M104 e320 engine questions

[DieselJim]

Got my used engine off the pallet and looked at it. I guess its in ok condition. Shows some corrosion from being from a northern car for almost 20 years.

1. Some debris in intake ports. Thinking of just taking the shop vac and sucking that stuff out. I can see the valves but I assume that it won't hurt anything to shop vac the intake ports.

2. Looks like the rear crankshaft seal is indeed leaking on the used engine. Definitely going to renew it. Is there a mainstream solution to those star shaped bolt heads or do I need an oem tool?

[Aquaticedge]

shouldnt hurt to suck the debris out. be careful around the valves though. while the engine is out, redo any of the seals in the back of the engine while you have access to them

[slk230red]

Originally Posted by DieselJim

Is there a mainstream solution to those star shaped bolt heads or do I need an oem tool?

NAPA should have the tool you need to remove the head bolts. I bought mine there when I removed the head on my W201.

[engatwork]

Is there a mainstream solution to those star shaped bolt heads or do I need an oem tool?

They are torx fasteners. You should be able to purchase the proper sockets at NAPA.

[TheDon]

I used the harbor freight torx drivers to remove the torx fasteners from my cabrio.

[DieselJim]

Originally Posted by engatwork

They are torx fasteners. You should be able to purchase the proper sockets at NAPA.

Yeah I have a torx set for torx screws. I'll find a torx socket for a bolt head. Back to harbor freight. I need to replace those bolts?

[DieselJim]

Can I just get the impact set at HF and pop those babies off with an impact wrench?

[DieselJim]

Ok. I need a wrench for these funky stretch bolts. I also now understand the torque spec. fun

[97 SL320]

Before this thread drifts too far.
What bolts do you want to remove? It sounds like you want to remove the flywheel / flex plate.

From the pics that I have of a 104, the flywheel to crankshaft bolts are torx that require a " T " bit. ( the socket version is " E " ) I think there is a revised torx shape out there but I don't think that existed until the past 8 years or so.

Impacts on a torx are a bad idea, they are not so strong due to limited size relative to the thread and head / washer diameter.

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New info

I took a look at a actual 104 I have, the FW bolts are 12 point not torx like the ones in the picture I have. A regular 12 socket will do the trick.


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To make things easier, hit the bolt head directly with a hammer to slightly imprint the bolt head into the surface. Doing so breaks the "stiction " and slightly reduces tension on the bolt. Use a t handle breaker bar, with the bar centered, this allows you to apply the torque evenly preventing the bit from caming out of the bolt. This is critical with stuck bolts, pulling on one side wedges the bolt to one side increasing friction.

As for stretch bolts, ( torque to yield ) no special tools are required other than a regular torque wrentch for preload. Marking the bolt head for degrees, looking at the angle of the ratchet is usually enough. I preload TTY bolts to a torque wrentch then angles by eye and feel. Once you feel the torque level off, turning more does not make the bolt tighter because it is stretching.

[97 SL320]

I've got more information, see edited post above.

[DieselJim]

Have to break out my old 12 point sockets. I use my nicer six point set almost exclusively these days. I played with the impact wrench doing a brake job on the mini van and will do my 300d's brakes before getting back to the engine job. Thanks for the ideas. Seals were definitely the big thing I didn't think of

[DieselJim]

So which is better the stretch bolt or the torx bolt?

[97 SL320]

Better for what?

A stretch bolt ( Torque to yield ) is used when maximum clamping force is needed. Torque readings only infer clamping force and can be affected by thread friction. Head shape can be anything.

Torx only refers to the type of head. These are typically where space is a issue / tamper resistance is needed. Allen bolts used to be used in these apps but have limited resistance to stripping the head. The torx spline shape took care of this.

[DieselJim]

Well it appears there is an internal torx head bolt that replaced the stretch bolts in 1995. I wondered if I should favor one or the other to put the flywheel back on with.