n42/n46 Engine Rebuild

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Bought my car over a year ago, and have been steadily maintaining it as the previous owners sure didn't.

Was a bit smokey due to lack of oil changes, and probably incorrect oil.

So far it has had a new oil cooler, ccv valve, oil hoses, drive belt and plugs.

I have rebuilt and put new viton seals in the vacuum pump, and I did all new seals on the vanos and cam sensors, and the seal on the dipstick tube. All new seals are viton.

I've also done the whole cooling system, with new radiator, water pump, expansion tank and hoses and seals.

Glenn from Botany Motor Worx has been extremely helpful with advice and diagnosis.

So......now its finally time to do the valve stem seals.

This is expensive, and not a diy job, so I hatched a plan.

I will rebuild another head or complete engine and then swap them over.

I got a complete n42 engine (the one in the car is n46 but they are almost identical.) for just $150.

Time to strip it back and inspect it

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First thing I did after I got it on the engine stand was degrease and water blast the exterior of the engine.

Then I took the valve cover off.

There was a lot of sludge - not the worst I've seen, but still plenty of sludge.

The engine was sold as a runner, albeit a rough one with 155kms on it.

The first thing I noticed was the plastic guide rail for the chain was damaged - this is very common on these engines.

Then it was time to take the head off and check the bores.

There was a lot of carbon on the pistons and valves, but the bores were in perfect shape.

Then I took the sump off and had a look. Looked pretty clean and the bearings felt good.

Next job is to take the head into a machine shop to get it checked.

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Took the head to Mark Wade of Wade Automotive in Penrose. He has been building engines for the race industry for decades.

A bit grumpy, but very knowledgeable and experienced.

He checked the head and also resurfaced it.

This cost $75 + gst which I thought was reasonable.

He checked the valve guides and said they weren't perfect, but not bad enough to need replacing.

He checked the valves and seats too, and said they needed a valve grind.

This is something I was going to do anyway.

He said the hydraulic lifters were ok, but I'm going to rebuild them anyway. It only costs me my time.

If its worth doing, its worth overdoing.

The head looked good after it was decked, but unfortunately my photo skills were not quite so good;

Then it was put in my diy parts cleaner along with the cams and a few other parts.

Basically its just a tub from Bunnings filled with simple green - this stuff cleans off carbon and grease very effectively.

For less than the $60 + gst cost of getting my head acid dipped at the machine shop, I have the ability to wash as many parts at home as I want, and in my own time.

Next job is rebuilding the lifters, cleaning the valves, and a valve grind.

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Well, the diy parts cleaner worked brilliantly!

The parts came out super clean without even wiping them.

The only parts that needed a scrub were the exhaust ports on the head, where the carbon was heavily burned in.

The parts cleaner loosened most of it, so I gave the exhaust ports a scrub and put the head back in the parts cleaner for another soak.

The cams and valves and the other parts came out spotless.

I am halfway through rebuilding the hydraulic lifters.

Basically all you are doing is disassembling, thoroughly cleaning them out, reassembling, and pre-priming them.

Carbon and sludge gets in them and stops them working properly, and are a very common fault on this and some other bmw engines.

Sure, I could buy new ones, but this is free and I'm enjoying learning new stuff.

This engine will be built on a budget, but definitely not by cutting corners.

I did a lot of reading on rebuilding lifters, and this video was very helpful;

https://youtu.be/ySf0r8GGMOY