Monday, 10 January 2011

Vauxhall Astra 1.4 LS (CN14NZ engine) - Cambelt Change and Associated Grief1.4 LS

MyVauxhall Astra 1.4 LS rattled especially after it was started. After a short period the rattle would go away. The car had done 110000 miles.

I looked up possible contributary faults in the Haynes Manual and on the Internet. Likely cause was the Hydraulic tappets playing up so the rocker cover was removed to expose said parts for examination.

The engine was rotated to Top Dead Center for all cylinders in tern to check if the clearences were way out which they were not. It was all put back together with nothing done. At this time I also checked the tension of the cambelt which seemed acceptable (i.e it could not be twisted more than 90 degrees without using reasonable hand force).

Obvoiusly after doing nothing to the car the rattle was still apparent. I bought a bottle of hyraulic tappet treatment liquid tipped it in but the rattle remained.

The car was reliable and it had acceptable performance but it just continued to rattle. I probably drove it for another thousand miles or so untill the was a step change with the rattle in that it was there all the time.

 Another symptom was also becoming evident in that with slight throttle control the rattle would briefly cease until the throttle was pressed again and vica-versa. Time to check the basics again. With the engine idling the trottle was blipped by hand using the connecting lever on the fuel injector. The source of the rattle was not clear but perhaps it was sort of near the top of the engine perhaps near the the cambelt end. Although I had checked the cambelt tension earlier I did it again but this time it was way out.

 It was at this point I determined the automatic tensioner had packed in. Maybe last time I checked the belt tension it was still just about working but intermitantly. Because the water pump is powered from the cambelt I decided to change that as well. It is recommened by professionals to do that anyway because generally speaking a cambelt failure is normally a result of something else failing.
The following is a brief account of the job which needless to say was not as straight forward as it could have been.

Cambelt Cover Removed

When the Cambelt cover was removed it could be seen that the belt was that slack it had been polishing up the left hand side of the cover a bitwhere it had been touching whilst flapping.

Also apparent on this picture is an indication of future grief to come. The water pump is just visible with bubbles eminating from around the sides. I watched a bubble grow and burst at this point and I thought it was strange as I had not needed to top the coolent up whilst using the car. However it was not a problem because I was going to change the water pump anyway

The Slack Belt

This is far too slack. The belt was also loose on the pulley. If it had been left much longer it would have come off and buggered the cylinder head valves up by virtue of the pistons kissing the valves.

Removing the Alternator Drive Pulley

To remove the cambelt the alternator drive pulley must be removed. The Haynes manual recommends geting an assistant ( in my case the old man) to put his foot on the break whilst undoing the bolt.

 The problem with this is that the bolt was that tight that the handle of the socket bar being used was obstucted by the engine support before all the drive train slack had been taken up. It also occured to me whilst doing this I'd better purchase a Hi-torque socket because they have considerably less chance of slipping off the bolt and rounding the corners.

Once a stiff bolt in a hard-to-get-to place starts to round off then the chances of you getting it undone deminish exponentially. Bad language is often a bye product.

I left the job until a suitable socket was obtained. In the intervening period I mentioned this problem to a pal who has considerably more practical engineering experiance than me. He suggested sticking the car in gear, jamming the sockect handle against bulkhead or engine support then pushing the car in the appropriate direction to undo the bolt. I tried it and it worked, did not even need an assistant.

Additional Cam Belt Cover Damage

When the pulley was removed it exposed the lower part of the Cam belt cover. For some reason it was loose hand had been worn away in parts by the the alternater drive pulley. The preceding picture also shows evidence of this.

The Removed Cam Belt Cover

The cam belt tensioner was removed prior to removing the largest cover. The tensioner bearing was still free runing with very little play. However the spring lever part of the assembly was seized solid. I was expecting it to have a rattling bearing to account for the noise experianced when the engine was running. something else must be causing the rattle I thought
This photo shows how slack the cam belt had become. There are a least three areas that have worn completly through.

Water Pump Removal

To remove the coolent pump three bolts required undoing except there were only two! The lowest one had corroded off. The other two snapped off when the spanner was applied -- BUGGER!

The whole thing was starting to look a mess
Considerable time was spent cleaning up the engine block so that a realistic apprasal could be made to the viability of sorting it out.

The Removed Coolent Pump

Corrosion was so advanced that the pump fell apart when removed. I read some where that the pump can be bashed out from behind if the water hose is removed. I considered doing this but since the large hose appeared in good shape I left it alone for fear of breaking some of the corroded block surrounding the coolent pump.

Drilling out the Old Bolts

Accessability is the main problem when working on a car. If what you needed to fix was on a bench infront of you car maintenance would be rather easier. Drilling out old bolts should be straight forward but not when the engine compartment side wall is in the way. 

Right angle drill attachements are made for this type of thing in mind. After measuring the available space and a trip to Machine Mart the Clarke model was purchased together with some high quality drill bits. 

The drill bits were shortened using a Black and Decker minidrill fitted with a cutting disk.
Two of the bolts were drilled right through but it was not possible with the remaining one so with carefull drill alignment (and a bit of luck) the remainder of the bolt was removed with about 75% of thread still serviceable.

Putting it all Back Together

The block was treated with rust converter then primed. A new coolent pump, tensioner and cam belt cover were fitted.
Note the new bolt that goes through the coolent pump housing.

Putting it all Back Together Some More

Care was taken not ot over tighten the bolt which had the damaged threads. Locktight was used in order to help it stay in position. It is my belief that this part of the Vauxhall Astra engine was designed by someone who had never worked on a car before overseen by supervisors and drawing checkers who were also pretty clueless.

 The water pump is part of the cam belt tensioning arrangement so has to be slackened off using small bolts that are difficult to access. Fortunately I was adjusting it with a engine drained of coolent. The C14NZ engine does not have a master drain plug, to fully drain it the pump and hoses need to come off - where is the bucket suposed to go. There is probably a technique to get around this dubious bit of engine design.

However once it is done it should not need doing for a considerable period of time. The remainder of reassembly was in line with the Haynes manual. Antifreeze/corrosion inhibiter was added to the coolent when refilled. I suspect because the car is not the most straight forward to drain meant that changing antifreeze was over looked when in private hands and hence the corrosion set in. I'll not think too much what other parts of the engine are like.


The car does not rattle any more and the engine is quiet. I think the rattle eminated from the cam followers due to the cam shaft not been driven properly. Perhaps it was the chaffing of the cam belt on it's covers but I would not have expected that t be a metal sounding rattle. Well it is sorted now.


Astra is a model name which has been used by Vauxhall, the British subsidiary of General Motors (GM), on their small family car ranges since 1979. Astras are technically essentially identical with similar vehicles offered by GM's German subsidiary Opel in most other European countries

This page was compiled wivout use ov gramma or spell cheka


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  2. Excellent info there PA. I'm just beginning my strip and replace of all those relevant components, including the thermostat. I made a crankshaft pulley locking thingy and posted pics of it at

    Regards, Pete.