75 240D Head gasket, I need some input...
 

Okay,
I have to admit I am deeper than I have ever been into a motor. Can you believe it after almost 50 years of tinkering on cars this is the first head I've pulled.

So here's my question:
The rear of the head was leaking a little water due to a blown gasket. The mating surfaces are showing a little corrosion around this area (no pitting though) that appeas to be just surface buildup. To clean this can I just take a wire wheel on my drill motor and have at it? Can I use this to clean up both mating surfaces before reinstalling the new gasket and head?

Also I thought I might make a deal with my local tranny shop and have him run the head through his parts washer but will this hurt anything? I have not pulled the valves so the seals and everything are still in the head.
Will these be damaged by the washing?

2nd question, I am preparing to place an order with Phil and I'm in debate about the valves and seals as this car has never used a drop of oil and I mean after 1100 hard miles on the freeway it was not down a drop. I have not seen any usage even between oil changes so I guess I have to question whether or not to mess with the valves and seals. Thoughts?

Whats the miles on that 240D???

Instead of going to tranny shop, why dont you take the head to machine shop that can also wiggle the valves in their guides to check for excessive play and measure the head for warpage, spotting tiny cracks or anything else that might be wrong with it.

But whatever you do - dont let em shave or plane the head beyond MB specs, if at all... this can bump the compression beyond tolerances and soon blow the engine if they remove too much metal from surface area.

On cleaning surface contact areas of both head and block I've always used 220 grit sandpaper.... i dunno about steel brush wheel. I think valve guide seals come with the complete head gasket kit, so you might as well have the shop install them too.

Better let the machine shop itself order whatever guides you are haggling with Phil about... they come in standard size and oversize that can only be measured with machine shop calipres to fit worn valve stems.

Damned easy... pulling the cyl head on 240D, isnt it? And dont forget new manifold locknuts when you get back to Phil.

What's the total milage on the car? 150,000 or up, I'd look at the valves while it was out.

Do not run an assembled head through any cleaning system, you will likely ruin the valve guides. If you want to tank it, you will have to remove the valves.

If it were me, I'd just pull, clean up, and re-install. If you don't have any oil consumption, you don't need to do the valves unless it is really hard to start. Most likely, if you have no oil consumption, the valves are fine.

When you go to pull the head, wire tie the chain to the cam gear and then remove the head bolts. Remove cam gear, then break head loose while someone else holds the gear. Lift head some and shove some wire through the gap between head and block up front to trap the chain.

I belive you must also remove the upper chain guide (driver's side) and possibly the tensioner and tensioner guide rail (bent steel one, plastic one can stay in).

Peter

Fisherman

If you can detect any "wiggle" of the valves you should replace the valve guides, then you must do a valve grinding job. I borrowed the valve grinding tools from a friend and did it myself, not a big deal, (first time for me too) then replace the seals. I was shown how to do things along the way and what I was told when I said "think i will just take it in", was "doing the valves is ONE job you can do yourself and it will be fun" If you have a friend that can help you get started and has the grinding tools, go for it. If your valves are snug in the guides, lap the valves, then have it hot tanked, new seals, and your back on the road. You might consider having the head magnafluxed for cracks, they clean it up then. Anyway it was worth it for me to learn how a valve job is done even tho I am still doing stuff for my friend to pay off the trade for the lessons. The parts in a valve job, guides and seals are really cheap. Its winter, no fishing anyway.;)

Thanks
 

Yeah, I pulled the sprocket and the chain together although i am putting in a new chain cuz, heck I'm there and it shows about 4 degrees stretch by just aligning the timing marks.
I think you're right about the valves being okay. I just needed a nudge over the edge to feel a little more confident. I think the guides are fine it is the seals I was going to throw in since they are cheap and easy when the ehad is off the car...:)
I'll loosen the valves and give a visual to the seats and tops but all in all this car has run really good.
I was debating the machine chop but everyone around here is pretty pricey and frankly I am not going to get much for the car in the long haul. Mommy likes the 5 cylinder power (if you call it that when N/A).
The big bonus is how much room there is now to change out the starter...;) The bearings are going bad and it spins up a little slow. I have a friend who is selling me his starter out of a 79 300 for cheap. Figured I may as well change it over.
BTW the car has about 240,000 on it.
Thanks for the input.

DO NOT clean the head or block with abrasives with the pistons in the engine!!!!

Loose abrasive (even from Scotchbrite pads) ends up on the compression ring and will rapidly eat the cylinder walls.

Use solvent and a blunt scraper to clean the surfaces.

Please.

Peter

good point, Peter
 

even after plugging the holes though? I figured to tape off the cylinders and then not throw stuff all over but maybe you're right... I just have some scale from where the water has been seeping by the back of the block and I don't think a scraper is going to get it off.

When I scrape I get the shop vac out and put on my ear protection and hold the vac tube in one hand and scrape with the other...

Good plan also...
 

Greg,
You would be impressed... I had the cahnce to look over a used head opff a 79 300D just for planning purposes on this projeect and guess what. Two of the prechambers are burnt all the way through on the tips.
Hmmmm, think that could be a problem on my 300????
I'm gonna build that tool to pull them this weekend and see.

Great, I hope you take pictures of your tool making process.. you know I have been wanting an excuse to do this to mine too.... LOL... it still feels like you and I are the only ones that appreciate the potential problems of a bad precombustion chamber....

Greg

So what woulda caused those precombustion chamber tips to burn off, bad spray pattern, using ether, sun spots, what?

I wonder what the chances of a problem with precombustion chambers is if the holes are not plugged and the tips look good.

Bad injectors shooting a solid stream of fuel rather than an atomized mist. They can burn through the prechamber on the side, too, if spray sideways.

Busted ball pin could do the same, I think.

Excessive oil burning from a bad vac pump will also burn the prechambers.

Peter

thanks Peter

Seems it would be running real bad and/or smoking, to give a "heads-up" that sometinng was wrong.:eek:

Steve

Thanks Peter, I was going to go for the sunspots....you saved me....:D

My symptoms...
 

I have a slight miss in one cylinder. I know it is not a full miss (you would really feel that) but I have been chasing this down for almost a year.
1st thing I did was change over IPs as I had another handy. No change.
I then pulled the Injectors and had them tested, they were all relatively fine.
When pulling injectros though I noted that my number two seal ring was almost burnt through aruond the bottm of th einjector...
That'swhen I started consideringthis issue.
I'll let ya all know what I dfind if I get to it this weekend.