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Discussion Starter · #1 ·
Good evening,

I have been reading through these threads with great interest as I have a problem with the cam cover/rocker box on my 2006 Signum 1.9 CDTi. I don't believe it has been covered before, hence this new thread.

As seems to be an all too common occurrence with the Z19DTH engine, the water pump seized. This shredded the cam belt, one of the pulleys and of course as it is an interference engine, some of the rocker arms have snapped.

Well, at least I hope it's just the rockers, I would rather not have to replace the valves as well.

When I refitted a new cam belt, pulleys etc, got the all the bits back on the engine and started the car, air was being blown back through the air filter intake. But at least the engine started, no-one one was more surprised than me!

I have removed all of the bolts on the rocker box and it is still stuck solid onto the cylinder head.

The four Injector Retaining Bolts (or studs) seem to be the problem. Apparently corrosion can build up at the bottom of these bolts, where they screw into the cylinder head. The make removing the Cam Cover/Rocker Box very difficult.

In order to free the rocker box, I have been using a heat gun (normally employed as a paint stripper) and dribbling an oil/paraffin mix onto the bolts in the hopes that this will start to break down the corrosion. I have tried walloping the cover with a hammer and a bit of wood, both horizontal and vertical impacts (placing the wood on the exposed flange above the Cam Pulley) but there has not been much joy so far.

What irritates me is there isn't much in the way of vantage points in the engine design which will enable me to insert a pry bar and attempt to part the two halves of the unit with constant pressure.

I have attached photos to illustrate my bijou problemette

So, my questions are....

1) Has anyone here done this before?
If so, how did you do it? Any tips will be gratefully received.

2) Should I carry on with heating the bolts with an electric heat gun or switch to a blow torch?

3) Would a Diesel/Paraffin mix work better as a penetrating oil on the bolts? I think "Plusgas" uses a similar formula.

4) How tough are these Cam Covers? I don't want to use excessive force and destroy the one I have as they are rather expensive to replace.

5) As air was being blown back through the air filter box, would that indicate either broken rockers or bent valves, or both?

Thanks very much for your time!

Matt
 

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So I'm getting from this that you didn't replace the broken rocker fingers ?
Our experts have done plenty of jobs on this engine.
 
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Discussion Starter · #3 ·
So I'm getting from this that you didn't replace the broken rocker fingers ?
Our experts have done plenty of jobs on this engine.
Good morning,

Yes, your right.

I replaced the water pump, pulleys and Cam Belt, then reassembled the engine mount, etc.

On starting the engine, it fired up and ran. However there was air blowing back through the pipe that leads to the air filter box. This indicated either broken rockers or bent valves on one cylinder.

I do not have a compression tester to confirm this, unfortunately.

I am now at the stage where I am trying to get the Cam Call ver/Rocker Box off the Cylinder Head, but even after ensuring I have removed all of the bolts, it still won't budge, it is stuck fast.

It seems the main problem is corrosion around the bottom of the fuel injector studs where they screw into the cylinder head.

Matt
 

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The first thing I would suggest is investing in some proper Plus Gas and letting it soak in for some time.
I think you will have to try to unscrew the studs to break the corrosion.
You will probably need to use a proper stud extractor (if there is sufficient room) rather than trying to lock two nuts together on the studs.
Good luck!
 

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Discussion Starter · #7 ·
The first thing I would suggest is investing in some proper Plus Gas and letting it soak in for some time.
I think you will have to try to unscrew the studs to break the corrosion.
You will probably need to use a proper stud extractor (if there is sufficient room) rather than trying to lock two nuts together on the studs.
Good luck!
Hi Alan,

Thanks very much for your advice.

I am currently using an engine oil/paraffin mix and considering switching to a diesel/paraffin mix.

Apparently, PlusGas contains diesel as well as other things.

Thanks once again!

Matt
 

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Hi Alan,

Thanks very much for your advice.

I am currently using an engine oil/paraffin mix and considering switching to a diesel/paraffin mix.

Apparently, PlusGas contains diesel as well as other things.

Thanks once again!

Matt
As an alternative to PlusGas, you might want to try using genuine Coca Cola (the original recipe full sugar version).
I've never used it for this sort of problem, but have been successful freeing up old engines where the pistons have stuck due to standing for years, so it might work.
If you see what it does to an old copper coin, it will amaze you (just don't think about what it does to your stomach when you drink it)!
 

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Discussion Starter · #9 ·
Hi Alan,

I've heard that Coca Cola can work wonders with seized nuts, bolts, engines and whatnot. Goodness knows what it does to our bodies!

I'll get the Plus Gas and a stud extractor and go from there.

One type of stud extractor on the market looks very much like a drill chuck, I may have a chuck that could do the job, so long as I can avoid damaging the top thread on the stud.

In the mean time, I'll switch to a diesel & paraffin mix, dribbling that over the studs might do the trick. Perhaps white spirit might help in the mix as it evaporates, drawing the solution down the shaft via capillary action.

At least, that's the theory!

I'll avoid heating the stud with a blow torch as I don't want anything to catch fire. Especially my eyebrows.

Matt
 

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Discussion Starter · #11 ·
Hi Alan,

Thanks very much for the information, old chap. Unfortunately, that type of extractor will not fit in the space I have available by the studs.

I am considering buying either this...
https://www.ebay.co.uk/itm/IMPACT-S...559398&hash=item3d73463730:g:RpEAAOSwpaZblTHy

Or this....
https://www.ebay.co.uk/itm/Beta-Too...765488&hash=item467fd0b529:g:BqMAAOSwSzpbOyoW

I think the one resembling a drill chuck will be best, as the other is apparently for loosening studs that have not seized on.

Thanks again!

Matt
 

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Somewhere on YouTube I saw a successful stud removal with a solution of Aluminium Potassium Sulphate aka Alum (e.g. https://www.ebay.co.uk/sch/i.html?_...S0&_nkw=ALUMINIUM+POTASSIUM+SULPHATE&_sacat=0 )

I never used it in anger, but did some indoor tests on a rusty stud and nut. It certainly did free the nut although it took a few days!
In the video, the demonstration showed making a reservoir to hold the Alum solution with blue-tack around the stud to be freed.

Probably similar results to Coca-Cola, but the acids in CC might affect the aluminium of the head/block, whereas Alum (if my memory of chemistry serves) will (mostly) attack the iron.
[Like acids in C-C, alum is also used in foods - curries IIRC]
 

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Discussion Starter · #13 ·
Hi Mike,

Thanks for all of the information. I may use it as a last resort!

I believe Alum used to be available in blocks and sticks, used by wet shavers to stem blood flow when they lacerated themselves.

Styptick Pencil was a brand name and according to Google, it's still sold.

Matt
 

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Styptic Pencils are certainly used as you say, but there's no guarantee that it is Alum, not some other Anti-hemorrhagic.
Best buy something like in the link I provided above. It's bound to be cheaper than buying 10s of pencils to get the same quantity as a 1/4 Kilo bag of a known substance:)
 

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It's been a long time since I've had to change rocker arms on one of these. Not had any real problems getting the cover off. Also never personally seen valve damage from timing belt/water pump failure
 

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Discussion Starter · #16 ·
Good afternoon,
I thought I would give you all an update.

I managed to remove the rocker box cover, found that four rockers were completely wrecked and another four cracked. Therefore, I replaced all sixteen rocker arms, refitted the rocker box, fuel rail, cam belt etc. And of course I made sure everything was timed up correctly using a timing tool.

All seems to turn over correctly, however the engine wont start. Now, I know that these engines can be pigs to restart after major maintenance and overhaul, so I will keep trying.

One thing I will do tomorrow is recheck the timing, just in case the belt has slipped by one or two teeth.

Also, I will need to reprogram the injectors as, silly me, didn't realise everything was computer controlled these days. However, as indicated by other threads, having the injectors in the wrong order will not prevent the engine from starting, it will just run a little bit rough.

I will keep you all posted. Thanks for all of your help in the past!
 
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