Monday 10 January 2011

Peugeot 205 Trio 1.1 - Head Gasket Change

One day, whilst driving home from work I noticed that the coolent level indicator on the dash suddenly flickered on then illuminated permentenly. I thought I haven't seen that before (in this car) but I'll just top the coolent up and bleed the system - or so I thought! It soon became apparent that after this symptom had repeated itself at ever regular intervals that the cylinder head gasket was dodgy.

 An additional symptom was excessive pressure in the coolent system, it was this that was pushing the water down in the radiator thereby triggering the low coolent level switch. The excess pressure would not go even if the car was stood for several days. If the cap of the expansion bottle was undone after a couple of days of none use pressure would be heard to release with bubbles comming from the radiator linking tube. 

To say that the cylinder head gasket had 'blown' was probably an overstatement. I suspected that gasses under compression in one of the cylinders were in fact being squeezed around/through the gasket into the water jacket like a one-way valve. Perhaps one or two very small bubbles at a time, but at 1000+ rpm they all add up.

The engine is of the TU1 type that had done 107000 miles without a gasket change to the best of my knowledge. I had suspected that the cylinder head gasket was not doing it's job for a while by virtue of a oil seepage from the front offside corner. Near this point a oil channel makes its way from the block to the head. This can be seen on quite a few old Puegeot TU type engines. After some diliberation as to whether the car was worth it and could I be bothered the only solution was to replace the cylinder head gasket. A factor in having a go myself was it had been a while since I had had the head off a car engine, the last being a 1978 Morris Marina (1.7) and a 1980 VW Polo (1.0); both with burnt out valves. So it was time to keep-my-end-in so to speak.


The following is a brief account of the job.

TU1 Engine Cylinder Head Removal



So as not to waste time on a potentially duff engine the coolent was drained followed by rocker cover removal then the head bolts cracked in the specified order. If one of the bolts had snapped in the block whilst undoing them then I probably would have pushed the car into the front garden until the neighbours started to complain that it was affecting thier house prices. A snapped bolt in the block can be removed somehow but it is a bigger job than I could be bothered with.

Old Gasket Postmortem ('Auto'psy)



The removed head gasket was in a poor condition as can be seen in the photograph. Parts of the it that were in contact with water has deteriated to such an extent that the metal ring part for the piston liner tops had seperated in some places. The visual evidence for where the gasket had eventually failed was quite subtle. The most likely point of failure can be seen in the photograph right at the bottom of the metal ring (6o'clock) it appears to have a fine possibly carbon track fron the piston side to the water jacket side. This photograph was taken after the old head gasket had dried out and the suspected failure point had become more apparent.

Preparing the Cylinder Head



Considerable time was spent on preparing the cylinder head and engine block surfaces in readyness for the new gasket. A bare stanley knife blade was used along it's entire cutting edge in a similar fashion to removing the exess paint off a window pain after painting the frame. I deemed the head to be finnished when as pictured the original machining marks were apparent. The head was not skimmed because it had not been subjected to a major overheat. It also was flat when a straight edge was offered up to it.

Reassembly



With both head and block surfaces prepared it was time to put it all back together. The cylinder head bolt holes were blown out using a foot pump to get rid of any debris that had fallen in them during old gasket removal. New bolts were used, these differed from originals in that they were star heads not hexagons. Reassembly was pretty much as the manual instructs. I planned to use a Laser tools angle indicator once initial first stage torquing had been done. It could not be used as intended however because it was of crap quality. The dial and its indicator needle both moved together as the head bolt was tightened!! Therefore in order to set the specified stage two angle I noted using the dial a suitable part in the engine bay (i.e bolt hole, bolt or bracket etc) and rotated the socket handle to another suitable engine bay part that coincided with the required angle. It was noticable that when tightenig force was released when the angle was achieved the star head of the bolt would spring back a few degrees. This was due to the torsion applied to the whole bolt.

New Cambelt



I didnot use a specialist tool to assertain correct cambelt tension because I did not have one. I considered a suitable tension to be that the belt could not be twisted more than 90 degrees with reasonable hand pressure. I knew this method to be subjective but comparison with other cars that have had belts changed at professional garages it did not seem an unreasonable risk to take. I considered buying a tool but a cheap one probably would not be consistant.

Summary

The car has now been used for a few thousand miles. So far the coolent level and pressure have been good. If I were to do the job again I would also change the valve stem oil seals as small quanties of blue smoke are emmited when the the engine is reved after it has been idling for a while say at traffic lights. I did not notice this before the head gasket change possibly because I was not looking for it. It has not got worse since the gasket change and it was not serious enough to fail it's MOT so I'll just keep topping the oil level up. The car starts well and has good performance.

Notes:

The Peugeot 205 is a supermini produced by the French car manufacturer Peugeotbetween 1983 and 1998. It was declared 'Car of the Decade' by CAR magazine in 1990. The 205 won 1984 What Car? car of the year.

This page was compiled wivout use ov gramma or spell cheka

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