Common tasks on the early AJ V8 engines include replacement of the crack-prone plastic secondary/upper timing chain tensioners and leaking camshaft cover gaskets. The most difficult part of removing the left bank camshaft cover is getting the dipstick tube out of the way. It is not unusual to spend more time displacing or removing the dipstick tube than on the entire rest of the job. In this post I hope to offer tips to take some of the frustration out of this task, and to offer my reasons to not simply detach and displace the dipstick tube, but to remove it.




The dipstick tube is affixed to the cylinder head by a flange or tab secured to one camshaft cover stud with an 8 mm nut.




The lower end of the dipstick tube fits into the engine oil structural sump body to direct the dipstick down into the oil pan. Theoretically, once the 8 mm mounting nut is removed from the cam cover stud, the dipstick tube should simply pull upward and out of the sump body. But more often than not, the tube is so stuck that it defies all reasonable efforts to pull it out.

The other challenge is that once the tube is successfully pulled out of the sump body, reinstalling it can be frustratingly difficult because of the very limited access to its mounting hole.

The most common tip is to leave the dipstick installed in the tube to serve as a guide for reinstalling the tube, then gently move the tube side to side and rotate it on its longitudinal axis to try to loosen the bond between the tube and the sump body. Once the tube releases from the sump body, lift the tube only far enough to lay it toward the left wheel well to provide clearance for removing the cam cover, but do not lift the tube so far that the dipstick comes out of the sump body and your reinsertion guide is lost.

Another idea that has sometimes been employed is to use a tool such as a die grinder and small cut-off wheel to carefully cut a slot in the dipstick tube mounting flange, then bend the two ends of the flange away so the flange can be moved past the stud and the tube displaced just far enough to allow the cam cover to be removed. By this method, the tube doesn’t have to be pulled out of the sump body at all.

My position is that the dipstick tube really should be removed. All the way.

The reason is that the O-ring that seals the lower end of the tube at the engine sump body always hardens and leaks. It doesn’t usually leak rapidly, because of the tight fit of the tube, but it is also possible for the leak to be bad enough to contribute to lean engine running, as some of our members have found, and to adversely affect the negative pressure the crankcase ventilation system is designed to maintain. Replacing the O-ring will resolve these issues and eliminate one more oil leak from your Jaguar.




When a tube simply won’t yield, I start by applying penetrant along the length of the tube just below the mounting bracket so it follows the tube down to its lower end. Put a catch pan under the car and use plenty of penetrant to ensure the bottom end of the tube gets very wet with penetrating oil. If possible, allow it to soak overnight. The tube may yield by hand after it soaks. Try working one hand down between the engine and wheel well so you can grab the part of the tube that curves under the cylinder head to increase your grip.




Since we are planning to remove the tube, not just displace it, we can’t use the dipstick as a reinstallation guide. The handle of the dipstick won’t allow the tube to be removed without the end of the dipstick coming out of the sump body. So we need a substitute reinstallation/relocation guide. Some of the options include thin, flexible plastic tubing, heavy-duty string trimmer line, and heavy solid-conductor copper or aluminum insulated wire, which can be used as a “guide line” to direct the dipstick back into the sump body hole during reinstallation.

One of our gurus, Dale (crbass), mentioned using plastic tubing as his guide line, and one of the best options I’ve found is the thin polyethylene tubing used with my Mityvac fluid evacuation pump for suctioning engine oil and transmission fluid via dipstick tubes. This tubing is semi-rigid, with an outside diameter of 5.0 millimeters or 0.197 inch.





If you use heavy-duty string trimmer line, I recommend a type with a smooth (non-textured) surface and a diameter of 0.170 inch, which is a common size. Thinner lines can be too flexible.

Solid-core copper or aluminum insulated wire can be used. Copper is slightly stiffer. I recommend at least 10 gauge insulated wire, which typically has an outside diameter of approximately 0.165 inch.

Whatever you choose to use as a guide line, remember that the dipstick tube is S-shaped, so your guide line must be flexible enough to allow the tube to slide up and down with minimal resistance. Also, your guide line should be soft enough to pose no risk of damage to the inside of the oil pan, the oil pump pickup pipe, etc. For this reason, the use of steel wire may pose an unacceptable risk.

With the dipstick removed, insert the tubing, line or wire until it reaches the oil pan. Continue to feed your guide line in another foot or two, if possible, to give yourself a margin for error when withdrawing the dipstick tube.




Now the question is, how can additional upward force be applied to a dipstick tube that is well stuck? As our resident guru Bob Gauff (motorcarman) has described, a slide hammer works perfectly.

I know, it sounds scary. But this is the method by which modern direct-injection fuel injectors are removed, and it also works to remove dipstick tubes if proper care is taken. The key is to choose carefully the point where the upward force is applied to the dipstick tube. If you have a small slide hammer such as those used for fuel injectors or dent pulling and have a suitable hook attachment small enough to fit under the dipstick tube mounting flange close to the weld on the tube, you’re set.

If you only have a larger slide hammer as I am using here, loop a section of coat-hanger wire under the dipstick tube mounting flange and position the wire as close as possible to the weld on the tube. Positioning the wire or hook farther out on the flange would apply leverage where we don’t want it and could lead to the flange being broken off of the tube.





Twist the upper ends of the coat-hanger wire together to form a loop that your slide hammer hook can grab. I place a small piece of plywood over my fender pad to help protect the body from accidentally dropping the slide hammer (you don’t want to do that):






To pull the dipstick tube, lift up the slide hammer shaft to put upward tension on the coat-hanger wire. Then slide the weight up to perform multiple moderate impacts until the tube pulls out of the sump body. The goal is many repeated moderate impacts to move the tube a little at a time. Overly-forceful or violent impacts increase the risk of breaking the mounting tab off of the dipstick tube or damaging the tube itself. Patience and persistence are the keys. You can monitor your progress by observing the distance the tube mounting flange moves up along the stud.

Once the dipstick tube comes free from the sump body, carefully begin sliding the tube up your guide line:




You will probably find that there is not enough clearance to pull the tube all the way out of the engine bay. The upper end will contact the ABS modulator or fuse box framework.

Sometimes, it is possible to lay the tube sideways toward the firewall and achieve enough freedom to pull the tube up and out. If this works, don’t forget to keep your guide line pushed firmly into the crankcase as you slide the dipstick tube along the line.

If you can’t remove the dipstick tube by laying it toward the firewall, you may be able to pull it through the rectangular recess in the fuse box framework, as Dale describes in his tutorial. To displace or remove the fuse box, first disconnect the vehicle battery, then remove the power cable nut and detach the cable from the fuse box stud:




On the fender side of the fuse box is a locking tab. Pull it up with your fingers, or if it’s too stiff, apply a spritz of silicone lubricant or use soft-jaw pliers:




Now you can slide the entire fuse box toward the fender to disengage the locking tabs on its underside:




Now the fuse box simply lifts upward. You can detach the electrical connectors on its underside and set the fuse box out of your way.




If you find that the tube naturally wants to run into the ABS Module/Modulator assembly (ABS unit), you can move the ABS unit forward, toward the left headlamp. To do this, disconnect the vehicle battery to avoid triggering ABS / CAN codes. Now, lift up the large sliding latch on the ABS unit electrical connector, and while pulling the harness connector away from the module, push the sliding latch partially downward to clear the brake fluid pipes.




Then, detach the ABS fluid pump motor electrical connector:




Next, remove the two mounting screws along the left fender and the one screw at the forward end of the ABS unit. A 10 mm ¼” drive socket and long extension and a retrieval magnet make this easy:




Now remove the remaining mounting screw at the rearward end of the ABS unit:




The rearward mounting screw sits just under the edge of the ABS unit, and removing the other screws first allows you to lift the modulator assembly slightly for better clearance for your 10 mm ¼” drive socket as you turn the screw upward and out.

Now, you can gently push the ABS modulator assembly forward, toward the headlamp, while you lay the dipstick tube downward between the modulator and the fuse box framework. From this position, you can withdraw the tube. Remember the position of the dipstick tube as it comes out, because this will be the optimal position when you are reinstalling it.




Remember to consciously keep your guide line pressed firmly into the sump body as you slide the dipstick tube up and out of the vehicle.




Once you have removed the dipstick tube, position the guide line somewhere out of the way while you proceed with camshaft cover removal.




Here’s the reason we really want to remove the dipstick. The leaking dipstick tube O-ring. On this 1999 XK8 with AJ27 engine, the O-ring has a cross-section of 2.5 mm and an internal diameter of 9.0 mm. Up to VIN A30644, the Jaguar part number is KSH108624. From VIN A30645 the Jaguar part number is C2A1411. Clean the lower end of the tube thoroughly before installing the new O-ring.




After the cam cover is reinstalled, apply a thin coating of engine oil or silicone grease to the new O-ring and slide the dipstick tube onto the guide line.




Carefully work the tube downward until you can lay it in the same position it was in when you removed it.

I find it helpful to wiggle the tube as I slide it along the guide line toward the engine, to help overcome resistance. I will sneak one hand down between the engine and wheel well so I can gauge where the guide line leads. Don’t force things – let the guide line do the work of guiding the dipstick tube home. The job gets much more difficult if you kink the guide line.

If the worst happens and your guide line accidentally pulls out of the engine oil sump body, all is not lost. It helps to visualize the routing of the dipstick tube forward of the exhaust manifold, rearward of the power steering pump and through the opening above the power steering pump mounting bracket. The bracket on your engine may be somewhat different, but the location of the dipstick tube hole will be the same:





If you can fit one hand between the engine and wheel well, you may be able to feel the opening in the power steering pump mounting bracket. If you can feed the dipstick tube into that opening, it is not usually too difficult to move the end of the tube around in this limited area until you locate the hole into which the tube fits.

Once you have it started in its hole, you may find that it is nearly as difficult to reinsert as it was to pull out. I try to align the mounting flange with the cam cover stud and push the tube in at least far enough that I can reinstall the 8 mm nut on the stud. Then I can gradually snug the nut until it applies a little downward pressure on the tube flange.




Then I tap the top of the tube with a small soft-faced hammer. Again, moderate impact is all that is required. As the tube moves downward and into the sump body, I continue to snug the 8 mm nut to maintain a little downward pressure.




Keep tapping the tube and snugging the nut until the tube is fully seated, then torque the nut, reinstall the dipstick and you’re finished with this difficult part of the job.

Finally, don't forget to replace the O-ring on the dipstick. Shown below are dipsitcks from: 4.0L N/A (top); 4.0L S/C (middle) and 4.2L N/A. The dipsticks have different lengths or MIN and MAX hole positions, but they all use the same O-ring size. The size that seems to work best has a cross-section of 1.6 mm and an inside diameter of 5.1 mm. McMaster-Carr sells a package of 100 oil-resistnant Buna-N O-rings for $6.36 plus shipping, item 9262K136. Packages of 25 are available for similar prices but possibly lower shipping cost from sellers at ebay and Amazon. Jaguar does not give a part number for the 4.0L cars. For the 4.2L cars, the part number is C2A1411.




Cheers,

Don

 

I read on here years ago that slotting the tube mounting bracket helps with getting it off and on again, with regards to the cam cover gaskets.

 

Hi Sean,

As I mention in my post, slotting the mounting flange allows you to move the tube away from the head for cam cover removal, but it doesn't help if you want to remove the dipstick to replace its O-ring.

Cheers,

Don

 

Nice write up Don, the joy of knowledge bombs...I see this as How-To Sticky material.