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Perkins Prima MDi Bosch VE Head Seal Injection Pump Diesel Leak O Ring Replacement

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  • Perkins Prima MDi Bosch VE Head Seal Injection Pump Diesel Leak O Ring Replacement

    My car had started to smell of diesel more than usual and I noticed that it was marking its spot more than usual too. After closely looking at the engine whilst running, I noticed that the injection pump was dripping diesel about once per second from the back of the pump, near the engine block, which was then hitting the pipework on it's way to the ground, coating everything with a diesel slick.

    I had found the problem but initially dreaded what the google search would suggest. Fortunately, it is not an injection pump out (and timing belt off) job to replace the head seal on the Bosch VE pump, as fitted to the MDi Perkins Prima fitted to Maestro and Montego diesels. Some more googling revealed that it is quite easy to destroy the pump internals by removing the pump head completely and that it required a methodical and relaxed response. Do not start unbolting bits of the pump without knowing exactly what you are doing.

    I completed the task today and apart from an aching back and some disintegrated tape, it was not too difficult to do. I couldn't find anything too specific about this on the Montego or Maestro, so thought I would do a quick guide, although the main document is on the website you can buy the new seal from. The head seal is thankfully universal fit across all VE pumps so that made things easier. The rubber degrades over time and it is also thought that modern diesel is not as kind on the rubber, nor is running on veg oil or biodiesel. The new seal I bought is made of Viton rubber and is said to be much more resistant to such things.

    Firstly you will need to purchase a new seal. I looked on eBay by googling Bosch VE Pump seal, and they are available from there. I also came across where you can purchase the kit direct. I strongly recommend reading the tutorial on the website as it gives a very good idea on the process.

    It is also a good idea to purchase some thread lock and some red rubber grease if you do not have some already. You will also need a small pick, some tape, a T30 Torx, Allen Key, spanners (8,10,12,14 and 17mm), degreaser, lubricating oil, some rags or blue roll and a container to catch any spilt diesel.
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    The first task is to thoroughly degrease and clean the immediate area around the head of the pump, which is the area the metal injector pipes connect. Clean the injector pipes too and the bracket holding the pump. This is to lower the risk of foreign bodies entering the diesel pipework when disconnected.

    Disconnect the throttle cable from the pump by sliding the metal cover back and lifting off. The bracket attached to the injection pump will also need to be removed. This uses a combination of the head bolts which are Torx, three Allen headed bolts and two 10mm which hold the pump and bracket to the block. replace the Torx bolts once the bracket is removed.

    Disconnect the fuel return from the injector pump along with the bleed off pipe to allow access to remove the stop solenoid. Use an 8mm and remove the wire before the solenoid itself. This is a large size so I used an adjustable spanner. Place some rag around the base as diesel will leak out and also remove the plunger, spring and rubber o-ring. Clean and place to one side.

    Remove the metal pipes running from the pump to the injectors. These are 17mm and you will also need a 14mm to stop the connectors unscrewing from the pump. If these do come out, be careful as there are sprung things loose inside, so don't undo these. I had a problem in I couldn't get one of the pipes off. This isn't a problem, so long as it is only one and you can get the pipe off at the injector end.

    With access much easier and a clear view of the pump head, I wrapped it with tape to ensure that the new o-ring would glide over the surface and to prevent it picking up and dirt or grit.

    WARNING - Before going any further, it is important to turn the engine until there is spring pressure on the pump head. To achieve this, I unscrewed the centre bolt clearly visible in the photo below in the centre of the injector pipe outlets. Choose a drill bit with a slightly smaller diameter than the thread and insert in the hole. Turn the engine over clockwise, slowly. I used a socket on the crank pulley, until the drill bit is most visible. Mark the drill bit if unsure. This will ensure that spring pressure hold everything in place when undoing the pump head. Remove drill bit and replace centre bolt.

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    With the pump now set correctly and good access to the head, it is now time to remove two of the bolts. I removed the one furthest away at the top and the closest at the bottom as the other two are longer as they also hold the throttle cable bracket on. Start to loosen the remaining two bolts, little at a time, switching from one to the other. You should find that the internal spring will push against the head and it will automatically start opening. Keep alternating until the o-ring is visible.

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    My kit came with an extra, longer bolt so I also threaded that in to ensure the head couldn't come out any further, although there was plenty of thread on the existing two...
    Using a pick and snips, I cut through the old o-ring and then cleaned up the locating groove ready for the new one.

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    The old o-ring was quite hard and when squashed had signs of cracking. It had perished. The new Viton ring appeared slightly thicker and much more elastic, which was useful for the next step.

    Using the red rubber grease to lubricate the tape on the head and the o-ring itself, I threaded the new o-ring over the stuck injector pipe down to the injector pump head (ideally you will be straight at the pump head!) Gently stretch the o-ring evenly until it is on the tape on the pump head. Then carefully allow the o-ring to go into the gap and seat itself into the groove on two sides. Use a torch and mirror to check that it is seated.

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    Then replace the two missing torx bolts. Using the pick to take the o-ring off the threads, remove the remaining two Torx bolts, ensure that the o-ring is completely seated before doing them up so that all four are back in and holding the head on. You can then take the tape off. I made the mistake of using brake cleaner, which turned the adhesive on the tape into a white sticky mess, as you can see it also adhered itself to the new o-ring, which I had to clean thoroughly before seating.

    Slowly do the four bolts up in small increments, ensuring that the o-ring is remaining seated. Once fully tightened it is then the matter of reassembling. After removing two of the Torx again for the throttle cable bracket, I dabbed each with thread lock to ensure that they wouldn't vibrate loose.

    Once everything is back together, keep pipe to injector unions loose and crank vehicle over until diesel is visible at each injector. Tighten unions and the engine should burst into life. Leak should be fixed for a good few years to come!

    I hope this helps. I was incredibly relieved when I saw that I could do it myself. It took me about three hours in total and was quite a nice job to complete (not a lot of grovelling on the floor). This is a guide only. Please do take care if attempting yourself and if unsure, consult a qualified mechanic. I will not be held responsible for broken injector pumps. Ensure that the pump is set properly before loosening the head bolts.
    Attached Files
    1985 Austin Montego 1.6HL Estate 'Uncle Monty'
    1994 Rover Montego Countryman 'Colin'
    1994 Rover Montego Countryman - L-Series Converted

  • #2
    Very good write up there
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