Has anyone run water injection to help with the valve carbon problems on the 4.0? Top end cleaners burn up in the chamber, but water turns to steam, which softens and in turn burns off carbon - even on the exhaust valves. We used to run it in the 80's when we had fuel quality problems.

 

Have not heard of anyone one running water. BMW fixed the carbon stick problem with the introduction of new valves and guides. The older engines ran very rich and the valves did not reach the temps required to burn it off.

 

Yes, BMW switched to a sodium filled valve which spread the heat load evenly. BMW also had an engine recall in which we walnut shell blasted the valves.
"( Note: Carbon Buildup was a common problem for the E28 535 caused by
poor fuel quality. Many BMW's experienced rough idle due to carbon buildup
while still under warranty. It is recommended you use premium gas at least
once in every 4 fill-ups. The premium gas contains more detergents to remove
the carbon deposits from injectors and gum/varnish buildup on valves. That
said however, some Oil Companies add no additional detergents to their
regular or premium fuel products... Ask your fuel company for information.

BMW NA undertook an engine campaign to pay for the removal of the inlet
exhaust and sand blasting to the back of the valves with crushed Walnut Shells."

They were also responsible for forcing refineries to make higher quality fuels.

In my own observations, I have torn many engines apart since the mid eighties. I have seen some with carbon so bad on intake and exhaust valves that there was almost nowhere for air to get in and out. I ran water injection on carbureted cars years ago, and as part of a "tune up" back in the day, I used to pour a half gallon into the carb (slowly) as the engine was running to decarbon.

What made me think of it this time occured during my reserch into buying my Rover this week. I can weed through "I hate my car because I won't spend the money to fix it right or heaven forbid actually maintain it" articles, but the carbon issue keeps coming back. On Wednesday I pulled the head off a 535i that has had a slight combustion chamber coolant leak for about three months. When I removed the head, there was slightly more than normal carbon build up, with exhaust valve deposits - except for #5 and #6, where the coolant (a quart per week) was leaking in. They were clean and shiny, with valves and chambers that look like new. I remember seeing the same thing in almost every slightly leaking head gasket I've pulled apart. Most modern cars (that I work on) run the chambers so lean and hot they never build up.

Here is what I'm going to do. I'm going to run the boroscope down a cylinder of my 97 Disco when I get it to inspect the valves. Then I'm going to fabricate an injection system usind a 4:1 mix of water and alcohol. I'll run it a few weeks and reinspect. I'll also run my GTech meter on the truck to see if there is any performance enhancements.

 

BMW never spec'd a sodium filled valve to fix a Rover. They did spec new coated valves and guides. To date, this has rectified the issue. Fabricate what you want, it is a design flaw.

 

Sorry, I thought you were talking about the carbon problem from the 80's on other "brand X" engines, and what was done to overcome those design flaws.