AQAD40B injector retaining collars breaking

Have a weird problem with my injectors. Last week started up my STBD engine which idled normally for a couple of minutes then I heard this "poof" and continuing "poof poof" from the engine bay. On investigation I found that the retaining collar on No 4 injector had broken in half allowing the injector to lift from it's seating and combustion gases to escape around it. These collars are not that substantial so I thought that this collar had just failed due to old age. Anyway I had a new collar fitted to the injector and refitted the injector with new washers. I noticed that when removing some rags around the fuel lines I heard a sound like some small metalic object falling into the bildge. Couldn't find what this was so I started the engine. Immediately I had this "poof poof" again this time coming from No 1 injector. Once again the retaining collar was broken, and half of it was missing. I eventually found the other half in the bildge and conclude that this would have been the noise I heard when removing the rags. So it would seem that both No 1 and No 4 injector collars have more or less failed at the same time and one must assume that it is something common to both of them like excessive pressure in the combustion chamber or some other cause. I have checked the cooling water and although the water level is down a bit there does not seem to be any evidence of oil in it nor does there seem to be water in the oil. Has anyone experienced this sort of problem before or might have any suggestion as to the cause?

Don't know about the 40B, but re[;aced one on a KAD32 just recently. Apparently not uncommon to break. Expensive bits of junk aren't they!!!!! Have you check whether your aftercooler might be leaking? and white smoke?

Thanks Aliboy, Yes you are right about the expensive bit of junk. Have spoken to several diesel mechanics and none of them can suggest what might cause them to break except that they may have been overtightened and maybe overheated in the past. I thought maybe water in the fuel might be the cause but they seem to rule this out as water would be causing other problems as well. I hope it is just fatigue but for two to break at more or less the same time is unlikely. Don't know about the after cooler leaking, have'nt noticed any white smoke. How would you check for leakage and how would this effect the problem I have?

A leaking aftercooler can put water into the intake manifold and therefore into the cylinders leading to high compressions and hence more strain on the collars. Usually the first sign of this is white smoke. The aftercoolers are normally removed and pressure tested, usually when you get them acid washed every few years.

Your suggestion that it could be the aftercooler leaking and causing excessive compression makes complete sense to me even though I havent noticed any white smoke. Are these aftercoolers difficult to remove for joe bloggs or is it something a mechanic is required for. Trouble is we are just coming into our summer holiday season and getting a mechanic is just about impossible.

Sorry Colsum, have been away from the forum for a while. Just realised you are only 90 minutes from my home! Did you get this sorted?

Well sort of. Fitted a replacement collar to No 1 injector the other day and fired it up half expecting another injector collar to break or something else to happen however the engine ran normally with no evidence of white smoke or any other signs of problems. It's now had 2-3 hours runing and all appears normal. I'm not convinced this is over yet and time will tell. I still think your idea of an aftercooler leak is likely however I did show the two injectors to the bosh guys and they commented that if water is getting into the combustion chamber that this tends to polish the surfaces including the injectors and according to them the injectors were a normal colour. The whole situation is odd as none of the Volvo mechanics I have spoken to seem to have run into this problem before. Anyway I hope to get away on the boat next week for a few days so we will see what happens then.

If you need more parts, try calling this number 094263177. This is North Harbour Imports in Stillwater (coastal side of Albany). We sometimes get used Volvo parts from him, and this is where I picked up an injector collar for our KAd32's just a few months back. He does a lot of Volvo rebuilding, but unfortunately doesn't do outcall servicing. He is more knowledgable than most of the other Volvo service guys I have dealt with.

Thanks for the tip, I didn't know about them. In case you don't know there is another crowd, Four Seasons Marine 09 4283409 down at Gulf Harbour that stock a range of Volvo spares most of them sourced from Crom Marine Sweden which are quite well priced. I have bought filters, elbows, anodes, boots etc from them. They have a web site showing what they stock.