An additional engine sound

I hear all the normal pd tdi passat 2005 engine sounds, but this morning I noticed an additional sound on acceleration. It sounds like a Harley or motorboat sound. A bum bum bum bum sound. No metal or banging sounds. Just the described sound mostly on acceleration, barely perceptible at idle. I realize this question is more difficult without being in presence of the car. There are no dtc codes thrown or difficulties in starting or operating the car. 178 k miles. Thanks in advance for suggestions.

Maybe cam?

Thank you. Will post as I find more answers.

Sound is gone.

Still heard sound, but less so on way home last night. This morning on way to mechanic there were no unusual sounds. Car was checked over and all they could find was engine cover rattling and making noise. I do not think that was the sound I heard yesterday, but am glad all is well today. Drove, started, stopped car multiple times today and all seems fine. Will be listening. Thanks for input.

highmileage said:

This morning on way to mechanic there were no unusual sounds. Car was checked over and all they could find was engine cover rattling and making noise.

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Specifically, did the mechanic remove valve cover and look at cam wear? When it happened to me, initially could only hear the popping (bum bum bum bum) intermittently and started off doing it only on acceleration, but over time (days or couple of weeks at most) the sound got more noticeable and more frequent including at idle.

My regret was not having it checked sooner so I could've gotten my ducks in a row. Research options, purchase without needing the part yesterday, avoid towing fees when the cam did crap out on me, and then the rental car charges b/c I had to have a car and hadn't planned for the down time.

Get the cam inspected. It only takes a few minutes.

Thank you. Good advice. Makes sense. As far as I know, he just listened. He did not pull valve cover. I will have that done. As they say forewarned is forearmed.

Car makes sound intermittently. Mechanic had opportunity to hear it this morning. He states that an exhaust valve is sticking open creating pressure at the intake and makes the engine sound. A second mechanic also said there could be a turbo problem with maybe the actuator. Can anyone hazard a guess as to what I am looking at? The problem does seem to come and go and is there less than not. In other words the majority of the time there is no noticeable abnormality. Thanks in advance. Are cylinder head/valve problems common with the BHW?

Thank you. Will not be able to get to it until early in the week, but will post any new info I gather. I just want to say thanks again to all who have given me input, to help understand what is the problem. I am not a professional mechanic, but I try to understand as much as I can. In this situation, if the cam lobe(s) is worn it would have an impact on the function of the valve(s), yes? Thus the problem could be initiated by the cam, but impacting the valve and producing the engine sound that was heard as a sticking valve? I appreciate this forum and the knowledgeable people who make it what it is. Thank you all so much!

Thank you for the explanation.

Could there be more internal cylinder pressure on the exhaust valve when it is forced open by the lifter than there would be on the intake, also causing more wear.

Update as to car. Took car to two repair shops and neither thought the problem was the camshaft, as they both said if it were the problem it would be there all the time and it is not. It does seem to be there more when the engine reaches temperature. One mechanic felt it was a sticking exhaust valve and the other felt it was a burned intake valve. Since you guys work on these cars all the time I feel comfortable with your analysis of a camshaft. I wanted to look at cam directly, so I set out to remove the valve cover. After an hour plus of tinkering, I could lift cover, but could not clear it's removal. I think main impediment were tabs on inside of cam sprocket. Tried rotating engine a little with 18 mm wrench on cam bolt but there was a lot of resistance and I did not want to force anything. Is there a technic for rotating cover to remove it without removing other parts? Also, is there a way to determine problem is only due to cam and not the valves, without removing the head? Thank you all.

I personally have not seen or experienced burnt or sticking valve on a PD motor but not saying it cannot happen, but is unlikely. I have seen lots of bad cams though.

Do not turn the engine with the cam bolt. You can bump the starter until you get the tabs in a good place to clear.

Do check those tabs when you reassemble everything. I accidentally bent one out and it cut the top of the cam sensor and made it inoperative. You can bend it back very easily.

Thank you the information. Thankfully, I do remember observing those tabs before closing up with TB cover and being satisfied with their position. That is a great tip. Thanks.

highmileage said:

Update as to car. Took car to two repair shops and neither thought the problem was the camshaft, as they both said if it were the problem it would be there all the time and it is not.

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Not true. The bupping sound started off intermittent with mine, although it was there more or less the whole time right before finally crapping out.

You got the valve cover off? So what does cam look like? Seems a bit odd to me that 3 different professional (?) mechanics are speculating whether or not it is cam when it takes 5 minutes to pop valve cover off to take a look to confirm.

Get ahead of it. Several registered vendors here with good replacement cam options that will save you money, versus waiting for breakdown and then taking (towing?) back to shop that might then source inferior parts or pay more for OE from dealership parts dept.

Good luck.

Thanks for your input. No, I did not get valve cover off this time because the tabs were in the way. Next time I get to it hopefully, I will be able to get them out of the way. This morning I rechecked the tabs and "bumped" the starter to rotate cam for practice and believe now I will get it off next time. Will post my findings. I have sourced and priced cam kits and not using car much to avoid unnecessary upset. Thanks again.

Finally was able to take a look at the camshaft this am. There does not appear to be a lot of wear, but the main thing that caught my eye was the lobe closest to the tandem pump. At what I will call the peak of the lobe the chamfer is gone for maybe 1 to 1 and 1/2 inches as it goes over the "point" of the lobe. Running my finger feels rough and sharp on the edge and it is enough to catch a nail. The contact surface of the lobe does not have any flat spots, but I am thinking it is early in the process of the camshaft going bad. The lifters are the black type. Would the black or silver lifters have likely been factory installed on the car? Just wondering if this job may have been done before. My gut level tells me that I am dealing with a cam as opposed to a valve issue. Especially since the bup bup sound is only there intermittently. Am I on the right track? Thanks in advance for your input.

Did some more reading and I feel satisfied that my situation is accurately described by a camshaft issue that appears to be specific to the PD motor and maybe BHW. The rough edge to the lobe and the bup bup sound is described here in these forums by gurus as classic to the PD camshaft issue. I also read a guru statement that the BHW engine did not come with black lifters factory installed. These posts were from years ago, as well as recently, so I can only assume that the statements are applicable. Based on my examination of the lifters, cam, etc. the lifters are clearly black indicating this job or part of it has already been performed. It does not seem reasonable that with 178,000 miles I should be putting in a third camshaft, lifters, bearings, etc.. But..... Again I want to thank all of those who so freely share their expertise to help hobbyists like me do things mechanically that we would otherwise not be able to do.