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Noisy B20F in a 1974 Volvo 145

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Old Sep 25th, 2021, 16:34   #1
marmiteman66
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Default Noisy B20F in a 1974 Volvo 145

Hello to you all. I have recently resurrected an old 145 that was sitting in a barn since 1992 and after a few road tests the engine has developed a strange noise. It is a knock, but doesn't seem to be related to ignition. It seems to go away as the revs go up. The valves are quite noisy too. I have been all over with a stethoscope. Alternator, water pump, engine block at each cylinder, oil pan, bellhousing etc. Can't seem to hear the source of it. Seems to be coming mostly from the manifold side so I am wondering if perhaps it might be something to do with the exhaust, or the mounting bracket, or the manifold itself. The engine mounts are old and soft, so maybe something is just clanging against something else. I am at a loss, but I know there are a lot of experienced people out there so I have mede a video and maybe someone somewhere has an idea. Honestly, at this stage, any ideas would be helpful, as I am all out.

Here it is, let me know what you think. https://vimeo.com/614528025

Warren
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Old Sep 25th, 2021, 18:48   #2
john.wigley
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Good evening, Warren. I'm afraid that for some reason I cannot access your video; also, although I did have several in period (my first Volvo was a 145E), it is a very long time since I had anything to do with a 1 - series car.

It did occur to me that your knocking might be the camshaft gear breaking down. That was not an uncommon fault in period (ask me how I know (!)) as it was a fibre gear bonded to a steel hub. If your car has recently been awoken after slumbering for the best part of 30 years, is it possible that the bond may be breaking down under load in protest?

A popular modification at the time in that event was to replace the fibre gear with a steel one, which, although slightly noisier mechanically, was much more reliable in service. I've no idea if they are still available, but I am sure that someone will be able to advise.

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Old Sep 25th, 2021, 20:40   #3
142 Guy
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Not exactly sure what noise you are referring to since noise is a normal part of a B20. I do on occasion hear what appears to be a knocking. That could be consistent with a broken tooth (or teeth) on the cam gear. If the hub fails completely on the cam gear that usually creates a lot of noise leading to no noise at all. The other cam related problem might be wear of the spacer on the cam gear which allows the cam gear and camshaft to move in and out creating a rhythmic tapping / knocking. Put you stethoscope right on the timing gear cover to try to determine if that is where the noise is originating from.

My only other advice would be is to set the valve lash in an attempt to reduce the normal B20 racket. This may allow you to discern the source of the particular noise you are concerned about. While you have the valve cover off setting the lash you can check the lift on each valve. Low lift on any of the valves would indicate a wear problem on the lifter / cam lobe for that valve - a problem that cams and lifters on the B20 are notorious for unless the 1974 already had the later lifter design. The noise could also be caused by excessive clearance on a particular valve.

If the engine was moving around a lot I would suggest looking at the support bracket for the exhaust system that attaches to the transmission. The bracket frequently fractures leading to a banging noise when the engine moves during acceleration / de acceleration. It typically does not generate a rhythmic tapping during idle unless the engine is rocking a lot at idle.
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Old Sep 26th, 2021, 19:15   #4
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Thanks for the replies. I have put the stethoscope directly onto the timing cover as this was an early suspicion, but, nope, sounds good in there. May have to remove the cover and make a proper visual inspection to be sure, but for now, I don't think this is the cause.

I will also, definitely, reset the valve lash and take a close look at each one's action.

I wonder if the bracket is the thing. The mounts are soft and cracked from all the time sitting, so the engine does wobble some. I have been working on tuning the kjet (another lovely story) and taken the engine to some pretty rough idles to try and find the sweet spot. Perhaps the combination of a super rough idle, on old and decayed mounts has caused enough movement to crack the bracket? If the crack is not large and obvious (which it is not), how could I test for it?

Last edited by marmiteman66; Sep 26th, 2021 at 20:31.
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Old Sep 27th, 2021, 04:05   #5
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Quote:
Originally Posted by marmiteman66 View Post
If the crack is not large and obvious (which it is not), how could I test for it?
On my 1971 142 E, the most effective way is to crawl under the car and inspect the bracket. If the bracket has cracked to the point that it is resulting in banging the crack should be visible; but grab the section of exhaust pipe just back from where it attaches to the down pipe and yank back and forth on it. If the bracket is cracked you should be able to see movement and hear the banging.
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Old Sep 27th, 2021, 12:11   #6
Derek UK
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Although it's masked under the general tappet and engine noise I'd say it's the cam gear starting to go. Listen to mine. It was already terminal then. I drove it happily down to my garage to have it changed (another YT video shows pictures) knocking like that. The previous day I had driven it back from the Southern BKV at Fort Nelson back to Kent! Cruised at 60 fairly quietly.
https://www.youtube.com/watch?v=iXxSRQ0johk
If you were using one of those mechanics stethoscopes you might find a wooden broomstick from the timing cover and pressed into your ear works better. Beware the fan!
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Old Sep 27th, 2021, 17:37   #7
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Hard to miss that noise. On a B18 / B20 you know its loud when it drowns out the noise of the valve train.

What is distinctive about the cam gear noise is that it repeats regularly and is a function of engine speed. The knocking that I heard in marmiteman66's clip was irregular - or I just missed a lot of the noise. That said, removal of the timing cover should provide a definitive diagnosis.
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Old Oct 6th, 2021, 23:56   #8
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Thanks again for the input. Been a busy week here, so little time to work on the car. I am putting her back in the garage this weekend in readiness for the winter, so will remove the timing cover and take a look.
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