timmus
A2OC Donor
A few months ago, I mentioned that I was losing coolant. There didn’t appear to be a pool of liquid forming anywhere easily visible. However, there seemed to be a direct correlation between how hard I drove the car and the rate of coolant loss. Spike correctly diagnosed the problem; cylinder head gasket failure!
So, while my A2 was at Stealth for its gearbox upgrade (see www.a2oc.net/forum/showthread.php?21523), I had Vince solve the problem. Never one to do things by halves, I had the cylinder head completely rebuilt, prompted in part by a broken valve.
The photo below shows the engine bay with the cylinder head removed. The detached cambelt can be seen in the top-left-hand corner. The three heater tubes on the right were replaced, as they’re inaccessible with the cylinder head in place. Because the gearbox has been removed, one end of the engine has to be held up with a chain. It’s possible to see the fuel swirl chamber in the top of one of the three pistons. The unit injectors mist the fuel into this little space.
Once removed, stripped back and cleaned, the 3-pot TDI’s cylinder head looks like this. You can see the holes for the valves as well as those for the fuel injectors.
The underside of the head, once skimmed, looks like this. The tiny holes between each pair of valve holes are where the spray tips of the fuel injectors pop through into the combustion chambers.
When Vince dismantled the head, the little ribbed end of one of the valves broke off. The photo below shows shiny and dull parts of the break, suggesting there was a manufacturing problem with this valve, leading to a hairline fracture. Vince said that he'd never seen this before. Had this happened while the engine was running, the rest of the valve would have fallen down inside the combustion chamber, which could easily have ruined the engine.
So, a new set of valves was purchased, along with new concentric springs and all the other little bits and pieces.
Vince also found that the camshaft bearings were showing signs of wear, so these were also replaced. In the photo below, you can clearly see the wear to the plain bearings, in addition to the fuel injectors down the left-hand-side.
So, while my A2 was at Stealth for its gearbox upgrade (see www.a2oc.net/forum/showthread.php?21523), I had Vince solve the problem. Never one to do things by halves, I had the cylinder head completely rebuilt, prompted in part by a broken valve.
The photo below shows the engine bay with the cylinder head removed. The detached cambelt can be seen in the top-left-hand corner. The three heater tubes on the right were replaced, as they’re inaccessible with the cylinder head in place. Because the gearbox has been removed, one end of the engine has to be held up with a chain. It’s possible to see the fuel swirl chamber in the top of one of the three pistons. The unit injectors mist the fuel into this little space.
Once removed, stripped back and cleaned, the 3-pot TDI’s cylinder head looks like this. You can see the holes for the valves as well as those for the fuel injectors.
The underside of the head, once skimmed, looks like this. The tiny holes between each pair of valve holes are where the spray tips of the fuel injectors pop through into the combustion chambers.
When Vince dismantled the head, the little ribbed end of one of the valves broke off. The photo below shows shiny and dull parts of the break, suggesting there was a manufacturing problem with this valve, leading to a hairline fracture. Vince said that he'd never seen this before. Had this happened while the engine was running, the rest of the valve would have fallen down inside the combustion chamber, which could easily have ruined the engine.
So, a new set of valves was purchased, along with new concentric springs and all the other little bits and pieces.
Vince also found that the camshaft bearings were showing signs of wear, so these were also replaced. In the photo below, you can clearly see the wear to the plain bearings, in addition to the fuel injectors down the left-hand-side.
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