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Pelican Technical Article:

Head Gasket Replacement

Steve Vernon

Time:

14 hours14 hrs

Tab:

$140 to $1,000

Talent:

*****

Tools:

All of them

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

New head gasket set and head bolts

Hot Tip:

Get a friend and a hoist to help you lift the head

Performance Gain:

Longer engine life

Complementary Modification:

Flush your cooling system and replace your radiator hoses

There are several signs that you are in need of a new head gasket. The most common amongst them is the mixing of your oil and coolant. If you have had a water pump or thermostat fail, and your car overheated, there is a very good chance you are going to be looking at performing this job, as the extreme temperatures associated with an over heated engine can damage both the head and its gasket. Our project car had a catastrophic head gasket failure that lead to serious cross contamination of the oil and coolant.

Replacing your head gasket might be the biggest job you will attempt on your car short of rebuilding the entire engine. It is not a quick or easy job, but can be done by a DIY mechanic if you take your time, have the right tools and follow the instructions. This job can take a few days for a novice, so make sure you have the car in a secure and weather safe area before you start. You are going to be opening up the engine and may even be sending the head out for repairs, so you don't want to be working outside when it starts to rain.

I can not stress this enough: get a digital camera and take lots of pictures before and during this job. Document wire and vacuum routing plus anything you feel unsure of. This can only help when it comes time to put everything back together.

There are several steps that need to be performed on other parts of the car before you begin removing the cylinder head. We have covered all of these in separate articles so I am not going to include them here, as this will be a long enough project as it is. Please refer to all the other articles in the order they are listed and then return here.

First, safely raise and support your vehicle. Drain the cooling system. Remove the fan and drive belt.

There are three ways you can remove the head: with the exhaust and intake on, with the exhaust off and with both the exhaust and intake off the head. We are going to show you how to remove the head with the exhaust and intake systems removed. I find this to be the easiest way and gives you an opportunity to go through each system: the hoses, lines and fasteners and inspect each piece as you go. You don't want to go through all this work to get lousy results because you missed a failing vacuum line.

The head is extremely heavy and needs to be pulled straight up off the block as well as reinstalled precisely. I highly recommend using an engine hoist to remove it from the car. You run a serious risk of hurting yourself and the car by trying to lift the head from the engine without some form of mechanical lift.

Meticulously clean the head and the mounting surface on the block. Run a tap down each bolt hole on the engine deck. Then tape a large straw into the end of a ShopVac to suck out any liquid and trash. This cleans the threads and prevents hydraulic pressure from breaking the block or giving false bolt torque when installing the cylinder head. Sit the new gasket over the locating dowel pins and reinstall everything. Make sure you follow the bolt pattern for installation and torque to the specs on your engine. Mercedes-Benz usually will give an initial torque spec and then following the tightening pattern ask you to tighten all the bolts an additional 90 degrees twice. Note: for best results wait fifteen minutes between 90 degree torques. Make sure you double check your torque settings before starting.

Once everything is reconnected and buttoned up, it is a good idea to change the oil and add fresh coolant.

The following pictures are taken from the articles you will need to reference for work needed before removing the cylinder head.

Disconnect the negative or ground cable from the battery.
Figure 1

Disconnect the negative or ground cable from the battery. Please see our article on battery replacement.

Drain the coolant.
Figure 2

Drain the coolant. Please see our article on coolant flush and replacement.

If your coolant looks like this (red arrow) you have a serious coolant oil mix.
Figure 3

If your coolant looks like this (red arrow) you have a serious coolant oil mix.

Remove the fan and shroud.
Figure 4

Remove the fan and shroud. Please see our article on fan and shroud removal.

Remove the coolant hose along the front of the motor.
Figure 5

Remove the coolant hose along the front of the motor. Please see our article on coolant hose replacement.

Remove the air filter and box.
Figure 6

Remove the air filter and box. Please see our article on air filter removal.

Remove the air cross over pipe and MAF sensor.
Figure 7

Remove the air cross over pipe and MAF sensor. Please see our article on air cross over pipe removal.

Remove the resonance valve.
Figure 8

Remove the resonance valve. Please see our article on resonance valve removal.

Remove the throttle body.
Figure 9

Remove the throttle body. Please see our article on throttle body removal.

Remove the spark plugs and wires.
Figure 10

Remove the spark plugs and wires. Please see our article on spark plug and wire removal.

Remove the fuel injectors and fuel rail.
Figure 11

Remove the fuel injectors and fuel rail. Please see our article on fuel injector removal.

Remove the intake manifold.
Figure 12

Remove the intake manifold. Please see our article on intake manifold removal.

Remove the valve cover.
Figure 13

Remove the valve cover. Please see our article on valve cover removal.

Remove the exhaust manifolds, EGR and air pump tubes.
Figure 14

Remove the exhaust manifolds, EGR and air pump tubes. Please see our article on exhaust gasket replacement.

Set the engine at Top Dead Center (TDC).
Figure 15

Set the engine at Top Dead Center (TDC). Please see our article on setting your motor at TDC.

Remove the two 10mm bolts for the cross over valve (red arrows), the electrical connection of the air pump (green arrow) and route the vacuum and electrical lines away from the front of the head.
Figure 16

Remove the two 10mm bolts for the cross over valve (red arrows), the electrical connection of the air pump (green arrow) and route the vacuum and electrical lines away from the front of the head.

Use a 6mm Allen and remove the lifting bracket from the front of the head (red arrows).
Figure 17

Use a 6mm Allen and remove the lifting bracket from the front of the head (red arrows).

': Remove the two 5mm Allen bolts and the camshaft positioning sensor from the front left side of the head.
Figure 18

': Remove the two 5mm Allen bolts and the camshaft positioning sensor from the front left side of the head.

': Use a 5mm Allen and remove the variable cam adjuster on the front of the head (red arrows).
Figure 19

': Use a 5mm Allen and remove the variable cam adjuster on the front of the head (red arrows). Disconnect the wiring connection (yellow arrow) and remove the adjuster from the head.

Remove the six 13mm bolts holding the timing chain cover to the front of the head (red arrows).
Figure 20

Remove the six 13mm bolts holding the timing chain cover to the front of the head (red arrows).

The bolts are different lengths.
Figure 21

The bolts are different lengths. I like to drawn a quick diagram on an old cardboard box and stick the bolts into it in the order they are removed (red arrow). It makes it much easier when you go to reinstall them.

Gently pull the timing chain cover away from the head (red arrow).
Figure 22

Gently pull the timing chain cover away from the head (red arrow). You may need to give it a few gentle taps with a rubber mallet to get it to separate. DO NOT pry a screwdriver between the cover and the head. Remove the chain guide from between the two cams (yellow arrow).

You need to get access to the chain tensioner.
Figure 23

You need to get access to the chain tensioner. Remove the two 15mm bolts and remove the air pump. You can just remove the top bolt and swing the air pump out of the way if you want.

To loosen and remove the chain tensioner, first use a 10mm Allen and loosen the inner bolt one full turn (red arrow).
Figure 24

To loosen and remove the chain tensioner, first use a 10mm Allen and loosen the inner bolt one full turn (red arrow).

With the inner bolt loosened use a 27mm socket and remove the second bolt (red arrow).
Figure 25

With the inner bolt loosened use a 27mm socket and remove the second bolt (red arrow).

Remove the tensioner from the engine (red arrow).
Figure 26

Remove the tensioner from the engine (red arrow). This will allow the timing chains to loosen and give them slack.

Remove the three T40 Torx screws holding the exhaust sprocket to the cam (red arrow).
Figure 27

Remove the three T40 Torx screws holding the exhaust sprocket to the cam (red arrow). You can mark the sprocket and chain, but seeing as how you are sending the head out for inspection, cleaning and repair you will need to retime the engine.

Use Mercedes-Benz tool #116 589 20 33 00 and remove the guide pin for the intake chain rail (red arrow).
Figure 28

Use Mercedes-Benz tool #116 589 20 33 00 and remove the guide pin for the intake chain rail (red arrow). This pin holds the guide rail to the head and must be removed to separate the head from the block. Slip the timing chain off the intake sprocket and tie it out of the way so it cannot slip down into the engine.

Disconnect the EGR tube bracket from the rear left side of the head (red arrow).
Figure 29

Disconnect the EGR tube bracket from the rear left side of the head (red arrow). Use a screwdriver and remove the hose clamp for the coolant line that exits the rear left side of the head. Remove the coolant hose from the head as well (yellow arrow).

Just like tightening the head you also need to loosen it in a specific order.
Figure 30

Just like tightening the head you also need to loosen it in a specific order. This photo illustrates the order in which you should loosen the head bolts. Start loosening with a ' turn on each bolt and work your way through the order until they are all loose.

When removing the torque bolts make absolutely sure you have the right socket and that it is seated correctly (red arrow).
Figure 31

When removing the torque bolts make absolutely sure you have the right socket and that it is seated correctly (red arrow). Our bolts needed a 12mm Triple Square. You absolutely do NOT want to strip these bolts.

Once all the bolts are loosened and removed (note you cannot remove the bolt on the rear left side of the head) attach a chain to the mounting bracket on the rear of the head and use a bolt into the mounting bracket hole on the front.
Figure 32

Once all the bolts are loosened and removed (note you cannot remove the bolt on the rear left side of the head) attach a chain to the mounting bracket on the rear of the head and use a bolt into the mounting bracket hole on the front. Attach the chain to an engine hoist and lift the head straight up. You will need to lift it up then a little forward to have it clear the firewall at the rear. Send the head out to have it cleaned and checked. These heads tend to warp and crack.

Remove the old gasket from the timing chain base (red arrow).
Figure 33

Remove the old gasket from the timing chain base (red arrow).

Remove the old head gasket (red arrow).
Figure 34

Remove the old head gasket (red arrow).

Remove the remains of the old gasket.
Figure 35

Remove the remains of the old gasket. Inspect the piston crowns and the cylinder walls. Carefully clean the mating surface. Run a tap down each bolt hole on the engine deck. Then tape a large straw into the end of a ShopVac to suck out any liquid and trash. This cleans the threads and prevents hydraulic pressure from breaking the block or giving false bolt torque when installing the cylinder head. There was nothing wrong with our car when I pulled the head so I did not need to rotate the engine while working on it. If you need to rotate the engine while working on it just remember you will need to set the crank and the valve train at TDC for reinstallation. Your witness marks will be useless once you move the crank or send the head out for work!

Make sure you follow the bolt pattern for installation and torque to the specs on your engine.
Figure 36

Make sure you follow the bolt pattern for installation and torque to the specs on your engine. Mercedes-Benz usually will give an initial torque spec and then following the tightening pattern ask you to tighten all the bolts an additional 90 degrees twice. Note: for best results wait fifteen minutes between 90 degree torques. Make sure you double check your torque settings before starting.

The only real difference in installation is the chain tensioner. With everything clean you will first install the chain tensioner housing into the bore and then screw in the threaded ring and torque to your engine's torque value. Next, insert the pressure pin with its detent spring into the assembled chain tensioner housing. Install the compression spring and screw plug and torque down. Don't forget to reinstall the rail guide pin. The rest of the installation is the reverse of removal.


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Comments and Suggestions:
quest1966 Comments: Regarding Figure 28 and Mercedes-Benz tool #116 589 20 33 00, rather than spend a couple hundred dollars, for $1.50 buy a 2-3 inch bolt, threaded to the head I think it is M6 orM8 a nut and a couple of washers one small enough to fit the bolt and a second one large enough to cover the top of a 1/4" socket.

1 Screw the nut most of the way to the head of the bolt.
2 Place the small washer on the bolt then the larger washer, then 1/4" drive socket with about 1" depth, as small as possible but larger than the guide pin.
3 Screw this assembly into the guide pin as far as possible.
4 Use wrench on the nut and another wrench or socket to hold the bolt head.
5 As you screw the nut toward the end of the bolt, the pin will pull out.

Hope this helps save a fellow DIYer some significant cash - no offense Pelican Parts. :
November 6, 2016
  Followup from the Pelican Staff: No offense. Love real world work flows. Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Doug Comments: Okay Nick, My vehicle is 95 e320 and I find alldata is pretty screwed up with missing information and incorrect diagrams. I cant reccomend them. And I replaced the head gasket which was leaking from corrosion between #3 and #4 cyl and also leaking oil at the #6 rear corner..Ran beautifully! but still smoked just as before! So again removing the head I discovered transmission fluid in the #3 and ??? found a bad vacuum modulator valve and clearly it was drawing trans fluid through the vacuum line into #3..smoked like crazy! I do find one mention of this issue on the Mercedes forums and now have a new valve on order hoping to install and adjust but find little detail on the procedures. Alldata does not even note the existence of the component at all..Hope this helps a reader looking into supposed head gasket issues with smoking!

If anyone has vacuum modulator adjustment instructions for the 94-95 124, e320...Im all ears. Hopefully the pressure gage adjustment while driving is not needed on this model as on the older ones and it can be driven and set by driveability tests..
June 10, 2016
  Followup from the Pelican Staff: Good catch. I have seen that happen on vacuum modulated transmissions. The correlation of the head gasket makes it tough to get sorted.

I recall being able to set it using shift points. If you can find the shift point data, you can adjust from there.- Nick at Pelican Parts
 
Doug Comments: so looking at the timing chain tensioner versus idler sprocket option to dissasemble I find nothing like the sprocket shown in my alldata instructions..and I remove the tensioner spring which is supposed to ratchet out and not compress again without releasing the trigger pin, but mine compresses again just fine..no release needed..There are variations! And I find that I already have the updated head gasket with reinforced corners. One bolt was loose..15 foot pounds or less..Still waiting on machine shop inspection report on the cylinder head..perfectly flat but exhaust valves looked pretty worn to me..Intake valves perfect and no oil consumption..We will see..
May 16, 2016
  Followup from the Pelican Staff: What vehicle do you have? I would like to have the article updated to reflect this info. - Nick at Pelican Parts  
Doug Comments: Glad its helpful! More notes...alldata gives the procedure to not remove the tensioner spring but instead take off the idler sprocket to release the timing chain. Its possible to destroy the chain my improperly replacing the tensioner so best leave it in..alldata also suggests removing head and manifilds as a unit..those lower manifold nuts are pretty rough access w head installed! Im now researching the issue of advisability of a valve job on a high mileage engine..waiting for the macinists report on condition of valves..the motor was running perfectly w no oil consumption.. Passed DEQ w wide margin...only issue was the head gasket failure..which seemed to be triggered by fixing a coolant leak...
May 14, 2016
  Followup from the Pelican Staff: Thanks again! - Nick at Pelican Parts  
Doug Comments: so the guide rail pin seems to be whaat is called a close tolerance part. The threads seem smaller, very tight but this is just close tolerance work..and the pin has an intereference fit where the hole is exactly equal to the pin size..pulls out with steady pressure from a nut threaded onto an engine 5mm against a spacer made of tools or hardware..
May 11, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Doug Comments: http://www.peachparts.com/Wikka/M104HeadGasket
Now here is a good article on this...very helpful.
May 11, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Doug Comments: The variable cam adjuster...need not come off. It occurs that if it can just be removed..you can just take the timing chain cover off with the adjuster on..yep. Just did it this way...now that pesky guide rail pin!
May 11, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Doug Comments: I an halfway through the job..found the hose clamps set up before the engine was installed and screw heads innaccesible. No big deal, chistled off the clamps and will replace them. But im confused why the instructinos say to remove the throttle body when the head can come off with it in place. Its not in the way..
May 10, 2016
  Followup from the Pelican Staff: Assuming it a method used by the author to keep the throttle housing safe. This is his technique, your experience may vary. - Nick at Pelican Parts  
vt Comments: The tool is mentioned under picture 28.
July 10, 2015
  Followup from the Pelican Staff: We can get you the tool:

Mercedes-Benz tool #116 589 20 33 00

Give our parts specialists a call at 1-888-280-7799- Nick at Pelican Parts
 
vt Comments: what is the tool that is 116589203300? May i find it in a regular store? I bought all the parts for the job but I dont think i have that tool. Thank you.
July 9, 2015
  Followup from the Pelican Staff: I don't see that number mentioned in the article. What tool are you referring to? - Nick at Pelican Parts  
quest1966 Comments: Can the driver's side upper guide rail pin be reused or does that need to be replaced? Thank you.
June 11, 2015
  Followup from the Pelican Staff: If it still fits tight, you can reuse it. However, for the cost you may as well replace it, for preventive maintenance. - Nick at Pelican Parts  
quest1966 Comments: According to the service manual, the head bolts can be reused if they have not stretched more than 3mm. Original bolt shafts measure 160mm. Upon removal, none of the bolt shafts are more tan 161mm. In your experience, is using new head bolts a better idea regardless of what the manual states? Thank you.
June 11, 2015
  Followup from the Pelican Staff: I ALWAYS replace them. take no chances on major repairs like this. - Nick at Pelican Parts  
quest1966 Comments: I am preparing to replace the head gasket on my 1995 E320, W124, M104.992 with HFM. Currently, what is the best sealant to use for the tips of the u-shape front cover gasket where it butts up against the cylinder head? Thank you!

Photo by gerryvz from 500eboard.com.
April 26, 2015
  Followup from the Pelican Staff: I would suggest a high quality RTV sealant. Give our parts specialists a call at 1-888-280-7799. They can get you some. - Nick at Pelican Parts  
distressed MB Comments: In figure 11 The article ask for a 17mm torx but torx only come in T-60 etc. is there a T equivalent? Where can I find this tool?
April 7, 2015
  Followup from the Pelican Staff: Fig 11 illustrates the fuel injectors being removed. DO you have the step number correct? - Nick at Pelican Parts  

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