W124 Idiotic mistake. Missed timing chain cover bolt when lifting head and... 'CRACK'

[RogK]

Please don't laugh (or cry) too hard - I'm a newbie in distress.

Was lifting the head off my 2.3e in the cold and the dark. Forgot to remove the timing chain cover bolt by the guide rail and only went and broke a chunk off the timing chain cover. Actual head (as in everything but the broken cover) is very good.

So, my thoughts are; the timing chain cover isn't under pressure but is getting sprayed with hot oil. Maybe it can be saved? I've received about 50/50 advice between welding it up (thin cast aluminium - tricky) and bonding the chunk back in place with jb or similar. An MG old-timer who looked at it for me figured it was the first time he'd ever seen a job suitable for metal epoxy!)

My question is am I right in thinking the front cover isn't under huge pressure? Advice & opinions graciously received!

(and yes... I know... I'm an idiot...)

 

[markjay]

Ouch.

Can you post a photo?

 

[RogK]

Ouch.

Can you post a photo?

Will do

 

[RogK]

Scene of the crime

 

[Mactech]

There are some astonishingly strong bonding agents now available which will not cause the problems of heat and distortion of welding.
They all rely on one fundamental, a forensic cleaning of the parts involved prior to application. That is the route I'd be heading down.

 

[Tonye]

JB will sort that out no problem.

 

[vijilants]

I'd speak with an aluminium welder and see if they can fix it without causing any more damage.

After all, they weld alloy wheels without causing distortion.

 

[Phil1968]

I'd get it welded. At least then you can be pretty much 100% sure that it won't fail. Unlike the epoxy repair.

 

[RogK]

Thanks all. I hope to get a welder to look at it this week. I'll report back with pics.

Head must have had a gallon of k-seal put through it. Water lines were absolutely clogged with the stuff. Real shame as valves, cam and head were all otherwise perfect. Still, not as bad as me cracking the damn thing I suppose.

 

[markjay]

Cam covers are usually fastened with a large number of bolts spread evenly along the circumference and tightened with low torque (typically 8NM). So strength won't be an issue if using J-B Weld.

BUT - the reason for this layout is to prevent leaks. If the surface isn't 100 flat and 100 clean of corrosion, the cam cover will leak (and many cam covers these days use RTV sealant instead of a gasket). For this reason I'd get it properly MIG welded by a firm that refurbishes cylinder heads, and also get them to skim the mating surface to ensure it's flat.

 

[Will]

I’d check the head over carefully for corrosion etc before worrying too much about the chunk damaged at the front. You can see some surrounding the coolant passages next to the combustion chambers, usually on the 8v M102 they are worse towards the rear of the head.

If all salvageable, I’d look at getting that chunk welded and it can be machined flat when you get the head skimmed/re-faced prior to assembly.

Remember to carefully clean the threads in the block out, measure the bolts or ideally replace and use an OE Elring gasket only.

55Nm, 90, 90 for the head bolts - check the torque setting for the timing case area ones. It’s more than 8Nm, might be 20-25 from memory.

Make sure you re-set the chain tensioner before you re-assemble - very important (!)

Worth draining the block out and flushing the heater matrix through with a hose if someone’s had K-seal in there

Once it’s all clean, and after it’s reassembled I would use citric acid and flush the whole system through a couple of times and then flush with more soft water before refilling with the correct coolant.

Good luck

 

[markjay]

....It’s more than 8Nm, might be 20-25 from memory....

You're probably right.

Last time I did this was only over 10 years ago

 

[Bellow]

How highly stressed is the (broken through) boss retaining part of the tensioner assembly?

 

[Will]

How highly stressed is the (broken through) boss retaining part of the tensioner assembly?

It’s for one of the pins for the guide rail. It’s not under tension (from the chain), just a plastic chain guide on the return side away from the tensioner.

Those guide pins are usually a tight interference fit in those bosses though, so will definitely need welding and the hole machining back afterwards.

Well spotted though

 

[RogK]

How highly stressed is the (broken through) boss retaining part of the tensioner assembly?

Bit concerned about realigning it alright... I remember drilling out an alignment pin years ago; replacing it was not fun..

I’d check the head over carefully for corrosion etc before worrying too much about the chunk damaged at the front. You can see some surrounding the coolant passages next to the combustion chambers, usually on the 8v M102 they are worse towards the rear of the head.

If all salvageable, I’d look at getting that chunk welded and it can be machined flat when you get the head skimmed/re-faced prior to assembly.

Remember to carefully clean the threads in the block out, measure the bolts or ideally replace and use an OE Elring gasket only.

55Nm, 90, 90 for the head bolts - check the torque setting for the timing case area ones. It’s more than 8Nm, might be 20-25 from memory.

Make sure you re-set the chain tensioner before you re-assemble - very important (!)

Worth draining the block out and flushing the heater matrix through with a hose if someone’s had K-seal in there

Once it’s all clean, and after it’s reassembled I would use citric acid and flush the whole system through a couple of times and then flush with more soft water before refilling with the correct coolant.

Good luck

Many thanks. New stretch bolts are on standby, as is the Mercedes lemon juice (doesn't half sting in a cut). Lapping paste at the ready, new water pump, gaskets for everything, and so on! A lot of what looks like rust is non-metallic mystery powder... I've a decent machine shop close by that did a great job before on a 190 head skim and thoroughly cleaned it, so I'll go with them.

Big thanks to all for advice and for not giving me too hard a time

 

[Bellow]

Is there not a second-hand head available and rebuild it as you intend doing with your existing one? One from a car that has blown its head gasket may require a skim (required for yours anyway) and the level of distortion (if any) should be measurable before buying. Your cam and followers can be carried over to the replacement head. Lap the valves and you're good to go.

 

[optimusprime]

A good replacement second hand cover, is the best way to go . Repairing would cost as much . And i would not even think about welding it . You need to pull it off to repair it so no time lost .

 

[grober]

It’s for one of the pins for the guide rail. It’s not under tension (from the chain), just a plastic chain guide on the return side away from the tensioner.

Those guide pins are usually a tight interference fit in those bosses though, so will definitely need welding and the hole machining back afterwards.

Well spotted though

https://www.startekinfo.com/service/download-document/outside/11832/Resources/201Create/PDF/30005.pdf

 

[markjay]

A good replacement second hand cover, is the best way to go . Repairing would cost as much . And i would not even think about welding it . You need to pull it off to repair it so no time lost .

From the photos, it's the cylinder head that's broken, not the cam cover (sod's law)?

 

[grober]

Removing upper timing chain guide rail pin - 1993 190E M102 engine | Engine
the problem was you didn't remove the timing -chain guide rail pin/s which effectively attach the front of the head to the block before lifting the head causing the head casting to fracture- best now with a replacement head the 2 litre won't fit the 2.3