Member Since: 28 Mar 2015
Location: Alps
Posts: 13
Damaged thread (hpfp) fuel pump belt tensioner
Replaced the hpfp following dutchvikings (https://www.disco3.co.uk/forum/topic187332.html) and French Collection (https://www.disco3.co.uk/forum/topic191857.html) guides. Many thanks to both of them.
Unfortunatly, after replacing the hpfp I damaged the thread of the fuel pump belt tensioner
Not sure, how best to fix the thread in this location! I'm thinking of either
- taking some 2K glue and a threaded rod (using a nut to fix the tensioner afterwards)
or
- try to manually drill, cut a thread and eventually put in a Helicoil
Anyway, I start by removing the valve-cover for better access.
Any comments and ideas are much appreciated.
31st Jul 2021 6:42 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10363
The thread is in the head.
Removing the valve cover is lots of work. If doing that you may as well take the head off to sort!
I would try and run a tap down the hole
31st Jul 2021 6:56 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4655
You'll still have the belt rear cover obstructing you and the cam pulley, but the cover can be split and the section behind the pump pulley removed. Though I'm not sure that will be of much help.
If you could get a tap in there it should come back easily enough (aluminium) provided it's straight and you didn't dog the tensioner bolt previously when tightening.
Do not attempt to remove the cam pulley under any circumstances!!yµ (idµ - eAµ) ψ=mψ
31st Jul 2021 6:59 pm
missesthi
Member Since: 28 Mar 2015
Location: Alps
Posts: 13
thanks for your inputs, Pete and Profsr G
just to get you both right:
you mean run an original M8 tap down the whole (and maybe using a slightly longer screw for some extra thread length to mount the tensioner afterwards)
or rather go for an M9 and drill the whole of the tensioner from d8 to d9?
31st Jul 2021 8:35 pm
motorworks
Member Since: 14 Nov 2019
Location: Usk
Posts: 401
Although the thread is into aluminium, it is unlikely that you have stripped it, considering the awkward access. The easiest solution is to carefully clean the thread with taps and leave it as M8.
Unless you take the head off, accurately drilling out and fitting a Helicoil will be very difficult. Fortunately, failure should only result in breakdown not major damage as with timing belt tensioner.Chris
31st Jul 2021 9:17 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10363
I assume you have just cross threaded it slightly
Therefore try the original size tap to clean the thread up.
Then try the bolt and see if it tightens.
You can’t drill in deeper. You may hit a coolant jacket. But I could have a look at a head to see if that’s where you get to
31st Jul 2021 9:40 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4655
As Pete K says, try that first and see how it goes before bringing out the big guns!yµ (idµ - eAµ) ψ=mψ
31st Jul 2021 10:14 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2459
If you have stripped the thread you can use a longer bolt, the threaded hole in the head is quite deep.
The original bolt only goes in a about 10mm, if you put something in the hole like a 5mm drill bit you can work out the depth so you can work out what length bolt to use.
I did something simular on a jag engine, it worked out ok in the end, held nice and tight.Andrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
31st Jul 2021 10:18 pm
motorworks
Member Since: 14 Nov 2019
Location: Usk
Posts: 401
I had look at the bolt hole on an engine out of car.
With bolt in the tensioner, there is 22mm of thread exposed plus 5mm unthreaded on the end. Depth of the hole is 29mm. In theory, you can get an extra 6mm of purchase with a slightly longer bolt.
I think your original 22mm of thread cleaned should be enough to secure the tensioner, trying to use the last few mm is not a good solution.Chris
1st Aug 2021 3:07 pm
missesthi
Member Since: 28 Mar 2015
Location: Alps
Posts: 13
thanks to all for the additional advice.
I reworked they way you suggested, but made use of a slightly longer, fully threaded bolt to use some extra thread length. the picture below showing the full hole length (up to the beginning of the blue tape) with the original screw.
- There is enough space for a tap without the handles
- added some loctite on the thread, since I was no longer willing to tighten to the 25Nm specified for this screw
- anyone having the issue when replacing just the belt and tensioner: having the hpfp and the crankcase breather out, gives a way better view and access.
Click image to enlarge
3rd Aug 2021 9:46 pm
Last Boy Scout
Member Since: 12 Apr 2019
Location: Ayrshire
Posts: 128
Good morning.
This happened to me last night after rebuilding from my Camshaft Pulley replacement so quite frustrating…. 🤷♂️🤦♂️
Regards the extra depth in this hole I have a couple of questions.
Is the extra bit threaded?
Does anyone know the thread size or is it just that standard 1.25?
Thanks.
10th Nov 2022 10:20 am
missesthi
Member Since: 28 Mar 2015
Location: Alps
Posts: 13
Hello
It is a M8 x 1.25 thread.
The extra depth is not threaded, that's why I used the tap to cut the thread.
Since the fix, the Disco has done more then 10k km, so far everything allright.
11th Nov 2022 9:01 pm
Last Boy Scout
Member Since: 12 Apr 2019
Location: Ayrshire
Posts: 128
Good afternoon.
That’s good to know. Thanks for the reply
Tapped out this morning and began the rebuild.
Longer bolt fitted with Loc Tight.
Fingers crossed that’s the end of my issues for a wee while. 😅
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