Engine rebuild with no former experience........

Hi Jim,

after researching a bit I found out that hexavalent chrome (here represented by sodium dichromate) seems to be banned nowadays and I almost believe that is quite right too. I mean, chrome generally is not very healthy but, god, Jim, this stuff is f..... poisonous, even the fumes could harm you!
What did you dislike about the trivalent chrome passivation? And what is your recipe for the trivalent chrome passivation?

Regards,
Lutz

Yes Lutz,
Thats the reason I stopped doing this...

Plating itself is not the problem, to get the yellow shine is the problem.
I always was wearing a very good mask with filter, but I still had bad feelings.

Hi Lutz, yes, all these chemicals are dangerous, anyone considering using them needs to understand the danger, risk and how to use PPE and ventilation to mitigate them.

I have worked in labs for many years and my wife has worked in a bio-chemistry lab for 40 years, many times with sodium dichromate, so we understand the risk.

Anyone who has watched the film "Erin Brockovich" ( en.wikipedia.org/wiki/Erin_Brockovich ) will have heard about the dangers of Sodium Dichromate, however it is still a widely used chemical and is free to buy, see here sodiumdichromate.co.uk/

As for the trivalent solution I tried, it gave a mainly pink colour with just a bit of gold rather than mainly gold. I purchased a ready made up solution so am not too sure about its exact make up, however I do have a safety data sheet for it. I will look that out and post up the details later.

Edit

I checked on the contents of the original yellow passivation that didn't work too well, it turned out not to have any chrome in it.

It contained, nitric acid, selinium dioxide and ammonium biflouride.

For anyone wanting to find out more on electroplating I found this free download book.

www.engineeringbookspdf.com/workshop-pra...s-11-electroplating/

Hi Jim,

of course all the chemicals you are using are dangerous but sodium dichromate is on top of the top, I would say.
Strange that it is sold to everybody in the UK while every company that wants to use it, needs a permission since 2017. Well, maybe not in the UK any longer but within the EU.

I wouldn't care about a yellow or blue or whatever shine, important is the passivation after the zinc plating to protect the zinc from corrosion.

Because of the banning of sodium dichromate more companies seem to use thick layer passivation. It seems to be even more durable than the hexavalent chrome passivation. Has anybody looked into this?
I found a company that sells a ready-made solutions that claims to be a thick layer passivation based on trivalent chrome:
www.tifoo.de/blauchromatierung
The also have a yellow passivation based on trivalent chrome.

Regards,
Lutz

Looks like a safer option Lutz (I hope you are not a smoker).

Today I had a look at the old and new piston ring gaps. All were set to the same position in the cylinder using the piston as a pusher.

The min - max values are

Top ring 0.3mm to 1.0mm
Mid ring 0.35mm to 0.8mm



This is the old top ring, 1.45mm way over the limit.



The old middle ring, .8mm, right on the limit.



The new top and middle ring were both the same at 0.5mm



I will check the rest of the new ones later as I wanted to get on with chasing out all the block threads before pressure washing the block tomorrow.



Tomorrow will be the first warm day (8degC vs 0degC) for a while, so I will wash out the block and heads so they are clean prior to reassembly.

Hello,

did you checked the ring gap below bdc in the liner?
This are has the lowest wear so you see the smallest gap.
Just to avoid to small ring gap and resulting difficulties with your new rings.

I would debur the edges of my new ring with a diamant file. In many cases the ring edges are very sharp and cause scratches in the line......easy to avoid.

Kind regards

JP

No, just a quick check at the oil ring level at tdc. Thanks for the tips, I'll check as you suggest.

Racediagnostics schrieb: Looks like a safer option Lutz (I hope you are not a smoker).

No, I am not, are you? Otherwise I wouldn't have to worry about a bit more or less chrome in my body .....

Regards,
Lutz

No I don't smoke but have been an electronics hobbyist for 45 years, I dread to think of how much solder flux smoke I have breathed in over that time.

Final clean for the block, heads and intake manifold today. Finished off with hot water, compressed air, wd40 then some oil.

Here is a look inside the block, nice and clean and no crud after power washing.



The first job was to clean out the flash rust from the bores. I saw a video on youtube suggesting using ATF and coffee filters. ATF due to its corrosion inhibitors and coffee filters due to its lack of lint.

The video suggested wiping till the filters stayed clean. It didn't really look like there was any but....



Before and after results.



Next I fitted the new crankshaft bearings. Spot the error?





I did a test fit and measured the bore with the new bearings, all looked good, pretty much 64.00mm on all bearings.

That brought the clearance back into spec, red line to green line below.



As a double check I then fitted the crankshaft dry with plastigauge.





They were all between the 0.038mm and 0.05mm indicators, so in line with my measurements.

Finally, after 2 months and 2 weeks of strip down and prep, the engine is ready to be rebuilt.



First this crankshaft sprocket.



It wouldn't slip on as described in the manual, so gave it a gentle heat, not enough to melt my gloves as its hardened.



Even heated it still took a hammer and cup to get it fully seated.



Next the crankshaft fitted to the block.



Then on to the piston rings.



First one knocked in.



Torqued up plus 90deg.



That feels like a milestone, all pistons fitted.

I rebuilt the heads today but came across a new problem.





You will see that 3 of the cam towers are missing. I was able to buy replacement for these from ebay, same part number stamped on them as the old parts but it turns out that what was supplied are 0.1mm undersize. Old ones are 49.4mm diameter, the replacements are 49.3mm.

So I have two options, get the three journals ground down by 0.1mm (would be good to get rid of the scoring on the journals), or reuse the old worn bearings. One issue I see with getting the cam journals ground down is, will the engine shop be able to keep concentric with the other journals?

Not much progress today, life outside the garage interfered.

Lower chain guide rails.





New front crank seal.



Tapped into place.



Finding TDC.



Lining up the distributer sprocket, I'm not sure why it needs to be lined up.



Back of the crank seal filled with grease to stop the spring popping out when mounting. Rubber grease holding in the O rings. Oil pump chain guide fitted. Now there was no gasket on the timing cover when I took it off but the manual calls for a sealant to be applied when replacing.

I have this Permatex gasket maker or can pick up some Loctite 5980 from Halfords, any thoughts?



New idler sprocket.

I ended up using a thin bead of 5980, I don't want blobs falling off into the oil pan.



Turns out you need at least 6 hands to fit the timing cover, I'm glad a tried a few test fits before using the sealant, the main problem is that the oil pump chain gets in the way. Anyway, it's now fitted along with the crank hub and water pump.

And everything is nice and shiny .....

Regards,
Lutz

I went backwards today, while looking at the oil pump mounting points noticed this debris in the oil channel that leads from the pump. It's glass beads left over from the vapour blasting.



So the timing cover had to come off for cleaning.



Despite only putting on a small amount of sealant towards the outer edge you can see that plenty made its way into the inside of the timing case, not good!



I cleaned off all the Loctite 5980 and instead brushed on a small amount of Permatex Aviation.



Back together again with a few more ancillaries attached.

Having spotted the glass bead in the timing case cover I thought I would do a double check on the inlet manifold that was also blasted, as well as the inlet runners (that are easy to clean out) there are two internal tubes that run the length of the manifold that are used for the cold start injector.

I gave it a power wash last week but thought a double check was in order.



There is a core plug at the end of this internal tube so I pulled it out with a slide hammer.



Glad I did as it was packed with glass bead.



I got it cleaned out but will give it another power wash tomorrow. These plastic number plate screws were the perfect size to plug the holes that connect the runners to the internal tube.



Looking down the length of the tube, now perfectly clean.



I then moved onto the old sump gasket, it seems to have morphed into igneous rock over the last 40 years, I think this will take most of tomorrow to remove.





I also dropped the CAMs off at the engine machine shop this afternoon for the end journals to be ground. They will hopefully be ready on Wednesday.

I ran the lockdown gauntlet and picked up the pipework from the platers this morning. £120 cash, its not perfect, there are a couple of rusty spots but I will be able to fix these myself as they are close to the ends.

Ideally they should have been vapour blasted first but the cost including that was £278 so I opted for just a dip strip and plate passivate.



Then onto the sump for a couple of hours, the best technique I found was keeping the scraper at just the right sharpness. I didn't use any gasket remover as other who have tried on these said it made no difference.





Next onto a couple of the fuel hoses, these are the parts I stripped off the old hoses.



I heated the hose and got the first end pushed in most of the way but not all the way (bottom left), any suggestions on the best way to push these in, I may just nip along to a hydraulic shop tomorrow and get them to do it. The other ends are just sitting in place.

Hi Jim,

what I do in such a case is that I insert the hose into 2 vice jaws with a proper slit for clamping hoses (not sure that my own brain translator is doing a good job here, so in German It means "Schlauch in einen Schraubstock mit geschlitzten Backen zum Einklemmen von Rohren einklemmen"). I let it stand out a bit hold the hose connector to it and use a PA hammer to insert it cm by cm taking out more and more of the hose from jaws while inserting the metal connector by hammer. That is the way how I do it with PA hoses and connectors for the K-Jetronic manifold. You can see that here in paragraph 3: Bauplan eines Manometers für die K-Jetronic

Hi Jim,

Gullydeckel-Martin, who once ordered the hoses for us, recommended using brake cleaner before pushing on the hoses. Makes it easy to get them on but has no lubricating substances that could weaken the stability of the connection.

Regards,
Lutz

Thanks guys, I tried that technique and it worked.

I admire what you are doing, wouldn`t have 10% of your energy and your skills !

Kalli

Skills can easily be learned, I had never worked on a car before I bought this one. Time cannot easily be bought though, and this hobby is very time consuming. I am very thankful for early retirement.

Killing time this morning before heading to the machine shop to pick up the CAMs.

Starter motor and solenoid bolted back together.



Need to sort out a couple of new screws there.:ashamed:



The full engine rebuild gasket set wasn't as full as it could have been, so cut out a couple of new gaskets.





Oil pump damper back together.



Then off to pick up the CAMs. The left CAM perfectly on the target size. And rotates perfectly with all the cam towers bolted down.





The right CAM is not so good news, it has had the leftmost two journals ground (1 and 2). The far left is perfectly on size at 49.275 but the next one in is oversize at 49.28, however even with that there should still be a bit of clearance if everything was concentric. When I tighten down tower 2 (with the others already tightened down) the CAM shaft binds up (worked it out through a process of elimination). It's no big deal and I am sure the machine shop will be able to sort it out, but they are now closed till next Monday so I will have a bit of a delay.

All's well that ends well.

We can assume that new set of bearings from Mercedes will be concentric.

We can also assume that there may/will not be concentricity between two different sets, regardless of whether they are the standard size or undersize. This can be deduced from the fact that Mercedes will only sell a full set.

So mixed sets will have the chance of not being concentric.

When fitting a new undersize bearing set, you must grind all the journals at the same time on the same set up to ensure concentricity.

If you only grind one or two you are guaranteed to have some amount of non concentricity between the journals.

What happened to me was very unlucky, I ordered (from ebay) what I thought were 3 good standard size bearings that turned out to be undersized, non concentricity factor 1.

As a consequence I needed to grind 3 journals on the CAMs, non concentricity factor 2.

The only machine shop I could find that was open (covid) was one I said I would never use again, non concentricity factor 3 as well as grinding one of the journals over size.

From that it is clear that I would be very lucky to have no issue with binding, and I'm not that lucky, so this is what I did today.

Blue up the bearing.



Bolt it down.



Give the CAM a half twist and review.



Then use my contraption with 400 grit emery and a scotch pad applying pressure where needed (yes I know I lots of people will say DONT USE A SCOTCH PAD!) to get rid of the binding spot. It took 5 iterations to get the CAM to rotate smoothly. The bearing was cleaned each time till there were no traces of sanding material.





All done, almost.



Once that was complete I also did a bit of work on the other two bearings with the blue to ensure they were also running perfectly.

Jim the researcher!
Through the scotch pad method you probably took off material not only from the binding spot but everywhere, right?
How can you now know how good the result is (overall tolerance and overall concentricity)?

Regards,
Lutz

Hi Lutz,

No, the bearing tower was not tight on the scotch pad and mandrel, so it was easy to provide force to any quadrant needed to focus on the problem area.

With the bearing in the pictures above I started off with a clearance of 0.02mm which was one of the problems, the minimum should be 0.025mm.

The clearance specification is actually quite wide, 0.025mm to 0.057mm, so removing ~0.015mm of material still leaves me well within the tolerance.

Also, once the engine is running the aluminium bearing expands at twice the rate of the steel CAM shaft, so I have no worries about normal hot running.

I do not have perfect concentricity, but I am not worried about this.

To do this job properly ideally you would buy two new CAMs, two new bearing sets, 16 lifters and ?? shims, ~ £2500, my fix cost £160. Undersize bearing sets are no longer available from Mercedes unfortunately.

Hello Jim,

I would be not to concerned about your "rework"

If you are with tolerance limits and the cam is turning freely in the bearings/ towers everything seems to be aligned good enough.

Just would check if the cam is turning freely in the towers before assembly.
During/ after engine recommissioning listen for any abnormal noise and take the valve cover off and take a quick temperature check of camshaft and bearings/ tower just to check for high temp i.e. friction.

Just make sure the surface of the bearings is free from any scotch pad residues.......your engine would not like this material in the oil circuit.

We scraped bearings on large two stroke cross head marine diesel engines.
When I did this the 1st time I was a little hesitant.......but with advice from my Chief Engineer this worked our very well.
Just need to know what you are doing.

Kind regards

JP

All the new bolts organised for the rebuild.



I was surprised to see that the pistons sit proud of the block at TDC, given there is no recess in the head, that's cutting it close with the thickness of the head gasket, the spec says 0.75mm max projection.



Head ready to go on.



Head in place.



Various brackets and starter motor heat shield held on with head bolts.



Out for a Covid lockdown walk.



New chain guides and sprocket, with head torqued down, the CAM shaft still rotates smoothly!



Other head sat in place, initially I thought "great, the chain meets up as expected", more on that later.



Next a quick check on the timing marks at TDC, left head (from the front of the engine), good.



Right head, good.

Looks like the timing spike on the aftermarket water pump is a bit off, as I know the engine is perfectly at TDC.



So the problem is, the chain is too tight or too short, this is the post on the chain tensioner rail, it should be recessed in the head about 1 or 2 cm. Now I have still to torque down the head but I cant see that giving much more slack! Confused.



The chain is a Febi which should have 198 links which is correct, but I didn't count them.



I'll need to get an endoscope in there tomorrow to work out what is going on.