a couple of questions on head removal - PeachParts Mercedes-Benz Forum

MarkM · #1 02-09-2002, 10:24 AM

I read through the MBZ shop manual (for 1985 300D...123) regarding removal and replacement of head, and it all looks very easy. Since when I remove the head, I want to do a valve job, and down time is an important factor for me, I will probably buy a rebuilt head and just switch them. I would like to remove head on a Sat. and install the new one on Sunday. Hopefully I will have obtained all parts needed...new head bolts, gaskets for head, manifolds, turbo, etc., new seals for injectors, etc. I will also replace oil filter housing gasket at this time.

1) Is two days enough time for this? (I will probably take Friday off and start then.)

2) After detaching all accessories (just prior to lifting off the head) the MBZ manual says to detach the cam sprocket and slide rail, then lift off head. Am I correct in my understanding that it is not necessary to grind off a link in the timing chain and separate the chain?? Instead, it appears that the chain remains intact, and the sprocket and slide rail stays in place as you lift off the head. Is this correct? (my timing chain is new)

3) The screw for the slide rail needs to be removed by a special tool...threaded shaft with slide impct puller....it seems that this tool could easily be shop-made using the appropriate size bolt attached to the tip of a slide hammer ...I could weld a proper metric bolt to a threaded rod and make my own slide hammer. I that all that is involved??

4) Do I need a hoist to lift off and replace the head??? I assume it weighs about 75 pounds? Anyone done this using elbow grease alone??

Thanks

psfred · #2 02-09-2002, 11:20 AM

Mark:

If you are beefy and used to lifting large weights at odd angles, you can get the head off yourself. If you are NOT used to lifting large chunks of steel, bales of hay, etc, get a helper. I'ts a long reach, and back spasms will definitely make the job take longer.

The bolt pin can be pulled using a bolt and a pile of washers or a socket -- you don't need a slide hammer.

Wire the chain to the cam sproket, then use some stiff wire (brazing rod or flat silver solder sticks are what we use) to slide under the head and through the chain when you get the head loose. It is somewhat important that the chain stay tight on the lower part. You will need to wire it up and hold it taut while exchanging the heads, another reason for having a helper.

Check your chain stretch before you start -- a new chain, if necessary, isn't that big a deal to put in.

Peter

tcane · #3 02-09-2002, 01:05 PM

Mark:

Two days is more than enough time to R&R the head as long as you have all parts/tools needed and nothing unusual happens.

You do not have to break the timing chain to remove the head. The guide rail has to be removed because the chain runs through it. Also, your timing chain tensioner is the ratcheting-type and it will be a lot easier to remove it so the tensioner rail/chain guide will have enough slack to let the timing chain move around (you do not need to remove the tensioner rail/chain guide). However, I was not able to remove the head with the camshaft sprocket attached to the chain because the timing chain idler gear was in the way. So, I removed the cam sprocket from the timing chain. I rotated the engine so the timing marks on the crankshaft and camshaft lined up at TDC on #1 cylinder on the compression stroke, used some paint to mark the timing chain and sprocket, removed the cam sprocket and kept tension on it while attaching a coat hanger to it so I could tie the coat hanger to the mount for the cruise control and keep tension on the chain while removing other parts, put the cam sprocket bolt and washer back into the camshaft finger tight to keep the camshaft from moving out of the cam bearings/towers (and/or you can use small diameter wire or string to tie the camshaft to one of the cam bearing/tower to keep it from moving).

I used an engine hoist to remove the head because it weighs about 100 pounds, the brass injection ports extend beyond the head and are not protected so you should not drag the head across anything to prevent damaging them (it is an awkward position to just try and grab the head from over the fender or in front over the radiator to try and remove it) and I could not stand in the engine compartment to lift the head straight up to remove it (but maybe you can). If you have help, then two people can probably remove and install the head without a hoist. Also, when installing the head an engine hoist makes it a lot easier to position the head and avoid damaging the new head gasket, snake the timing chain up to re-attach it, etc., etc. Also, I used a stretch cord on the timing chain (after removing the coat hanger, which was the first thing I thought of to hold the timing chain) attached the stretch cord to the engine hoist to keep tension on the chain as I removed the head, once the head was up high enough I removed the stretch cord from the engine hoist and moved the timing chain/stretch cord through the head and secured the stretch cord to keep tension on the chain.

Of course, you can just drop the timing chain (after removing the cam sprocket and attaching a piece of coat hanger wire to the chain) into the engine block and then re-time everything and prevent/hope the injection pump does not move so that you do not lose timing (and before mounting/ closing everything you absolutely must check start of delivery of the IP to make sure it is timed correctly - a one tooth mis-position equals 18 degrees - and it is a lot easier to move the timing chain when you have easy access).

You can rent an engine hoist from several local rental places for about $20/day, look for a light-weight hoist that breaks down into easy to handle pieces that can be loaded into a trunk, pick-up bed, etc. ( I put one into a Hyndai hatchback).

I made a tool to remove the rail pins using a 14mm deep socket (the inside diameter needs to be large enough so the pin will not contact the inner walls of the socket, the rail pin has a 10mm head diameter), a long 6mm dia. x 1.00 thread pitch bolt that is about 1/2" longer than the socket you use, 8-10 flat washers (3-4 washers with the same inside diameter as the 6mm bolt and several washers with larger inside diameters), clean the rail pin threads real good, insert the bolt through the socket with one 6mm flat washer and perhaps one larger diameter flat washer, thread the 6mm bolt into the rail pin, use the appropriate sized wrench to turn the 6mm bolt (probably 10mm), there will be some force needed to break the rail pin free, tighten the bolt until it cannot be tighened further (but do not force the bolt tight because you will need to loosen it), remove the 6mm bolt and add 1-2 flat washers and re-thread the 6mm bolt into the rail pin and tighten the bolt until it will not go any further, remove the 6mm bolt and add more flat washers, etc., etc. until the rail pin comes completely free. When instaling the rail pin used Permatex silicone on the pin, thread the 6mm bolt into the rail pin, line up the mount hole on the timing chain rail guide to the hole in the head, insert the pin through the head through the rail guide, use a hammer to tap on the 6mm bolt and drive the pin home (you do not need to seat the pin with a lot of force, just enough to just seat the pin into position and no more), and wipe off the excess silicone leaving some around the outer edge of the rail pin head.

Make sure to clean off all the old gasket material (I use very sharp wood chisels and a brass brush to polish the mating surfaces) avoiding getting any old gasket into the block and isopropyl alcohol is good for removing oil/grease to clean the gasket mating surfaces so the new gaskets will adhere properly and seal. The head bolts and engine block should have a tap and die run through them to ensure the threads are clean and proper torque can be achieved. Measure the head torque-to-yield bolts to make sure they can be re-used. Use a bit of oil on the threads (not too much since the holes are closed and too much oil can prevent the bolts from threading all the way down) and oil on the bolt headsand washers where they contact each other and where the washers contact the head and cam bearing/tower).

The oil filter cannister housing gasket should be the thick one (not the paper-thin one my engine had on it). If you use silicone on this gasket (which I strongly advise against using) then use a very small amount because the squeeze out/excess silicone can get into the oil beyond the oil filter and this goes straight to the main crankshaft bearings and/ or the big-end connecting rod bearings and can/will cause serious damage (I've seen this happen on other than M-B engines and there is an old post talking about a broken M-B crankshaft caused by excess silicone from the oil filter cannister gasket replacement getting into the oil passage way to the crank). I used a bit of grease to soften the cannister gasket when mounting mine and the grease helps hold the gasket in place. Also, some of the 6mm Allen head bolts holding the oil cannister are hard to reach. You will need the Allen head wrench that is just the the hex metal bent at a 90 degree angle for at least the one bolt in the middle of the cannister and it helps to also have the type that has a socket attached to the hex portion for the other bolts. Make sure the old gasket material does not get into the oil passages. Also, when removing the oil pressure line from the cannister be aware you may have the type of pressure line that has a fitting that will not loosen at the cannister, meaning that the oil pressure line will need to be removed from the oil gauge in the dash (I have had two oil pressure lines that would not loosen at the cannister - hopefully yours will loosen at the cannister, but if not . . .).

My $0.02 worth, and I am sure other member(s) will have their comments/suggestions.

Good Luck!
Tom

P.S. Fred makes a good point to check your timing chain for stretch. I wrote in another thread the proper way to check for chain stretch, so look in my old posts for the info and specs.

MarkM · #4 02-09-2002, 02:58 PM

Peter & Tom,

Thanks a lot for excellent information. I didnt think of RENTING a hoist...I will definitely do this....my back is not what it used to be, and I'd hate like hell to damage something when putting in the new head!!!

Since this job must be done over a weekend, I think I will just buy all new head bolts...although maybe not if they are $10 each??

I will print out your responses, and start a file to plan for this....this will be my first time removing a head!

Thanks again.

Mark

TimFreeh · #5 02-09-2002, 03:41 PM

Head bolts (at the MB dealer) are $5 per copy. The longest ones are the ones that stretch most often, I had to replace about 8 of the bolts when I had my head off.

It's not a bad job - 2 days should be plenty of time.

engatwork · #6 02-09-2002, 04:51 PM

2 days sounds about right. The only curse of working on anything other than a Chevy or Ford is getting it ready to put together on a Sunday and not being able to get a part. Plan your work out and you will not run into this problem. I pulled the head on the 240D without a hoist (I was sitting on the passenger side fender but I am planning on using the hoist on the 300D head). I agree with tcane - the cam shaft sprocket has got to be taken out of the way so make sure you mark the chain/sprocket relationship. It will be easier if you have a friend there when you remove the head to help out with keeping tension on the chain in the lower end. Back the tensioner off before removing the cam sprocket.

MarkM · #7 02-09-2002, 07:11 PM

Instead of taking friday off, I should start the job on Saturday and plan on taking Monday if needed.

I like Peter's suggestion about keeping tension on the timing chain...lifting the head slightly, then sliding a stiff piece of metal under the head and through both sides of the chain..a piece of flat brazing rod or a small piece of 3/16" bar stock from Home Depot would work just fine.

I think I see about removing the cam gear...I do need to remove the chain tensioner thereby providing enough slack so I can slip the chain off the cam gear after detaching it from the shaft. Thats why the MBZ manual, as well as you folks, indicate the need to mark the position of the chain on the cam gear.

Another thing, the reconditioned head will likely have been refaced...thus I would need to set start of delivery. I did this once and could not loosen the bracked at the back end of the IP...at the time I only needed to move the IP slightly..and I could do this with a pry bar and just bend the support bracket. This time I may actually need to move the IP more....any hints on getting at the rear IP support bracket ( I have the drip tube and know how to do the rest).

Thanks again,

Mark

gsxr · #8 02-09-2002, 08:07 PM

Tim,

Head bolts through mail order sources (FastLane, Wholesale Parts, etc) are much cheaper. I got mine (for my impending OM603 head gasket job) for $1.80-$2.20 each. Rather than dink around with measuring all the bolts, or taking a chance on marginal ones, I ordered all of them - cost about $50 but I figure that's relatively cheap insurance, since I don't EVER want to do this job again!

Regards,

psfred · #9 02-09-2002, 08:28 PM

Mark:

Replacing the head will not alter the injection timing unless the chain slips on the injection timer, which will not happen unless you remove the retainer bolt on the side.

Most likely the head won't have been resurfaced, either, as they don't warp, as a rule -- cast iron rather than aluminum.

Jim:

How's the 240 running now? I just got the 220D started again -- stuck tumbler. I've ordered a new one, just have to figure out how to get the face off the old one now. I'm going to take a look at the vacuum pump, too -- I've decided it may have a hole in it -- blows blue smoke at idle all the time.

PEter

tcane · #10 02-09-2002, 10:13 PM

Mark:

The IP has a bolt with a 13mm head that supports the back end. Loosen the 13mm head bolt to allow the IP to move to adjust the start of delivery. You do not need to loosen the IP rear support bracket at the engine block. The best way to reach this bolt is between the oil cooler lines using a ratchet head wrench made by Gear Wrench (a combo ratchet head and open end wrench). You can buy the Gear Wrench at O'Reilly's Auto Parts or Ace Hardware - either the 13mm or the 1/2" Gear Wrench will work.

I have a 300D head on my bench right now and the camshaft gear will not fit through the opening in the head with the timing chain idler gear in place (M-B uses the same cam gear for the 240D and both 300D's - turbo and non). The only way to leave the timing chain and cam gear connected is to remove the idler gear - a PIA and should be avoided, but you can do what you want to do. The idler gear interference is why I used stretch cords to keep tension on the timing chain (I had to remove the cam gear) since I was doing this by myself. There is a chance the timing chain can skip a tooth on the crankshaft gear - so keeping tension on the chain at all times will help avoid this (I did have the chain skip a tooth on the cranshaft gear, but I was able to fiddle the chain to skip one tooth to regain timing).

Planning on taking Monday off sounds like a good idea in case something happens and you need parts.

Good Luck!
Tom

RunningTooHot · #11 02-11-2002, 03:47 AM

I replaced my head recently -- you have received good advice in the above postings.

Personally I think that two days to do this job is probably pushing it a bit, unless you have done it before. I could do it in two days now that I have done the job previously. Familiarity with a job speeds things up significantly, so if this is the first time you're pulling a head on this type engine/car you may want to allocate a bit more time. The idea of taking Monday off for potential parts running & finishing up is a good one. I'd go one better and actually get cracking on it Friday after work -- the more time you have the better.

Getting the old head gasket material completely off of the block is critically important, but not easy. Permatex makes a spray on gasket remover that helps to dissolve the old gasket, which then makes it easier to scrape & brush away the residue. As suggested above, isopropyl alcohol is good however I use brake cleaner as a final cleaning solvent. Carburetor cleaner can be used for *initial* cleanup, but the brake cleaner leaves absolutely no residue.

I timed the injection pump while the head was off. Access to the bolts was much easier, and turning the crankshaft in precise increments is a breeze. Just keep tension on the timing chain to keep the crank gear & pump gear in phase. (And turn the crankshaft only in the proper direction.)

You are making a substantial investment in time in dollars, so I am assuming that you're planning to keep your car for a long time. While you have your head off, in my opinion, it is a good time to spend a few extra dollars to install some preventative replacement parts. A good idea would be to replace all of the small coolant/heater hoses. You may want to consider doing the oil cooler lines if they are original as well. Access to the right hand engine mount & engine shock is greatly improved with the turbo off the car. If your front crankshaft seal is weeping at all, this is the time to do it.

Good luck and let us know how things are going.

RTH

#12 02-11-2002, 07:07 AM

This engine does NOT have a ratcheting tensioner.

If the head has never been off before, you should be safe reusing the head bolts, I'm assuming you know to angle torque them. You can measure the headbolts if the head has been off before, or if you're not sure. As long as they're not stretched beyound spec, reusing them is no problem.

Two days should be plenty of time as long as you have the replacement head ready to go back on.

Good luck,

tcane · #13 02-11-2002, 11:34 AM

According to the M-B CD engine manual the 1985 300D turbo engine has a detent-type chain tensioner (OK, I called it a ratcheting-type but it means the same thing - the plunger increases chain tension as parts wear and is prevented from loosening with a detent mechanism). Perhaps Larry knows something about the type of chain tensioner in Mark's engine that others do not know and the M-B manual is wrong (not unusual, I've found mistakes in the M-B manuals and most other service manuals from all manuf.). If it is the older style chain tensioner, then Mark will have an easier time removing the head since the older type chain tensioner does not need to be removed to R&R the head since the plunger can be compressed to free the tensoiner rail a bit and allow the timing chain more slack. If it is the detent-type chain tensioner, then R&R'ing the head is easier if the tensioner is removed so the tensioner rail is not tensioned and the chain will have more slack.

Paint remover can also be used to remove old gasket material if there is a lot stuck to the mating surfaces - I've used Stripeze for years (spelling may be wrong) on aluminum and cast iron. Paint remover has a plus since it can be brushed onto the old gasket and not sprayed on which can get into places where it is not wanted. I've had 4 300D heads off of different engines and only minimal amounts of head gasket material was stuck to the mating surfaces and what was stuck scraped off easily (I've had some types of head gaskets split almost evenly with gasket material nearly welded to both the head and block because the manuf. used a really good adhesive - meaning the use of paint stripper made it a lot easier to remove the old gasket, in fact a necessity).

My, very cheap, $0.02 worth!
Tom

MarkM · #14 02-13-2002, 09:06 AM

Thanks again to all. The little details and hints are invaluable in preparing for the job...as each person as offered additional advice, I have created a file of info., and put together my shopping list. Tom, I bought one of those "Gear Wrench" 13mm racheting wrenches for adjusting the IP from Ace Hardware...these are very nice and high quality...especially nice is the 5 degree ratcheting increment....I think Ill buy myself a few more (a 10, 12 and 17mm....very usefull for this car).

I am expecting to keep the car for a long time, and have already done many, many repairs, including completely rebuilt AC (R134), suspension, new rear trailing arm, new axles, SS exaust, cruise as well as many other things.

RTH, engine mounts and shock were done within the past couple of years, and front seal leaks no oil. I do think I will do all the coolant hoses, as you suggest, since they are all original. You also suggested replacing the oil cooler lines...do you mean the ones connected to oil filter housing? I will be doing the gasket for the oil filter housing...but I'm worried about disconnecting oil cooler lines (maybe I need to anyway) because Im afraid they may be siezed and will strip aluminum threads.

I think I will also replace the fan clutch...the one in there is original (17 years old), as well as belts.

I plan on doing the job in a month or so when the weather warms up (since I will be in my driveway

). I will keep you informed regarding progress of the work.

thanks again,

Mark

tcane · #15 02-13-2002, 11:43 AM

Mark:

I like the Gear Wrench also - I bought the Snap-On ratcheting wrenches when they were first made and although they work great (very strong) they are a bit large to fit into some tight places and the ratchet gears are course also making them unuseable in tight places. The one Sanp-On ratcheting wrench that I've used a lot is a small one (5/16" x 1/4") that I can use either a Phillips head or slotted screw bit with - works great in those tight places where a short stubby screwdriver will not fit into or if the stubby does fit I can't get enough force on it to R&R the fastener (a Yankee works well also - it is a stubby ratchet with two sizes of slotted screw biu on it - plus I have several other 90 degree screwdrivers).

The oil cooler lines can be a real bear to remove, especially if they have not been removed before. You will see that there is fitting that screws into the oil cannister that the cooler lines then screw into. You may need a thin wrench on the fitting to prevent the fitting from turning (failing that then you may need to remove the cooler lines at the oil cooler and the holding clamp by the fuel pump and then unscrew the cooler line with the fitting still attached, then clamp the fitting into a vise to loosen it from the cooler line). I had to use a 15" adjustable wrench on the cooler lines and it took a lot of force to loosen them.

The AC lines can be rebuilt for a fraction of the cost compared to new lines. There should be at least one AC supply/repair business in your area that can replace the hose part that attaches to the metal part of the AC lines. I paid about $40-$45 total to have both of my AC lines rebuilt with hose that was better than the M-B AC hose. Hydraulic lines (oil cooler, power steering, etc.) can also be rebuilt at heavy equipment or hydraulic supply/repair shops also for a fraction of the cost of new lines. Call around to find these places.

Inspect your trans oil cooler lines for condition. These can be bought cheap at Fast Lane. I'm just now replacing mine, but they are still in good condition without leaks. Cheap insurance against ruining the trans.

My fan clutch is older than yours and still works as it should. You can check yours for correct operation and if it is OK then you can save that $ for something else. The ones that I've looked at all leak a bit of oil and that oil is covered with dirt - they look worse than they really are. One thing to keep in mind when removing the fan clutch is to keep it in an upright position so the oil does not run out - so don't lay it on its side for any length of time (a few minutes is OK as you're removing things and your hands may be full and/or you've gotten into a hard to achieve position to work).

Good Luck!
Tom

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