Jump to content

Stripped sump bolt threads


Recommended Posts

Checking the front suspension bushes and I found the left hand inner rear wishbone mount was loose. That was my clunk when turning very tight walking pace left hand turns. Replace the nuts, torque them up and one problem fixed.

A few oil leaks around the sump so I thought I would check the sump bolts while I was there. The two front ones and one rear one have stripped the threads in the block.

I don't want to remove the sump and I expect there will some tricks to fitting heli coils with the confined access. Any suggestions if you have done this job? Would Loctite thread repair work?

Link to post
Share on other sites

Hi John,

I have not repaired a sump insitu but can't see any reason why not.

Drill the  striped hole (and sump) with the helicoil drill. Insert the coil through the sump flange and beyond and bingo.

The sump flange will have a little more clearance but shouldn't affect its working.

 

Roger

 

Link to post
Share on other sites

If it is the blind hole threads in the aluminium blocks front and rear that have stripped the use of a 2 part epoxy adhesive/filler like Devcon 19770 or K Poxy Aluminium or even JB Weld could be used to fill and then retap.  The arse of that repair is working upside down on oily metal.  Better solution would be helicoil as Roger has noted, but remember there is not a lot of hole depth to play with.

Could try re-tapping to M 8, existing is 5/16" (7.93 mm).  You would have to remember which screw went where if you stripped the engine in later years so as not to mix with the UNF items.

Cheers

Peter W

Edited by BlueTR3A-5EKT
Link to post
Share on other sites
10 minutes ago, RogerH said:

.......UNC threads...............

 

Roger

I am assuming this is a TR6 engine.

Yes I agree if it was not a 6 cyl TR engine.

They use 5/16 unf x 5/8" long hexagon headed screws (HU805 or SH605051) - UNC Equiv is HU855 or SH505051

Peter W

Edited by BlueTR3A-5EKT
Link to post
Share on other sites

Thank you all. I'll try retapping with M8 first as the simplest solution that won't preclude the other options later if it doesn't work.

Link to post
Share on other sites
On 12/24/2019 at 8:56 AM, RogerH said:

Hi Pete,

quite right. I misread the numbers. The screw is a SH605..  (UNF)   

NOT  SH505..  (UNC)   

 

 

Roger

That Zinc alloy block is a night mare, I had all the threads on my 6 in a poor state. I re-did them in UNC with Heli-Coils and deeper. On the set screws, I used very heavy washers made out of 3mm steel to cut down distortion on the timing cover. No leaks so far! But of course I was taught that soft metals require course threads. Then I found out that TR GB remake the blocs in Mild Steel, which is the way to go as they will take more torque on the threads. This is a major leak area on a 6.

Bruce.

Link to post
Share on other sites

On one front one I used an M8 tap first and it didn't work well, not enough metal left to grip the bolt.

I then used a generous amount of JB Weld on an M8 bolt which I screwed in, left for a few minutes and then gently unscrewed. I let it set until firm then put the M8 bolt back in but not tightened. Tomorrow I will see if it has set firm enough to give a reasonable torque.

The other front one and the rear one torqued up reasonably (no torque wrench, I did it by feel as I have for the last 45 years) with an M8 bolt screwed in without any preparation. 

Previously these three bolts had no torque on them so this should improve things but I don't expect this will be a permanent solution (unless it works well). 

Link to post
Share on other sites

After a couple of attempts I got the JB Weld to hold enough to get torque on the bolt. 

I have done a few 5km drives on a hot day, mainly city traffic but a few runs up to 4-4500 rpm, and it is dry. There was no torque at all on these bolts before so it should be improved. I'll see how it goes over the next few days.

Edited by John McCormack
Link to post
Share on other sites

Unfortunately with some use the bolts have lost their tension. It is still better than before I did anything but helicoils will be necessary on the front two bolts.

On the positive side, those front bolts are the main source of the engine oil leaks. Once done it will have fixed 90% of the oil loss.

Edited by John McCormack
Link to post
Share on other sites
35 minutes ago, RogerH said:

Hi John,

the original thread was 5/16 UNF.  I believe you opened it to 8mm. 

Can you now get a 5/16 UNC helicoil in there.?  That would be a good fix.

 

Roger

Hi Roger,

That is my aim. I can't see why it shouldn't work, the helicoil outside diameter is 8.334mm. I'll try to insert the helicoil without drilling the hole, do you think that would work

Edited by John McCormack
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.