls to the water jackets around #2 causing this hard to diagnose problem.

In both cases, I replaced the heads with VW 1.8t heads and so far, so good.

jeff.


Autohau5

  • Posts: 6773
  • Gasoline rainbow in the gutter
Ford 4.0L SOHC heads have pretty much the same issue. It can be difficult to spot as it's not something you'd normally look for.
'01 A6 2.7TT 6MT  |  '81 Rabbit S 16VG60   |  '15 Touareg TDI R-Line   |   '96 YZF750R

sanjose*

  • Posts: 31
I just finished a head gasket job that turned into a head replacement job for a customer's 2003 A4 1.8t AMB code motor today.
He complained about really rough cold starts and burning coolant, random #2 misfires, coolant loss with no evidence of external leaks.We suspected a bad head gasket, and the coolant loss was confirmed after I pulled #2 plug first thing in the morning to find 1/4" of coolant in the cylinder through the spark plug hole.

I proceeded to remove the head, all the while thinking of a similar job I did for a customer 3 years ago with the same year/make/model and same symptoms. That customer's issue turned out to be a pinhole leak in the aluminum head casting of cylinder #2, just next to #1 intake valve's guide, which dripped coolant into the combustion chamber over night and misted coolant while running, causing misses and rough starts.

To my surprise, I found a stain of coolant in the exact same spot, and burnt/ caked coolant on the stem and fillet right up to the seat on cylinder 2 intake valve #1. Thinking this is more than coincidence, I searched for others with the same problem and it seems as though the AMB motors have a bad batch of heads that either crack over time or have thin walls to the water jackets around #2 causing this hard to diagnose problem.

In both cases, I replaced the heads with VW 1.8t heads and so far, so good.

jeff.



hi, sorry to bring this back from the dead, but i'm just curious on how much this type of job costs, head replacement and all?

thanks in advanced.

MC Hammered

  • Posts: 1177
I had the same issue with my head with a crack letting coolant into cylinder #2.

Instead of replacing the head I ended up rebuilding it for a BAT swap and fell down the slippery slope on the quest for power.

I would have saved so much $$$ and probably still own my Audi if I just swapped the head with a VW one.