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  #1  
Old 10-21-2020, 08:34 PM
clivealive44 clivealive44 is offline
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Default Oil leak on lower Idler/tensioner pulley

Hi, I got my cam and pump belts changed recently by a client of mine who is a Volvo mechanic, and has been for decades. He did it as a favour at his home for a very low price, said he had done them before, but a long time ago. I got him to change everything - pump belt, water pump, both idler pulleys, and cam belt.
When I got it back it was very smokey, I phoned him up, but he said he was too busy for the foreseeable future. So I managed to get the guy who did a good job on it last time to have a look at it. (he used to be a head mechanic at a Volvo franchise, and has all the tools, and had done done hundreds of them). He said the timing was well out, and it also had a bent valve. He fixed the timing and replaces all the valves.
When I got it back, it was running really well, but I noticed there was an oil leak at the front of the engine, which may have been there after the first mechanic's job. Took it back to the 2nd mechanic, he stripped it down, and found the thread for the bolt on the lower idler/tensioner pulley was damaged, and the oil was coming thru it. He tightened it as much as possible, and used some sort of thread lock/paste on the threat and the bolt head to try and seal it. The leak is now much reduced, it doesn't appear to be getting on the belt, but if you put your finger on the teeth of the cambelt pulley, or water pump pulley they are slightly damp. The 2nd mechanic said that the lower idler pulley is bolted into the oil pump, and in order to re-thread it you would have to take the oil pump out, which would involve taking the sump off. Which is a very big and expensive job.

Do people think that a slight amount of oil on the cam belt will greatly reduce it's serviceable lifetime? Any suggestions of an easier way to fix the leak?

Any advice, experiences, or suggestions welcome.
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  #2  
Old 10-22-2020, 09:06 AM
v8volvo v8volvo is offline
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Ouch, sorry to hear about your experience.

Unfortunately "Volvo mechanic" does not necessarily mean they are expert with the D24 family of engines, which are an Audi/VW product. Here in the US, supposedly well experienced specialist "Volvo mechanics" have been responsible for the routine destruction of D24 engines ever since they were first introduced, and then they spread bad rumors about the engines after there are problems, rather than acknowledging their own ignorance and blame.

It's an easy job for a guy with the right knowledge and equipment, as you know now, but proves to be impossible for someone who insists on convincing themselves that it's just like any other timing belt, where you just "line up the marks" and there's no reason any special tools or procedures should be needed -- the suggestion being that factory just came up with all those things for their own idle entertainment, and not for any good practical reason.

Anyway, sounds like this is not news to you, having learned the expensive lesson now.

The bolt you are referring to is probably the long skinny bolt that goes through the idler and the oil pump, and threads into the block. So, unfortunately, if the threads are damaged, then the damage is in the block itself. This is probably a result of over-tightening the fragile small thread bolts by a ham-handed mechanic, likely more damage from the first fellow you took it to sadly, as he was probably unaware that the torque spec on this delicate bolt is very low.

The proper repair would be to install a heli-coil or other kind of thread repair in the damaged hole in the block, but as you note that would be very difficult to do because of the need to remove the oil pump to get access, which involves tearing down the entire front of the engine (and pulling down the oil pan as well, which is labor intensive). There is also significant risk involved in the process of installing the helicoil because this particular bolt hole goes all the way into the crankcase, which is why you see oil leaking out now. That means metal debris from drilling and tapping the hole for the helicoil could make its way inside the engine and cause damage to the oil pump and other parts. You would need to exercise great caution to prevent this from happening.

Oil in any amount on the belt will shorten its life and threaten the engine. How much will it shorten the life of the belt? -- who knows. You'd have to use judgment since there is no way to predict.

I think now that you have gone to the work of repairing the damaged valve and getting new belts on all around, you probably ought to go the final mile and get the damaged block threads fixed properly. It might involve removing the engine -- chance to put in a new clutch too. Then you'll have a fully refreshed 940 TD. I think trying to live with the oil-soaked belt is probably a bad idea, both bad for the car and also bad for your stress level, never knowing how much or how little you should be worrying about it.
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83 764 D24T/M46 145k
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  #3  
Old 10-22-2020, 11:53 AM
clivealive44 clivealive44 is offline
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Many thanks V8volvo for your detailed response. Although there is another important external factor which affects my decision as to whether to go ahead with the repair. In the Uk, in all the major cities the different local councils have been introducing what is called Low Emission Zones, these vary from city to city, but what it means is that in English cities, most diesel cars manufactured before 2014, will be charged a heavy daily levy every time they use their car, or vehicle in the city, and in Scottish cities they will be banned outright, which means that I will soon not be able to use my car in Edinburgh, and old diesels will become next to being worthless. I think the decision regarding Edinburgh's LEZ has been delayed due to the Covid situation, so perhaps I will delay my decision until I find out what is happening in that regard. I can easily regularly get some indication of the condition of the belt by slipping the top cover off .
Thanks again,
Clive
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  #4  
Old 10-23-2020, 09:14 AM
v8volvo v8volvo is offline
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Good point, I understand many European and UK cities are now pursuing rules like what you describe. Probably justified in terms of public health, but the rules certainly will make it a hard argument to keep maintaining and operating a car like these.

Given that context, your plan of trying it out as it is for now and keeping a frequent eye on the belt does sound reasonable enough. It sounds like your second mechanic was able to take measures to keep the oil leak mostly at bay, so who knows, maybe you will get years out of it like this if it doesn't deteriorate any further. Oil contact in any amount is definitely not good for the belt, but a little oil mist is probably not as bad as being completely soaked. I think if you plan on popping the cover off every week or two and checking on it, you'll probably be safe enough for a while, assuming you are starting with a fresh belt. Watch for any sign of greasy or rubbery buildup on the teeth of the timing sprockets, or any signs of the belt swelling, softening, getting looser or tighter than it originally was, or changing in any other way to indicate it is being affected by the oil.

Of course also, if you ever start to notice evidence of any significant amount of liquid oil slinging out from behind the cover, or leaving drops on the ground, etc, in other words signs that the leak has suddenly increased, then you will need to take other action. For two reasons -- one, that it will mean the belt will have much more severe contamination and risk of breakage, and two, if the leak suddenly gets worse then that might mean the damaged threads for that bolt have let go. That would mean, in addition to allowing leakage, that the bolt is also no longer doing its job of retaining the timing belt idler pulley securely in the oil pump housing. If that idler pulley walks loose, then it will cause the timing belt to slip and valves and pistons to collide and you know what that means.

Good luck and let us know how it goes.
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86 745 D24T/ZF 340k lifted 2.5"
83 764 D24T/M46 145k
04 Audi Allroad 6MT 2.0 TDI
01 Audi Allroad 6MT 2.7TT
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  #5  
Old 10-23-2020, 09:35 AM
clivealive44 clivealive44 is offline
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Many thanks again v8volvo, for your excellent and detailed advice, will definitely bear all that you have said in mind, and keep you updated on any future developments
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  #6  
Old 10-23-2020, 02:07 PM
jpliddy jpliddy is offline
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hi sorry to here about your problem ive been lucky with the chap who does my cam belt etc. i do a lot myself but cant do cam belt .how many miles has your D24 done ?
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  #7  
Old 10-23-2020, 02:17 PM
clivealive44 clivealive44 is offline
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Hi jpliddy, it's done around 280k, it had done 110k when I bought it 14 years ago, I've been pretty lucky with it up till now. I'm the same, I do most things on it except the cambelt and pump belt, and the clutch, I would do the clutch if I had a proper ramp, but I have to do my repairs on the street.
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  #8  
Old 10-24-2020, 04:28 AM
jpliddy jpliddy is offline
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hi clive
had my D24 21 years now it had 50000 miles when i got it in 1999 now done 278000 miles im in stoke on trent staffordshire if your ever down this way ,
ive had a stainless exhaust .ditched the cat . blocked off EGR. replaced vacuum pump .radiator . plus plenty more jobs myself over the years . worked in your town plus around scotland when i was younger !
regards jim
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  #9  
Old 10-25-2020, 11:05 AM
jpliddy jpliddy is offline
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hi brickworks /huddersfield have all the service parts for cam belt change on our cars they carry VW LT parts so same engine ive said many times the cam belt set up changed 1993 onwards different belt /water pump and added a belt tensioner
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  #10  
Old 10-25-2020, 11:08 AM
jpliddy jpliddy is offline
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sorry company name is BRICKWERKS if you need them
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