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Pelican Technical Article:

Setting the Engine at TDC

Steve Vernon

Time:

2 ? 4 hours

Tab:

$0

Talent:

**

Tools:

27mm socket, breaker bar, small Allen key

Applicable Models:

Mercedes-Benz W124 (1986-95)

Hot Tip:

Mark the direction of the belt if you remove it

Performance Gain:

Allows for other work to be preformed on engine

Complementary Modification:

Valve cover gasket

There are several jobs on your car that you need to set the engine at Top Dead Center or TDC. This article will show you how to set TDC by using both the crank and the cams as well as show you how to make sure your cams are properly timed to be at TDC. The M104 engine is a contact motor, which means if the timing between the cams and pistons (via the crank) are off you will do serious if not terminal damage to the motor. The motor needs to make two full rotations to complete a cycle. This means the zeroes on the dampener can line up 180 degrees off of TDC. The only way to check this is to pull the valve cover and check with the cams. Please see our article on valve cover replacement for additional assistance.

You will need to remove the fan, shroud and it really helps to remove the drive belt. Please see our articles on these procedures for additional assistance.

With the fan and shroud removed (we also removed the belt) place a 27mm socket on a large breaker bar and turn the crank clockwise (red arrow).
Figure 1

With the fan and shroud removed (we also removed the belt) place a 27mm socket on a large breaker bar and turn the crank clockwise (red arrow). Note: the radiator is removed in this picture but you do not need to remove it for this job. Just use care working around it.

Turn the crank clockwise until the marks on the balance dampener (red arrow) line up at the mark between the two zeroes with the witness notch (yellow arrow) on the motor.
Figure 2

Turn the crank clockwise until the marks on the balance dampener (red arrow) line up at the mark between the two zeroes with the witness notch (yellow arrow) on the motor. The motor needs to make two full rotations to complete a cycle, which means the zeroes can line up 180 degrees off TDC. The only way to check this is to pull the valve cover and check with the cams. Please see our article on valve cover replacement for additional assistance.

If you are not timing the motor and just want to do a quick check, you can look at the cam lobes (yellow arrow).
Figure 3

If you are not timing the motor and just want to do a quick check, you can look at the cam lobes (yellow arrow). If the motor is at TDC the lobes on both the intake and exhaust cams will be pointing up and slightly towards the center of the engine. If you are timing the engine or valve train and need more precision there is a small hole in the back of the cam sprocket. To time the cams at TDC install a small Allen key into the hole in the back of the sprocket and it will lie flat on the head by the cam journals (red arrow) when at TDC.

The same procedure applies to the intake cam.
Figure 4

The same procedure applies to the intake cam. If you are not timing the motor and just want to do a quick check you can look at the cam lobes (yellow arrow). If the motor is at TDC the lobes on both the intake and exhaust cams will be pointing up and slightly towards the center of the engine. If you are timing the engine or valve train and need more precision there is a small hole in the back of the cam sprocket. To time the cams at TDC install a small Allen key into the hole in the back of the sprocket and it will lie flat on the head by the cam journals (red arrow) when at TDC.


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Comments and Suggestions:
Willy Comments: Codes are p0341, p1340, p0325
December 1, 2016
Willy Comments: Codes are. P0341,p1340,p0325
November 30, 2016
Willy Comments: Hi after timing the engine crank shaft at tdc, cam shaft at tdc. Car start missing when driving at 60 to 65 mph check engine light came on. Code camshaft, knock sensor bank one and crack shaft sensor out of espec I don't know what to do. Timing is set up fine. Thanks
November 30, 2016
  Followup from the Pelican Staff: What are the fault code numbers? Possible timing is not correct. - Nick at Pelican Parts  
fanie Comments: Thanks. I don't have full instructions on the timing settings ,that is probably why I don't understand the proper way to set it .Could u probably give me step by step gidens .i am not macanicly inclined. I Got the engin stripped so I'm trying to assemble it correctly lol. Thanks for helping
November 19, 2016
  Followup from the Pelican Staff: I don’t have that info to share.


I would grab a repair manual. It will have the procedure, special tools and torque specs.


Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
fanie Comments: Will the timing be correct if I set the cams in there correct positions at 30 deg before TDC. Please help
November 13, 2016
  Followup from the Pelican Staff: The article does not recommend doing the procedure at 30° BTDC. Re-read the instructions. - Nick at Pelican Parts  
fanie Comments: It still confuse me that u set the timing 30 deg before TDC and then u say it must be at TDC

November 13, 2016
  Followup from the Pelican Staff: The article does not recommend doing the procedure at 30° BTDC. Re-read the instructions. - Nick at Pelican Parts  
JOJO Comments: MAY I KNOW WHERE THE LOBES INTAKE AND EXHAUST POINTING AT TDC .MY ENGINE SOHC 8 VALVE 190E HOPE YOU CAN SHARE SOME OF YOUR EXPERTISE IT IS VERY WELL APPRECIATED THANKS..HAVE A NICE DAY
September 6, 2016
  Followup from the Pelican Staff:
I don’t have that info.

We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
jojo Comments: thanks..
September 5, 2016
  Followup from the Pelican Staff: No problem. - Nick at Pelican Parts  
jojo Comments: hi, i have a 190e 1984 mercedes benz newly rebuild engine , it started smoothly,but iheard knocking from the engine.we check the lobes rocker arms the valves but they are ok.i change the timing tensioner.same knocking .it is possible the timing chain it self or the TDC..we are looking for the markings of the spocket of the camshaft but we cant find it.we just set the timing chain markings at the center of the sprocket when we install it..and by the way the engine is cranking but difficult to sart. i have to drop small amount of gasoline in the spacer of carburator to make it start..can you suggest how i troubleshoot it.?thanks..
August 31, 2016
  Followup from the Pelican Staff: I recall the engine not having timing marks. You have to use camshaft lobes and a small mark on the pulley to determine timing. I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Malik Comments: Hello, I had a broken timing chain om my 1991 300SL 24V 104.981. I have replaced two sets of bent valves, one set cyl1exhaust and one set on intake cyl6. I am ready to put it back together. I have set the crankshaft to TDC, then setting the head camshaft into the TDC position with the 4 mm Allen holding the cams, OK. Then at that time I can put the head on the block and bolt it down without any valve interference? Then with the crankshaft and the camshafts set at TDC I can start installing my new timing chains also the oil chain broke at the same time. Then would the timing be set to go? I know I still have to install the new chain rails, guides and a new chain tensioner. Then I reinstall all the front of the engine equipment.

Thanks for any help
June 27, 2016
  Followup from the Pelican Staff: Yes, as long as the crank and cam are in TDC, you can bolt them down, then install chain. You will not be able to make major timing adjustments once the head is on. - Nick at Pelican Parts  
Brian Comments: Hello, I had a broken timing chain om my 1991 300SL 24V 104.981. I have replaced two sets of bent valves, one set cyl1exhaust and one set on intake cyl6. I am ready to put it back together. I have set the crankshaft to TDC, then setting the head camshaft into the TDC position with the 4 mm Allen holding the cams, OK. Then at that time I can put the head on the block and bolt it down without any valve interference? Then with the crankshaft and the camshafts set at TDC I can start installing my new timing chains also the oil chain broke at the same time. Then would the timing be set to go? I know I still have to install the new chain rails, guides and a new chain tensioner. Then I reinstall all the front of the engine equipment.

Thanks for any help
June 23, 2016
  Followup from the Pelican Staff: As long as the crank is in TDC and the cams are also in TDC, you can assemble them safely without valve damage. One thing that can ease your worries, back the crankshaft off about 60° BTDC so all the pistons are slightly down. Then when the head is bolted on, bring the crank back to TDC, rotating the 60 you backed it off. Don't go any further or perform a full rotation though. - Nick at Pelican Parts  
Doug Comments: Turned out to be the vacuum modulator valve on the transmission bleeding into the intake through the vacuum line to #3 cylinder..no question.
June 10, 2016
  Followup from the Pelican Staff: Thanks for the confirmation. - Nick at Pelican Parts  
Doug Comments: So yes, you must mean that as long as the crank is set on TDC there is no difference between intake and exhaust TDC, as there would on engines with a distributor

..Anyway I completed my head gasket replacement and it was all timed perfectly and ran great with the excption that it still smokes white smoke when the engine begins to warm up! Starts and runs smoothly and sounds great, then begins missing as the idle drops when the start valve shuts down..and the idle control lowers the RPM..It runs clean for about five minutes then begins smoking increasingly until its billowing white-grey smoke, stinky but very wet..Any ideas what is up? I get a wet spark plug on the #3 cylinder! No leaks anymore fron the head, no water or oil and had both.

My suspicion is that now the head gasket is leaking at the engine block surface, on the back side..

The aluminum head was totally rebuilt with a fresh valve grind, new seals/guides...blue chip work. But the engine block had pitting on the surface around the cylinder sleeves and I was advised by the dealer it would seal okay, no worries..but then they admitted that JB weld was often used to repair old engines with corrosion pitting, fill and sand it smooth...No compounds are allowed. this is a 95 E320 gas engine with the M104 engine..And I find the techs comments that theyve never seen a bad bottom end on this engine..Its bulletproof. And indeed the bores look fresh with original crosshatch beautiful

Im feeling I still have a leak in the #3 allowing coolant/oil into the cylinder as the engine warms up..from the corrosion pits on the engine block..

Further question? any possibility of crack at the cylinder sleeve? has this been heard of? I find no reference to it anywhere but its the only other possibility..

Ive learned a ton and can easily redo the gasket installation once I get the right advice..do the JB weld filler and another new gasket..Its a one day job for me now!

Thanks for the forum!
June 3, 2016
  Followup from the Pelican Staff: A sleeve can crack, but usually it would be catastrophic. I wouldn't assume there is any hairline damage when performing a standard gasket replacement. - Nick at Pelican Parts  
Doug Comments: diddnt reay get the question, I was unclear, sorry..The marks will be at TDC every rotation..I was asking how do you know if its the compression TDC or Exhaust TDC ..but actually there IS No diffreence until you set the cam timing with the little holes. And yes..you must set the cams on the marks rotating with the engine 30 Deg BTDC..for non interference safety..This engine with no distributor is like a two stroke on the bottom end..ONly the valve timing creates the four stroke cycle BC there is no distributor drive train or gearing..I see comments like "make sure the whole engine is on TDC, not just the vibration damper" and Im going??? Whole engine? They must be referring to the valve train..which one sets on the TDC at the point of timing..Hope this clarifies for everyone..
June 2, 2016
  Followup from the Pelican Staff: It doesn't matter on the crank, on the cams, the tools only line up at compression. You can use the photos in the article, look at the camshaft lobe position. - Nick at Pelican Parts  
Doug Comments: so if we ahve removed and are reinstalling the cams, for a head rebuild...how do we know if we are "0" degrees off if the marks line up but we dont know if this is intake or exhaust TDC...
May 24, 2016
  Followup from the Pelican Staff: First get the crankshaft to TDC. Then check if the camshaft alignment tools fit intot he cams as shown in the article, before installing the head. If you have to rotate the engine to align with the head installed, due to timing being off. be sure all the pistons are down to middle of the travel before rotating. - Nick at Pelican Parts  
oliver Comments: good
September 25, 2014
  Followup from the Pelican Staff: Thanks - Nick at Pelican Parts  

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