Kablam !! Big bang. Cracked valve cover - PeachParts Mercedes-Benz Forum

#1 06-12-2002, 12:49 AM

As if things weren't bad enough with one benz sitting dead in the driveway with a broken fan belt that I can't fix, the other one blew up on me on my way home.
Barrelling down the highway and five minutes from home I heard a noise like a bomb going off accompanied by a nasty clatter and a puff of smoke in the rear view mirror.
It died right there and I rolled to the side of the road.
The front of the valve cover right above the timing chain is cracked so I had it towed to my driveway.
Diagnosis ?
I'm assuming the timing chain broke.
Further diagnosis ?
Did my pistons then hit my valves 'causing me to need a rebuilt head ?
Would it be likely that I damaged the crankshaft at the same time ?

Prognoses ?
Anyone ?

Thanks for any and all speculation.

jim

tcane · #2 06-12-2002, 02:03 AM

Valve cover breaking where it did would seem to be the timing chain. However, like a surgeon doing exploratory surgery you will need to at least remove the valve cover to actually see what broke. After removing the valve cover, other parts will need to be removed to find out what went wrong and find all the parts that are damaged. This process can include a complete engine tear down depending on how extensive the damage is.

As I wrote in your post about fans belts, you need at least the Haynes manual and probably the official M-B manuals now.

Good Luck!
Tom

#3 06-12-2002, 02:52 AM

And once again thanks Tom.

Yeah. I decided a long time ago that Haynes manuals are only sometimes useful. I've bought one for practically every car I've ever owned 'cause they do have some good info in them. They worked out well for me when changing the head gasket on my son's Honda Accord and they are usually pretty good for brake jobs I've found, but on the whole I don't like them. Their pictures are grainy, they leave out an enormous amount of information for a DIYer like myself and exploded parts views are nonexistent.
Long and the short of it is, I guess I've got to spring for a shop manual.
Jim

tcane · #4 06-12-2002, 04:00 AM

Jim:

I agree, that many manuals have their short-comings including the Haynes. But, I used some of the first Japanese manuals translated to English - talk about hard to use and understand. Wait till you get the M-B manuals - very cryptic, assume the reader has a good foundation as a tech, and the CD's pictures are bad. Compared to the M-B repair CD's, the Haynes manual is a model of clarity and great pics. But, the Haynes manual certainly does not have all the info the M-B manuals do, but what the Haynes has is a lot easier to find and understand. The M-B print manuals are OOP which is too bad since the pics are much better and I like being able to flip the pages to find stuff and go back and forth between different but related service/repair operations. You can find the M-B print manuals on eBay along with the CD's (and a lot of CD-R's). There are 5 print manuals for the W123 turbo: 1 engine, 2 chassis (has the power steering info among some other stuff connected to the engine in some way), 1 AC manual, and 1 electrical manual (mostly wiring schematics with some pics and a layout showing where things are located - but not a good manual for most DIY folks). The CD repair info comes on 2 discs with every W123 model 1977-1985, whereas the engine print manual has two versions - one for the turbo engine and one for the non-turbo. As far as I know the other print manuals are the same for the turbo and non-turbo W123's. The print manuals can cost more than the CD's, but if you look the print manuals can be found reasonably. Do a search here for some info by members about the manuals and where to find them.

Good Luck!
Tom

#5 06-12-2002, 04:40 AM

Sorry for your loss.

If your valve cover is cracked, the pistons hit, valves bent and your camshaft is probably in 2 or 3 peices.

#6 06-12-2002, 05:38 AM

Sorry to hear about that, it doesn't sound good at all....on the bright side, I have two cylinder heads for sale! Both came off a running engine, one is complete one is not. Let me know what year car you have and if you decide you need one. I have them posted in parts.

kershubby@hotmail.com

#7 06-12-2002, 08:35 PM

yup !

TURBODIESEL SAID

"If your valve cover is cracked, the pistons hit, valves bent and your camshaft is probably in 2 or 3 peices."

You got that right. Amazing to see a quality piece of steel like that camshaft sheered in half.

I'm going to have to do something with the head obviously.
Have mine rebuilt ?
Buy a used one ? Rebuild it ?

brandoncrone I'm a long way from your neck of the woods and I'm hoping I can find something closer to home. Thanks for the sympathy and I may call you on your offer if I'm unsuccessful locally.

Tom you said

"Valve cover breaking where it did would seem to be the timing chain. However, like a surgeon doing exploratory surgery you will need to at least remove the valve cover to actually see what broke. After removing the valve cover, other parts will need to be removed to find out what went wrong and find all the parts that are damaged. This process can include a complete engine tear down depending on how extensive the damage is."

Well . . . hmmm ?
Can you tell me how to check below the head for damage.
I guess it's self-evident that if the camshaft is broken then the valves are toast too ?
And that I need a refurbished head ?
I know I can check the piston tops once I pull the head but the other stuff ( rods, bearings, crankshaft itself) ?
Is there a method for diagnosing those items without a complete teardown ?
Appreciating your time and careful replies very much.

jim

Billybob · #8 06-12-2002, 08:56 PM

Been a couple of 5 Cylinder heads on E-Bay lately some didn't sell so you might be able to do a search and then get in touch with the seller. I assume you will have to aceertain whether the pistons, rods, or crack sufferd any damage also! If so then and engine swap might be reasonable if the chassis is worth it. Good Luck!

#9 06-12-2002, 09:55 PM

I may check that out.

tcane · #10 06-13-2002, 03:59 AM

Jim:

Sorry to hear the cam broke - not a good indication of other parts not being damaged. If the timing chain just broke and flung around cracking the valve cover and a few bent valves then fixing your head or replacing it along with the chain and tensioner and guides may have put you back on the road.

But, breaking the cam takes a lot of energy and one or more of the rods could be bent along with probable damage to the piston crowns (need to look at them to know how bad). Even if the the pistons look like they come all the way to the top of the block there is still a chance of bent rod(s) especially if the piston crowns are damaged. Worst case, the crank could be damaged also. Let's hope not, but the only way to know is a TDI (tear down and inspection) because the only way to inspect the pistons, rods, crank, etc. is to remove the engine. The engine comes out as an assembly with the trans connected. The Haynes has very good info on how to R&R. I made a post a while back on making a chain sling to pull the engine/trans out at the 45 degree angle unless you have one of those slings that rotates like the M-B sling does.

If the lower end is OK and you need a replacement head then figure 93 pounds for the complete head (head, valves, springs, camshaft, cam towers/bearings, etc., but not the valve cover). Once the head is crated for shipping figure at least 100 pounds or a bit more. If the head can be rebuilt, cam costs about $150, cam bearing set $120, valves are $15 ea. intake $30 ea. exhaust, guides about $3 each, plus cost of any other parts damaged and then labor to replace the parts (magnaflux head for cracks, replace guides, grind valve seats, lap valves, etc.).

If the lower ends needs work, then you may want to balance how long you want to keep the car versus the cost to rebuild your engine and if that is too much then buying a used engine from salvage ($150 to $1,000 +) versus a rebuilt long block about $3,300 to $6,000 versus finding another turbo 300D with a good drive train and a bad body (like a rusted out body) for say $500 and up versus throwing in the towel and selling the entire car or parts off it.

A handy reference to get is the M-B catalog of illustrations. This book is the size of the owners manual, but about three times thicker. It has every part, assembly, component in exploded views with reference to the M-B parts micro fiche the dealers used to have. No other info that I've seen shows how the M-B is put together in this detail (engine, trans, body parts, chassis, electrical components, etc., etc.). I bought mine on eBay for about $20 (seen them go for as little as $16 and as high as $50 or a bit more). If you look for this book make sure you get the one covering your turbo engine (mine is for the non-turbo engine).

Tom

#11 06-13-2002, 05:42 AM

I have one question Tom, why do you have to pull the eng and trans together?? I just replaced the engine in my 300D without pulling the trans as well. Seems like a lot of extra work you don't have to do....just a thought.

Jim,

At this point in time, you next move probably should be to pull the head to see what the pistons look like, I've seen many timing chains break, with valves wide open when the piston came up and not do any serious damage to the piston. As these were all mostly gas engines, the pistons on diesel engines are two or three times thicker on the top. I would think that they should be able to absorb an impact like that, time will tell I guess....

tcane · #12 06-13-2002, 02:28 PM

brandoncrone:

The M-B manual shows/requires pulling the engine and trans out together as a unit. I don't own a lift so I was working using jack stands not providing the highest clearance under the car. My big compressor is in storage so I can't use my air driven wrenches. The auto trans has two large bolts at the top that are hard to reach, much less put enough torque onto them to loosen them while laying on the ground (read the problems folks have with loosening the top bolt on the starter that is much easier to reach than the top bolts on the trans.). In fact, most will find they have to remove the trans mounting plate and lower the trans/engine to reach the two top bolts holding them together (ask leathermang/Greg) and then would have to jack the trans back up and re-install the trans mounting plate. I also do not own a transmission jack and I R&R'd my engine by myself. Much less the fact that for me it would be hard to drag the trans out from under the car with it on jack stands because the clearance was not great.

Once the engine/trans is out I found it a lot easier to install the torque convertor to the trans and engage the lugs and also avoid damaging the oil seal, and then lining up the mounting plate on the flywheel to the bolt holes in the torque convertor was also much easier - rather than crawling around on the ground and trying to turn the engine to line up the flywheel to the bolt holes in the torque convertor. Much less the fact I replaced the oil seals in the trans (a good idea since anyone doing this job usually already has a lot of miles on the drive train and the trans oil seals will leak sooner than later, unless they re-sealed the trans recently, and the trans oil seals are cheap).

Many folks believe they are saving time and effort by avoiding removing or taking apart stuff to remove as little as possible and will spend a lot of time and effort doing so. I did this sort of stuff as a pro for many years and although there are short-cuts that will save time and effort, I often found that it took longer to do so than it would have if I just removed everything as a unit.

I know that Larry Bible removes his 300D engine and leaves the trans in the car, but he says he cannot get the engine and trans out as a unit or it is very hard (I forget which since it has been a long time since reading Larry's post on this subject). I can remove the engine/trans as a unit with the way I made a chain sling so the engine will tilt to 45 degrees to clear the trans tunnel and radiator/condensor area. Using my chain sling set-up, I found it relatively easy to R&R the engine/trans as a unit.

That said, you and anyone else can do what they want to. I found R&R'ing the engine/trans as a unit relatively easy versus taking them apart to leave the trans mounted in the car. Seems most folks take great pride in doing things in ways other than what the engineers/techs say to do in the shop manuals - I guess they want to thumb their noses at degreed engineers and techs because they did the job "their" way (Americans traditionally hate authority and their opnions, and so will go a long way to prove them wrong or do things in other ways), and I know that sometimes the shop manual procedure(s) is wrong or harder to do, but not in this case in my opinion. You have a different opinion and others can make up their own mind on what to do.

A member who has not posted in a long time, made a living for 20 + years on M-B diesels and I recall him writing that in the event of really bad timing chain failure the rods can bend even if the pistons don't show much damage (hot aluminum certainly can absorb more impact than the steel rods or crank can and the force breaking a cam has to go someplace). I have seen my fair share of timing chain breaks with valves bent at 45 degrees, big dings in the piston crowns, and no damage to the rods or crank. Here, the piston crown to head surface clearance is very small and no room for things to hit each other much without other things possibly being damaged (like the pistons, rods, crank). I sure would hate to read a later post after an engine was partially rebuit and then failed because it was not taken apart far enough to find all of the damage (here, say a cracked boss where the piston pin goes through the piston, or a bent/cracked rod, or damage to the crank). More damage is a strong possibilty since Anon says he was "barreling" down the road, to me this means he was traveling at higher speeds/engine rpm's that tend to cause much more damage. But, as you said and I did also - only time will tell after taking the engine apart. Hopefully, a top end rebuild will fix the damage and I would urge inspecting the lower end even if doing so requires pulling the engine - but that is up to Anon.

My $0.02 Worth!
Tom

#13 06-13-2002, 05:22 PM

Interesting thoughts on removing the engine and trans as a unit. I had my 300 turbo engine in and out twice this spring. Pulled the engine both times without the tranny because a wise engine guy told me that was best, regardless of the book instructions. As I was staining to get the top trans bolts loose or tightened I wondered just how wise that shop manager really was. Also mating the engine and trans and torquing the flex plate bolts is very difficult under the car. Much less installing the seals.
My question is just how much clearance is there to manuever the assembly out of the engine compartment with that trans hanging on the rear? Do you usually drain the trans fluids before doing so or just use a plug? I do have a lift and engine tilt/sling that functions quite well. Should be of some help.
I am not ready to pull the stuff out again this week, but who knows?

tcane · #14 06-13-2002, 06:29 PM

Old Deis:

I drained the engine oil (hot), removed oil filter, and drained trans fluid but only from the trans to keep ATF spilling out the back seal to a minimum and did not drain the torque convertor (not too long before I R&R'd my engine I'd replaced trans fluid and filter). Left the torque convertor full so it would be easier to fill trans with fluid after the engine started-up. But, you have to keep the torque convertor level or nearly so to prevent fluid from seeping out when it is not connected to the trans (I put a rag over the shaft and propped in an unused area until I needed it). Some may want to drain the convertor to start off with all fresh fluid - up to them.

There is a fair amount of clearance when R&R'ing the engine with the trans attached. Having a sling that rotates will really be a plus - I had to guess where to attach the sling to the hoist and was off a bit when removing (not enough angle) and going in I had the right angle (attached at a point mid-way between the oil filler cap and throttle linkage, but I ended up attaching closer to the oil filler cap). The weight of the trans helps with getting the right angle. As the engine is moved I walked (moved) the trans a bit to help with clearance and adjusted the hoist to clear everything. One thing I did was to use a piece of 1/4" plywood to protect the AC condensor using stretch cords to hold it in place - I needed the protection coming out since the angle was off a bit and the belt pulley and then the lower oil pan rubbed against the plywood. I should have dropped the engine back in and re-attached the sling to get the right angle, but nothing was damaged in any way. Also, my sling split into a Y to connect to the factory connections at the back of the valve cover - this kept the engine from tilting to the side when R&R'ing.

I completely agree with you, I do not want to R&R the engine again unless I have to. That's why I am trying to convince Jim/Anon to make sure he finds all damaged parts and replace/repair to avoid having to do the job twice (or more). With the engine out of the body it sure is a lot easier to inspect, replace, repair, etc. to ensure a successful rebuild.

Tom

#15 06-14-2002, 12:21 AM

I just got in from work and I printed everything out so I can mull everything over before deciding what to do.
Big decisions to make here.
I think I like this car enough to spend the time on it but of course it all comes down to dollars and cents (sense).
I'm only into it for $ 1750 CDN plus taxes.
Oh and about $ 200 in parts, fluids and filters etc.
The body is not bad, better by far than my 1982 so maybe I'd be smart to swap engines though my 1982 is a little high in the mileage. Then I could start looking for a diesel wagon again which was what I really wanted until I found this one. In the meantime thank goodness, the Jag is running beautifully and it gives me an excuse not to sell it.

So; thanks for all the info.
I guess the least I can do is pull the head right away, though from what I'm hearing that won't necessarily provide the information that I need.
hmmm . . . questions, questions !

Jim