Rear main oil seal (engine speed sensor) replacement on a mk5 VW TDI engine(also applies to Audi and gas engines)

difficulty: 3/5
back to 1000q: mk5 Jetta TDI FAQ and "how to" index"


Related links: 1000q: general TDI clutch FAQ

This article shows how to replace the rear main oil seal on a VW Jetta TDI 1.9L BRM engine.  The RMS holds the crankshaft speed sensor (engine speed sensor) sender ring.

I rated this difficulty 3/5 only because you have to remove the transmission and flywheel to get to the seal.  See 1000q: mk5 Jetta manual transmission removal and 1000q: flywheel/clutch removal on VW Jetta for details.  The rear main oil seal seals the transmission end of the crankshaft.   If the car doesn't have many miles and it's not leaking I would leave it alone.  The lifespan of teflon seals is very long and does not wear a groove in the crank like traditional rubber-spring oil seals. Therefore, it should last quite a long time without a problem. If the car has very high miles on it (300,000+) and if the flywheel is already off, I would consider replacing the seal. All mk5 and newer cars came from the factory with a teflon seal with no metal spring

Teflon seals must be installed without bending the lip.  The replacement seal includes a plastic guide sleeve installation tool.  It only fits one way and guides the RMS onto the crankshaft by stretching the seal a little bit for installation.  The new seals used on your car use tool T10134 shown below, to press the seal on. Do not lube teflon seals before installation! Let a new seal sit a few hours before filling with oil and at least 4 hours before starting the engine.

Any acid free hylomar gasket maker should be an acceptable substitute for the VW brand gasket maker.

The rear main seal is relatively expensive because part of the Hall effect engine speed sensor is on it.  The yellow tab on the seal is to hold it in place until installation. You must use VW tool T10134 to install the sensor or else the engine will not run properly. Details on the tool are below.

T10134 TOOL: It has several parts visible on the top view:
1. Tensioner spindle ( black threaded rod in center with Tension Nut on it)
2. Tension Nut (silver 24mm nut)
3. Assembly Bell (main body)
4. Guide Pin for gasoline engines (black ball handle - Not Used)
5. Guide Pin for Diesel engines (RED ball handle)
6. Seal mounting screws (the three black knurled knobs)

Parts visible on bottom (mounting face):

1. Tensioner spindle ( black threaded rod in center with Tension Nut on it)
2. Tension Nut (silver 24mm nut)
3. Assembly Bell (main body)
4. Guide Pin for gasoline engines (red ball handle)
5. Guide Pin for Diesel engines (BLACK ball handle)
6. Seal mounting screws (the three black knurled knobs)

Many thanks to dbandel for additional pictures and procedure. For support on this topic, please post in this VW Jetta TDI forum thread.

Rear main seal parts for 2005, 2006 VW Jetta TDI or similar

Torque Wrench
24mm deep well socket
flat edge or ruler
(3) M6x35mm bolts (ACE hardware)
(2) M7x35mm bolts (ACE hardware)
10mm socket, ratchet, extensions
2.5mm hex key
5mm long hex key
8mm hex key
10mm socket and 5mm allen head bit
green scotch brite (won't damage the metal)

1 rear main oil seal for mk5 BRM engine: VW# 038 103 171 s

VW tool # T10134 from VW snap on tools At the time of this writing (8/18/2011) the tool was about $237 (still cheaper than paying the dealership)

Procedure to replace the engine speed sensor or rear main seal on your VW Jetta TDI

Watch this video first but make sure to read the full DIY! There are important steps and notes not included in the video! I also made a small mistake pressing the installation sleeve in the wrong direction (visible in a few spots but fixed during editing). The sleeve doesn't latch onto the crankshaft so the seal wasn't damaged but if the sleeve sticks out beyond the seal lip, I suspect there is less chance of seal lip damage. The installation sleeve stretches out the seal so it can be pushed over the crankshaft. The seal ends up in the same position as it's being pushed forward but do it as instructed in the video and in this DIY.

This was performed on my demo engine out of the car. If the article needs any corrections showing this procedure in the car, please post in the forums and help improve the article! This demo engine was purchased to make quality writeups and not for personal use - please use the donate button above so that I can provide more great DIY!

Set the engine cylinder #1 to top dead center (TDC).  The camshaft rotates once for every 2 crankshaft rotations so if you are using the timing belt side to find TDC, use the crankshaft sprocket lock as shown in 1000q: BRM engine timing belt removal and check the camshaft to make sure it's at TDC and not 180 degrees off. The metalnerd crank lock is shown below. You DO NOT want to find out "after the fact" that you had the engine 180 degrees out!
vw tdi timing belt replacement

Remove the transmission.  See 1000q: VW Jetta TDI transmission removal for more details.  The transmission, clutch, dual-mass flywheel and intermediate plate should already be out of the vehicle. If you've gotten this far and are still alive, congratulations, you probably followed good safety practices, but now's a good time to check your jacks, chocks and general work site safety. Below is a thumbnail, click to enlarge.

Remove the pressure plate bolts (6x 9mm 12 point head bolts) and the flywheel bolts (6x 12mm triple square bolts).  See 1000q: flywheel/clutch removal on VW Jetta for details.  The flywheel bolt holes will only align in one orientation.  This ensures that the TDC stamp mark is correct.  If you are installing a new flywheel, make a mark on the engine to note where TDC is and examine them against each other off the car.  Double check the position of the TDC stamp on the new vs. old flywheel.
jetta tdi rear main seal

Pull the metal shim off.  It will stick on the tab at the top and some transmission alignment dowels.

The factory service manual's method to replace the RMS flange/rear main seal carrier is to remove the oil pan, install the rear main seal, and then install the oil pan with new oil pan sealant (gasket maker).  This ensures that the flange is sealed correctly at the corner and that the bead along the bottom of the flange forms a good gasket.  The alternative is to leave the oil pan on, then put a dab of gasket maker at the corners and an even smear along the oil pan-flange to seal it.  Since it's your car the installation method is up to you. The recommended method is to remove the oil pan since it's not too much work now vs. if it leaks later due to a poor seal.

Loosen the 6x 10mm bolts on the front face of the flange.  There are also 2x 5mm allen bolts on the underside.  To remove the oil pan, use a long ball head allen bit to loosen them due to the angle (shown below).  It's more secure than using extensions and a u-joint. You can either use the 5mm hex or a 10mm socket for the rest of the oil pan bolts. Remove them in an alternating pattern. Remove the Engine Speed Sensor using the 2.5mm ball head hex key. The screw holding the sensor to the old seal is hard to get to and at a slight angle, so the ball head hex key helps here.
jetta tdi oil pan

Gently pull the seal flange straight off.  Don't pry close to the sealing surfaces of the crankshaft or you might scratch it. Use m6 bolts, at least 30mm long as shown below to get it off. The service manual says 35mm but 30 is enough. Press off the old seal and sensor wheel together from the crankshaft using the three M6x35mm bolts. Thread the three bolts into the three holes provided in the seal. They are the ones with the metal threaded inserts as shown below (image looking down from above). Screw the bolts in using an alternating pattern of 1/2 turn each until the sensor wheel and seal flange come loose from the crankshaft:
vw jetta tdi rear main seal

If there's any corrosion around the flange or oil pan area, gently scrub it away with green scotch brite and wipe clean.  Green scotch brite is soft enough to not scratch the metal surfaces or put a scratch into the metal.  Toroughly clean all oil and old gasket maker off the sealing surfaces.  Don't use a paper gasket to seal the oil pan, only use a thin 2-3mm bead of gasket maker.  Any gasket maker should be inboard of any bolt holes to form an oil proof seal.

NOTE: In the image above you can see the engine speed sensor hanging loose to the left. Notice the angle of the hex screw relative to the plane of the seal which makes it a bit difficult to get out and back on.

Installation of new rear main seal on VW TDI

Take a look at your expensive, pretty new seal.
brm engine rear main seal

Notice the black plastic sealing lip support ring in the center. DO NOT remove this ring as it serves as an assembly sleeve to keep the teflon inner seal from becoming distorted during installation. Teflon seals are highly durable to wear but deform easily. Tool #T10134 is designed to accept this sleeve during installation.

Also notice the orange tab. DO NOT remove this until ready to do so later in these instructions. This tab keeps the position of the sensor ring relative to the seal and also to the engine speed sensor. If this moves even slightly THE ENGINE WILL NOT START or may start but run poorly and you will need to do this all over again (ask me how I know sometime).

Mounting the rear main oil seal to T10134:

1. If not already in this position, screw the tension nut down on the threaded tensioner as in the pictures of the tool at the top of the page. The tensioner has two flattened sides in the threaded section. You want to screw the nut in enough so that there is room to mount the tool "bottom up" in a vise on the flats of the tensioner rod.

2. Mount the tool in a vise:

3. Press the assembly bell down on the nut fully.

4. Lay a straight edge across the bell and tensioner surface as Shown. The tensioner surface (black) should be on the same level as the assembly bell. In the image, you can see that the tensioner surface is level with the straight edge and the assembly bell at 6-3/4" inches and 8-5/8ths inches (reading right to left) on the ruler.
T10134 rear main seal

In this image you can see that the tensioner is below the assembly bell. It should not be like this.
vw T10134

5. Remove the orange sensor wheel securing clip from the new seal.

6. Place the FRONT side of the seal on a clean flat hard surface (the side with the orange clip you just removed). Press on the sealing lip support ring (the black inner plastic ring) until it is flush with the hard surface. This ensures it is in the proper position when mounted in the tool.

7. On the rear of the seal, look next to the upper threaded hole where you put the top M6x35mm extractor bolt. There is a slight dimple mark (greyish circle in the image below) . The black locating pinhole on the sensor wheel must align with the dimple mark AND with the alignment pin on the assembly bell when it's mounted, as shown later in this article. The red pin is for gasoline engines.
tdi engine T10134

8. Mount the seal on the assembly tool with the assembly bell pin aligned with the sensor ring pinhole. Gently but firmly screw the three knurled seal mounting screws into the seal. Keep firm pressure on the seal during this step to ensure that the pin didn't inadvertently slip out of the pinhole. Make sure the seal is flat and level with the surface of the assembly bell before you move on and that the alignment pins didn't get out of position.

NOTE: I reversed this in the video so don't make my mistake. The installation sleeve won't fit over the crankshaft but I suspectit does help keep the seal away from the crankshaft until the tool is secured.
T10134 tool

Mounting Assembly Tool and Seal to Crankshaft:

1. Make sure the crankshaft flange and the sealing surface is COMPLETELY clean and free of grit, dirt, etc. It should look something like this (below) except you are going to do it correctly without the oil pan still attached, right?
mk5 vw rear main seal

2. Verify that your buddies didn't screw with anything and that the engine is still at TDC. Ask me why this is important sometime.

3. Screw the tensioner nut all the way out to the end of the tensioner spindle. Now press on the spindle shaft so that the tensioner surface moves out of the back of the tool as far as it will go. It should look like this - notice that the tensioner surface (black part with the two bolts) is now sticking out beyond the seal lip support ring. Make sure that the tool and seal are oriented with the flat part of the seal downward where it will contact with the top of the oil pan. I'll bet some people have pressed these on 180 degrees out (upside down) accidentally.
mk6 vw rear main seal

4. Secure the tool and seal to the crankshaft using the socket head hex bolts in the tool using the 8mm hex key. Do not tighten, you want it secure but able to move a bit.

From below looking up, it should look like this. Notice the flat on the seal aligns with the oil pan (which should be removed).
jetta tdi rear main seal replacement

5. Install the two M7x35mm "hardware store" bolts through the bottom two outboard holes in the seal body, and into the corresponding threaded holes in the block. These serve as guide pins while you press the seal on with the tool. This is important as it keeps the tool and seal from "cocking" and potentially damaging the seal:

***NOTE: the black pin is for diesel engines. The red pin is for gas engines.
tdi rear main seal tool

Here is another picture by A5INKY.  The black pin is for diesel engines, the red pin is for gas engines.
tdi crank seal replacement

6. Now that the tool is securely mounted via the tensioner surface, push the assembly bell by hand towards the crank until the sealing lip support ring contacts the crankshaft flange. Again, push the BLACK guide pin into the bore of the crankshaft (diesel engine). The red pin for gas engines. It may take a bit of wiggling. NOW tighten the 8mm hex head bolts firmly to the crankshaft. Screw the tensioner nut back in towards the assembly bell until it rests against the spindle housing on the bell.

7. Using the torque wrench and a 24mm deep well socket, tighten the tensioner nut to specified torque of 35Nm. Once this is done, there should still be a slight air gap between the engine block and the seal flange.

8. Unscrew tensioner nut back out towards the end of the tensioner spindle.

9. Screw the two M7x35mm guide bolts out of the block and remove.

10. Unscrew the three black knurled mounting bolts out of the seal.

11. Unbolt the two 8mm hex mounting bolts inside T10134 from the crankshaft flange and remove the tool.

12. Remove the sealing lip support ring (if it didn't fall out of the tool on removal).

You should have something looking like this at this point (except your oil pan isn't installed, right?)
tdi rear main crankshaft seal

Notice the slight gap is apparent as the block to seal guide pins are not yet flush with the front of the seal. The manual says at this point to check the gap between the sensor wheel and the crankshaft flange and ensure it is 0.5mm. If it isn't, reinstall the assembly tool and press the seal on again to specified torque. I "eyeballed" mine as I didn't have a caliper handy and it seemed fine.

If it's below 0.5mm, reinstall the tool and torque it 2.5 Nm higher. The service manual says 5 Nm higher but in my case it went from 0.4mm clearance to 0.6mm using 5Nm. Repeat until it's at 0.5mm clearance.

13. Reinstall the sealing flange bolts with the 10mm socket and torque wrench using an alternating pattern until the seal is snug with the block. Torque to 15Nm (11 ft-lbs). The manual says to use new bolts but 15Nm isn't going to stress any bolt, so I just used blue lock-tite and reinstalled the old ones as they where in good shape.

14. Reinstall the Engine Speed Sensor with the small hex key and torque to 5Nm.

15. Clean up the old oil pan sealing surfaces on the pan and block thoroughly and use a good quality silicone sealant (Permatex Great Stuff works well) and reinstall using 10mm socket and long handled 5mm ball head hex key. Torque to 15Nm (11 ft-lbs).

Reinstall the intermediate plate, flywheel, clutch and tranny per instructions in the related faqs listed at the beginning of this write-up.

I hope this helps some of you who have been contemplating replacing a leaking rear seal or damaged sensor ring using the T10134 special tool.

Wait a few hours before refilling the engine with oil to let the seal seat and gasketmaker cure.

Feel free to join the forums to get access to other great articles and to help others, thank you!