BMW R25/0 - Rethread spark plug thread - Experience
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Autor Thema: BMW R25/0 - Rethread spark plug thread - Experience  (Gelesen 617 mal)

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krhoff

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BMW R25/0 - Rethread spark plug thread - Experience
« am: 08 Juni 2017, 18:31:05 »

Hi BMW friends,

The spark plug thread on my cylinder head is not in perfect shape. It is not very bad, but there is a small air leak, even when the spark plug is tightened.

I have a thread repair kit, similar to one on the attached picture. What is your opinion about such tools? Could this make a good permanent fix?

Thanks.
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BMW R25/0 - Rethread spark plug thread - Experience
« am: 08 Juni 2017, 18:31:05 »

cledrera

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #1 am: 08 Juni 2017, 19:32:10 »

Hi Krhoff,
my car, a BMW 523i, has two of this "Helicoils" an no problems.
Test the west, hope the best.

Only my 50 Cent.

Clemens
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rolf

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #2 am: 08 Juni 2017, 19:34:21 »

These Heli coils are Inserts ;D...some people said they are better than Helis
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #3 am: 08 Juni 2017, 19:52:21 »

Good to hear. I will "Test the west", but hope for no smoke. :)

Thanks a lot.
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bwprice100

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #4 am: 08 Juni 2017, 21:50:25 »

Hi krhoff

As others have said what you have is not a heli-coil, the look like a Timesert and are better where the thread is disassemble on regular basis.
I only use the spring like Heli-coil when the fastener does not come out often.

I hope this helps

Brian

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rolf

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #5 am: 08 Juni 2017, 21:57:18 »

You are right...timesert....not insert
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #6 am: 08 Juni 2017, 22:41:36 »

I also have the spring-like heli-coils, but probably not for M14. Yes, I agree on your point, Brian.

My set is not the "Time-Sert" brand. However, the quality seems okay. The tap is missing a part to follow the existing threads, as I have seen on other similar tools. This could make alignment a little bit difficult, but time will tell.

When I have done the re-threading I will make an update. Don't stay up all night - It could take several months before I decide to do the job. Thanks. :)

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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #7 am: 13 Juni 2017, 21:05:21 »

A small update. I looked at the spark plug threads more thoroughly, and it now seems to me that it has already been rethreaded by the former owner. See the photo below. What do you think? This does not look original to me.

It is possible to tighten the spark plug appropriately using the existing threads. My problem is mainly that I don't have an air tight seal.

Today I tested it with a new BP8HS spark plug, i.e. the projected insulator type, as recommended by Rolf in another thread. This I have tightened according to the standard advice. First hand-tight and then additional 1/2-2/3 turn. There is still a small air leak when I run the engine manually. Maybe I should just accept this?

Thanks.
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bwprice100

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #8 am: 13 Juni 2017, 21:14:28 »

The leak looks like it is through the insert.

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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #9 am: 13 Juni 2017, 21:30:25 »

Hi Brian,

Do you mean a leak between the outer part of the insert and the cylinder head? Well, I haven't considered that. That makes sense. Thanks. :)

If this is the case, I guess it would be difficult (at least for me) to make a good repair.
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #10 am: 13 Juni 2017, 23:11:38 »

To verify this, you could screw a wooden dowel or something into the Plughole, put some soapwater 50/50 around it and push the kicker down to see,
if it produces some bubbles and where they start.
If the Dowel woun't seal the plughole, you could cut off the thread of an old sparkplug and weld an appropriate diameter hexbolt into it.
Then apply some sealant to the thread and scew it in, then repeat the test. (maybe candle-wax can serve as a temporary sealant )
Afterwards the hexbolt allows you to remove the DIY-insert with a wrench and you can clean the threads thoroughly from the sealant.
Not the final solution, but at least you know exactly then, where it leaks.
Regards,
Sascha
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rolf

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #11 am: 14 Juni 2017, 00:13:49 »

best repair: welding the alloy (and now for a long thread spark plug)....no problems in future (I have done on all my heads)
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bwprice100

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #12 am: 14 Juni 2017, 06:18:40 »

Ues krhoff, that's what I mean.

Brian

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dequincey

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #13 am: 18 Juni 2017, 11:31:42 »

wow that looks awful.
how are the insterts put in place ? are they welded ? compressed by cooling and pressure ? screwed to the alloy ?

why dont you consider bringing the head to a machinist and get a proper repair ?
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #14 am: 18 Juni 2017, 23:03:45 »

Dequincey, I don't know how the insert is put in place. However, it seems solid, except for the small air leak. Does it really look that awful?

First, I will see if I can do a simple repair myself. I have thought about applying high-temperature epoxy metal to seal the outer edge of the insert. This is at least a quick thing to try.

If this do not work, yes, I may get it repaired by a machinist. I will probably wait for this until next winter. :)
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #15 am: 28 August 2017, 22:13:03 »

I have now removed the head and will soon take it to a shop where they can fix the spark plug thread.

Based on the attached photos, what is your opinion about the state of the valves? Thanks.  :)
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #16 am: 29 August 2017, 21:51:53 »

Hi krhoff

It is difficult to tell just from these pictures. A more important measure is how many kms have the valves done. I have not experienced it myself but the 7mm high km valves can drop their heads, so I beleive.

Brian

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #17 am: 29 August 2017, 23:14:05 »

The state of the valves?
They are on her places....the only thing you can say per photo ;D
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #18 am: 30 August 2017, 21:34:48 »

Unfortunately I don't know the valve kms. They were installed by the former (or former former) owner.  I think I will just keep the valves as they are for now. Thanks. :D.
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #19 am: 30 August 2017, 23:37:59 »

Hi.

I was in a similar situation some time ago....and a good friend recommended to at least replace the exhaust valve if I didn't know the history of it as that one is exposed to a lot more thermal stress compared to the intake valve...and thus much more prone to sudden death.... we're talking little money here and once the head has been removed anyway the effort to replace that valve (and maybe check the springs for any damages or being too much worn down) is no big deal.... especially when compared to all the effort and money required to rebuild the engine in case the valve fails....

Just my 2pence, Taz
« Letzte Änderung: 30 August 2017, 23:40:07 von Taz »
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krhoff

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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #20 am: 31 August 2017, 21:08:30 »

Thank you for your comment, Taz. I think I will order a new exhaust valve then. And new springs - they are cheap. :)

One more question: I noticed a small end play in one of the rocker arms. I believe that the rocker blocks are pressed on. Is is okay to carefully reduce the play using a vice or similar?
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #21 am: 31 August 2017, 21:23:12 »

Hi krhoff,
Yes, absolutely. You can also use a hammer. If to much play, hit the block - if to less, hit the rocker-axles.
This is the common way to "adjust" endplay on the rockers.
Regards,
Sascha
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #22 am: 31 August 2017, 21:35:12 »

Haha ... the fun way to make adjustments. :) Thanks, Sascha.
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #23 am: 31 August 2017, 22:16:09 »

Hello Sascha.

Hammer....ts...this high precision instrument is known as the Birmingham adjuster on the finer side of the channel   :schrauber:

Kind regards, Taz
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Re: BMW R25/0 - Rethread spark plug thread - Experience
« Antwort #24 am: 17 September 2017, 12:42:19 »

A got the head back from the shop. They gave it the "full treatment". They fixed the spark plug thread, replaced the exhaust valve, grinded the valve seats, planned the surface etc. Thanks for your helpful advice. :)
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