Can anyone assure me that I don't need to draw the pistons on my H reg. Proton 1.5 GLS, 80,000 miles? Cam belt snapped. Head off, slight dinges in pistons seemed o.k. replaced bent valves, new gaskets all round. Engine ran quieter and sweeter than for a long time. Then began to notice puff of smoke on starting and engine latterly occasionally idled rough. Then about 1500 miles after repair, started it one morning and it appeared to be running on one cylinder if that. Head off, all cylinders oily and very much more black soft coke than had accumulated during the previous 80,000 miles, no 4 ex. port very oily. Assumed valve guides causing problem and suspected valve seals but all seemed to be in order. Never thought to check the compression before dismantling. Did pop the head back on and with a plug in each cylinder in turn turned the engine by hand, could hear the compression leaking past the rings, should it?
I marked the position of the distributer before taking it off but do not think I did a further ig. timing check at the time, but whether that has any bearing I don't know.
Am waiting the arrival of a new head gasket when I shall do a proper compression check but in the meanwhile any advice, ideas even sympathy would be highly appreciated.
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Your slight dings in pistons may have caued a top ring to seize in it's groove.
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Thank you for the suggestion, that's given me something to think about. Meanwhile the oilway into the head is very adjacent to no. 4 cylinder which could well explain the extreme oiliness there but not elsewhere. Is it possible to have the ignition so retarded that the engine runs cool enough to induce severe coking up?
You can see the kind of straws I clutch at!
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IC, the more I think about it the more right I think you are when I eventually get the pistons out I will post the results here.
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Yes, three oil control rings fixed in their grooves, levered them out, cleaned heavy coke deposit off - rings free, fingers crossed.
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I think you'd find that the ignition being retarded would cause the engine to run hotter, not cooler.
Lifting a cylinder head typically lets oil run out of the oilway into the nearest cylinder bore and/or tappings. However this doesn't explain the oil burning that you report. You say you replaced some of the valves but not the valve stem seals. These seals should normally be replaced as they wear and harden but often still look good. Replacing valves through the old seals may easily have been enough to have caused them not to seal properly again.
By the way, it might be expected that the seals on the exhaust valves suffer most but it is the inlet valves which let oil by mostly, under the vacuum created as the piston descends on the intake stroke. The valve stem seals *may* be causing your problem, but no guarantees of course!
Remember to make sure the tappings in the block are clear of oil before refitting the head otherwise there can be a 'hydraulic' action when tightening the cyl head retaining screws and this can lead to incorrect tightening or, at worst, cracking of the block.
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In writing the above about valve stem seals, I missed your bit about the oil control rings being stuck. Perhaps this is the problem after all, though it seems strange that it has happened so suddenly.
I'm not familiar with the Proton -- is it their own engine?
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Thanks Dizzy, Mitsubishi engine ex. Lancer. 12v 1.5L, conventional, seems bombproof generally. Proton is H reg. I don't know whether they fitted a current engine or an earlier incarnation I expect HJ would know. Easy to work on. See the "Gudgeon Pin" string. I didn't realise my two strings would converge as they have. I did change the oil seals I can see that I put it rather clumsily and it looks as if I didn't, sorry.
I can only think that the rings were on the edge of seizure and the bang disrupted things, perhaps pushed them back into an unworn part of the groove. The long oil slot may weaken the wall sufficiently to have pinched them in? I don't know. If the groove is supposed to be 3mm they were all a very nice fit on a 3mm. feeler. Any how the rings were very tight in places, I wish I had noted just where. I had to lever them out with a needle & small screwdriver! Decoked they are quite free.
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Couple of thousand miles later, used no oil, no water, runs better than ever. Except idle trifle splashy (where trifle is very small) but cold slow running is a mess. Didn't alter the carb settings,honest. Ignition timing is spot on according to Haynes and timing lamp. I will start another thread asking for advice on this.
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