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MG MGF Technical - Cam bolt Failure.... Disaster!

Hi all.

Last Friday my engine started what seemed to be a tappet noise. I needed the car so I drove it for more than 50 miles (80km). Initially I tought it was an hydraulic problem with the tappets that cured itself when hot. The noise was intermitent, but on my final way home it was noticeable louder and permanent.

It was 4 a.m., 16 miles to home and I was sleepy. 4 miles down the road at a red traffic light disaster struck. The engine was idling perfectly except for the rattle and then revs dropped to 500rpm. I cut off the ignition. I tried to switch it on and it started but not idling well. Tried to start the engine again. Dead. I know I shouldn't try but I always feel optimistic that it will cure itself...

Car was towed home and I start dismantling the engine yesterday. Further investigation revealed a loose camshaft bolt (right hand side) that caused the pin on the pulley to shear. Pulley is cracked and worn where the bolt washer touches it. I've taken the VVC mechanism apart and found that the face that touches the pulley is worn and the pin is sheared inside. Rest of the mechanism appears to be in perfect condition.

Car is a 06/1999 VVC, so after the recall 058. 59300 Km (30k miles). However, 6 months ago it changed the timing tensioner plus belts on a MG rover official dealer. May this be the cause? Do they commonly remove this pulley and didn't torque it properly?

All cams are in perfect order, plus tappets and belts. However, looking into the archive I unfortunately came to the conclusion that there's a BIG change that those 4 inlet valves are bent...

My idea is to replace the pulley, the bolt use the same VVC mechanism and do a compression test before removing the head. It this test shows a normal figure am I safe? You know, I don't want to remove the head and found out that everything is fine... Car was just idling when it went. Unless you say to me that you are 99% sure that valves are bent.

I'm doing the work myself, because I can't bear the idea of going to a lousy MG dealer. Let alone negociating with them, it's just to painful.

I've got pictures and will keep you updated. All comments will be greatly appreciated.

Valter.
Valter

Oh no Valter! :o(

Really sorry to hear that news.

Regarding the tensioner replacement theory, it shouldn't be necessary to remove the cam pulleys to replace the tensioner. In fact, the cam pulleys are usually locked in position with a specific tool - so the retaining bolts should not have been touched... perhaps the technicians didin't even closely inspect the area?

As to your plan of performing a compression test, yes, this is something that I was thinking of as I was reading your post. If a good compression, then it suggests that the valves are making a good seal with the seats in the head.

However, what makes me a little nervous is that as you say, the valves are almost certain to have impacted the piston crowns - albeit at low speed (relatively). Given that this will have happened, will the valve stems have been weakened? Are you just storing up problems for the future by not simply biting the bullet now and replacing all the valves etc and carefully inspecting the pistons themselvs?

Unfortunately, I don't have the experience to give you a balanced answer to that question. Perhaps it may be worth dropping a K-series expert like Dave Andrews a line to find out what he'd do in these circumstances?

Look forward with morbid fascination to seeing the pictures of your sick engine and subsequent rebuild. Fingers crossed that the damage is limited - and that all you need do is replace the damaged cam pulley and associated parts.

Might be worth investing in Mike Satur's cam-saver kit?
Rob Bell

:-(

'nuff said.

SF
Scarlet Fever

If the mech failed in the right place there would be no impacting (unlike a MPi where is is almost certain on at least one cylinder).
Even the slightest bend will show up in a compression test, so I would go this route.
Will Munns

:¬(

Neil

Forgot to add that the spark plugs on the 1 and 2 cylinders were whiter than those on the 3 and 4 cylinder. That means that those 2 cylinders ran leaner, proving the fact that the inlets were closed.

How did I found the problem out? Jacked up the car, engaged 5th and turned the wheels. I heard a noise and it turned out to be that pulley. Removing the camshaft cover and doing the same thing, I found out that the pulley was still able to rotate slightly the inlet camshaft. However when the cam hitted the tappet, it would turn backwards. So it wasn't able to compress the tappet. If this happened immeadiatly when the pin sheared, then those valves sttopped immeadiatly from working, meaning no impact.

At this point I just want to believe there's a chance...

Will, Thanks for answering a very important question: Any bent valve will show on the test!


Valter

Hi Valter,
sorry to read about what has happend - but there is a chance that you will get away without too much damage.
I guess that it was the front inlet pulley that had the sheared bolt/drivepin. If there was no real "cogging over" for the cambelt during the time the engine was running it could be possible that the inlet valves driven by the faulty pulley+drivepin simply went to the most relaxed position = closed ! Possibly with the help of a slight tapp from the pistons, but still not enough for heavy damage.
So the re-start was not possible because 2 cylinders had permanently closed inlet valves... But as suggested, a compression-test will reveal it all when you have fitted a new pin and new cambelt pulley.
No way I would re-assembly without either self-sourced 12.9-bolts or Mikes "Life-saver kit".
All the best and let us know how you get on,

Carl.
Carl Blom

Thanks for the replys!

I've been checking the workshop manual and there's seems to be no mention to the VVC mechanism itself. How to assemble it back together (I think I know, but I want to be sure).Where can I get that information?

Will, from memory I think you did a cam locking tool. Where can get this info?

I'm willing to keep the F alive, so I need all the support I can get.

Thanks!

Valter.
Valter

Valter - you'll need the K-series engine manual for information on that...
Rob Bell

Sorry about the troubles.

See email then. ;)

And have look to
http://www.mgfcar.de/VVC_mechanic/index.htm
(click all links) The docs are hosted with permission if the dutch SD1 Website webmaster.

> Do they commonly remove this pulley and didn't torque it properly?

May be, may be not. However the pin is said to be designed just only as locator not to take all the force. This should be provided from the right torque to the damn bolts.
Would recommend ass well theuprated bolts from Mike. I have bought a kit in last year. It comes complete (as usual) including a small bottle of Loctite.

Good luck with the repair. I Hope, Carl is right.

Best
Dieter

Dieter K.

Err, I'm afraid, forgot the image links posted already to another thread.
Not much help, but useful for education.
http://www.mgfcar.de/hgf/ch_000_0210.jpg
http://www.mgfcar.de/hgf/ch_vvc_100_1408.jpg
http://www.mgfcar.de/hgf/ch_000_0212.jpg
http://www.mgfcar.de/hgf/vvc2.jpg
Dieter K.

Yesterday, was a day of studying the VVC mechanism.

I'm trying to understand how it works and I think I've got it. Thanks Dieter!

What I do not have is instructions on how to assemble it properly. I've got a rough idea, but where can I get that? Mind you that I've separated the mechanism from the inlet cams. It was the only way to remove the sheared pin and reface the worn surface that mates the pulley.

Anybody have any idea why Rover specifically says: "It is essencial to ensure that front and rear inlet camshafts are retained in their respective VVC assemblies. If camshafts are removed from their VVC assemblies, then complete assembly must be replaced; It is not permissible to refit camshafts to VVC assemblies."

Sounds alarming, but in my mind I don't understand why I shouldn't. Hints, anybody?

Valter

Hi Valter,
maybee nothing more than an attempt to keep others (cam manufact.) away ;O). Obviosly there are those who can repair and re-assembly the VVC mechanism ,so anyway well worth a try.
Could of course also be that the VVC assemblies are match /machined as a set and by fitting a new part the whole assembly will be outside tolerances.
But this is not the case for you, this is a repair of a surface towards the cam-wheel that is not really taking part in the cam off-set process and the original part is re-inserted = no changes in tolerances. / Carl.
Carl Blom

The parts of each vvc unit are built to very fine tolerances. Unless you have these tolerances and the equipment and information to apply and check these then you are working in the dark.Providing the parts are refitted exactly as dismantled then you won't have a problem.There isn't any published information from either Rover or Airtex who manufacture these units, presumably to prevent 'tinkering'. If any parts were suspect then they would be changed as a complete new unit with camshaft (about £330)
If the bolt has worked loose then my advice would be to replace the VVC unit as the damage has been done and will work loose again. I would lift the head as well.
HTH.
Mike.
mike

Valter, did you get the email I sent you?
Rob Bell

Mike,

thanks a lot for the reply. You're always tremendously helpful.

Rob,

I've receive your e-mail and I thank you for that. However I already had that. As Mike says, there's no information regarding the VVC mechanism and how it's assembled.
Mike's life saver kit looks interesting and helpful.

I'm absorbing all the information I can get. Call me stubborn but I vowed to assemble it. The positive thing is that I'm learning a lot.

Valter.


Valter

I am keeping my fingers crossed Valter... the best thing I could do from here and being me without some usefull knowledge about the VVC mechanism.
Erik

Ok, I've got all the parts I need...so far. New Pulley, VVC seal, new washer, new upgraded bolt, new locating pin. Everything for £20. Dirt cheap.

VVC piece that was slightly damaged (worn exterior surface and little pieces of melted metal welded in) was refaced/machined. Perfect.

I've got instructions on how to assemble the VVC mechanism (Thanks Dave Andrews!), but I think I've got to remove the camshaft carrier.

I'll keep you posted.

Valter.
Valter

Great stuff Valter - I hope that you'll be writing up some rebuild instructions! :o)
Rob Bell

Rob, I'm learning (a lot) as I go!

Now, my main problem is lack of time...
Valter

This thread was discussed between 24/01/2005 and 31/01/2005

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