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tglatzel

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Discussion starter · #1 ·
Hi there, my Maserati GranTurismo makes some strange noise in idle (N) position when engine is at operating temperature. There is no strange noise when engine is cold. The noise disappears when pulling the oildipstick.
Any tips on how to solve this problem are welcome

This is how the engine sounds: l guess that's not normal:

https://www.youtube.com/watch?v=L1Ry30_KzEo
 
#2 ·
In have seen a lot of weird things in my 40 + years of dealing with cars, but this has to be among the most bizarre symptoms ever .. waiting for someone with solid mechanical experience to chime in and post a diagnosis, I'd be very interested in what causes that ..:|

Unless it's the dipstick top or stem rattling against the tube ( when the engine is cold it vibrates a bit more ) but there's no way it would make that kind of sound, IMO.
 
#3 ·
I'll give it a shot. All modern engines use a PCV system that generally requires the engine be sealed up with no air leaks, etc. When you pull out the oil dip stick, the engine is no longer "air tight" and anything that is related to the PCV / vacuum system will be affected, such as vacuum pumps...etc...maybe check those...
 
#4 · (Edited)
12 cylinders said:
I'll give it a shot. All modern engines use a PCV system that generally requires the engine be sealed up with no air leaks, etc. When you pull out the oil dip stick, the engine is no longer "air tight" and anything that is related to the PCV / vacuum system will be affected, such as vacuum pumps...etc...maybe check those...
Click to expand...
Sounds like a pretty solid theory to me ! :thumbsup:
And that can be tested when starting our cars cold , just pull out the dipsrick and see if the engine makes a comparable noise . I can try that tomorrow but if someone manages to beat me to it before then, please post . :smile2:
 
#5 ·
Occam's razor would seem to indicate the seal on the dipstick is not quite 100% and you're getting pressure leaking past making an odd squeak noise.

But hey!

C
 
#6 ·
Started the car today, pulled out the oil dipstick within the first 10 seconds of idle just to see if there was any sound - there was none - but since the OP indicated this was happening only at operating temperature after I drove the car for about 15 minutes to a grocery store ( should have been plenty of time for the engine to reach full warm up ), I pulled out the dipstick once again, but still no unusual sounds were present.
 
Discussion starter · #7 ·
Strange engine noise: update

Hi there: Corvette dude on the US forum replied: "It sounds to me like a crankcase ventilation issue.
I would look into the Oil disareator by the valve cover part #219111 and there 2 threaded plastic fittings by the valve covers
part #229987. They may be restricting the crankcase ventilation flow, and when you pull the dipstick it may be relieving the restriction. Let me know what you find, Those part #s may be different since your engine is the 4.2 and mine is the 4.7 ###

I have meanwhile replaced the oil disareator part number #219111. The noise is still there. I am now as well replacing the 2 fitting threaded union part number # 229987 and part number #231466 headconnecting vent pipe. I guess this means replacing the entire crankcase ventilation system. When checking in the garage we concluded, it must be the ventilation system. Another symptom is, that with engine on you can hardly remove the oil refill lid. IThe vacuumpressure in the crankcae sucks the oilrefill lid into the opening so that it is difficult to turn, when finally open you feel the sucking pressure in the opening. I will update when the fix has been done. Any othe rideas?
 
#8 ·
That is a pretty good one right there...You are on the right track...I can't remember if those fittings have an orifice in them or not ...You do have a good O-ring on #21911 ?...I want to say it has one...The fact you can't remove the oil filler cap is not normal..The crankcase is in a negative pressure, but it shouldn't be that hard...I assume you don't have any check engine light on? Jason
 
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Discussion starter · #10 ·
Hi guys, ... Aaron: to your question: I took the dipstick completely out, the noise disappears, but there is a strong sizzling noise of sucking air in. When I put my finger on, the noise returns similar to when dipstick is in and I feel the strong sucking / negative pressure on my finger.
The engine simply has to much negative pressure in idle operation. Should there not be a valve / air pressure regulator in order to ensure constant pressure? I have not found any valve which regulates air intake to balance pressure in crankcase Anyone has any idea?
 
Discussion starter · #11 ·
Jason, Indeed, no engine lights on.
It is exactly like you said: the engine should have negative pressure in idle operation and it indeed it has, but just too much of it. ,!!!

Reading about this type of problem with other manufacturers the general comment is, that the air supply in idle is wrong. The PCV system also has apparently and air in / and outflow and is linked to the general airinflow.. there should be a ventil or something which adjusts the pressure in the crankcase accordingly. I got no idea where this valve or airinflow regulator is with my engine. The parts I changed had no air regulating mechanism as far as I can see.

Maybe someone has some more suggestions.....
 
#12 ·
I don't want to mislead you here, and its very hard to diagnose these things without running a few tests. However, I'm not so sure this is related to a vacuum issue or pressure issue. I suspect pulling the dip stick and having the pressure drop is simply impacting something else, unrelated to the vacuum and pressure. Listening to the video, you can hear a distinct sound as the revolution progresses, pulsating as the cylinders fire. I bet if you put a load on the engine, the sound fades away and comes back as it returns to idle. Sorry, I can't help more than that without running tests.
 
Discussion starter · #13 ·
Maser077 said:
I don't want to mislead you here, and its very hard to diagnose these things without running a few tests. However, I'm not so sure this is related to a vacuum issue or pressure issue. I suspect pulling the dip stick and having the pressure drop is simply impacting something else, unrelated to the vacuum and pressure. Listening to the video, you can hear a distinct sound as the revolution progresses, pulsating as the cylinders fire. I bet if you put a load on the engine, the sound fades away and comes back as it returns to idle. Sorry, I can't help more than that without running tests.
Click to expand...
Indeed: putting a load on the engine the sound fades away and comes back when it returns to idle. It only occurs with engine on operating temperature. With cold engine everything is normal, no strange noise.
 
#14 ·
Has the intake manifold been removed recently? That almost sounds like a intake manifold gasket that maybe leaking..The air rushing by the gasket acts like a reed in a musical instrument...The fact it is not continuous makes me think it is related to one cylinder..You would generally have a rough idle etc., but it maybe ever so slight...Try spraying carb cleaner where the intake manifold meets the cylinder head and see if it disappears...Jason
 
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Discussion starter · #15 ·
Jason, We checked on leaking intake manifold spraying the manifold - cylinder head connection but could not detect anything. The sound is quite noisy and more similar to a squeaking belt not running fine, but we changed belts and wheels already and the noise is still there.

I hope not damaging the engine. The car itself runs fine. Rgds...
 
#16 ·
tglatzel said:
Jason, We checked on leaking intake manifold spraying the manifold - cylinder head connection but could not detect anything. The sound is quite noisy and more similar to a squeaking belt not running fine, but we changed belts and wheels already and the noise is still there.

I hope not damaging the engine. The car itself runs fine. Rgds...
Click to expand...
Hello tglatzel, I am the owner of a Maserati 4200 (model year 2002) and I face the same issue as you (same strange noise). I have found another topic on Maseratilife forum (specific to 4200 engine, but as GT engine is but derivative from 4200, it is not a mistake doing the link) the trouble is not fixed. So by reading your post, I am wondering if you, or someone else could help by providing the repair solution if exists...
Hope to read an answer soon.
Regards,
jg1974jg
 
Discussion starter · #17 ·
Hi: This is how the story continues:

In June the noise developed further: like a tractor with a Diesel engine. Short hard noise during cold start, and when engine got warm (normal operating temperature ) it sounded as in attached video:
Click to expand...
Unfortunately the solution was expensive: about 5000 Euro.
Apparently all these strange noises related to the fact that one or both cylinder banks have insufficient oil lubrication. The last noise in the video comes from a faulty camshaft regulator.
Around end 2010 this type of engine got a factory modification which solved the problem. In essence they installed a new return valve which ensures that some engine oil stays within the cylinder banks. Apparently the oil is running out of the banks when the car is not used for a longer period of time etc. I am not a technician and try to summarize what I was told.
To fix my car I got this engine update on my car. It sounds simple; a return valve, but apparently they have to demount a large part of the engine to install the fix. ...

The good news: all problems fixed, no strange noises anymore.
 
#18 ·
Hi tglatzel, first thanks a lot for taking from your time and giving an answer. At this stage my car is not concerned by the last video noise you've added. My car is concerned by the first strange noise you reported at the first bigining of this thread.
I have also identified an other Maserati owner (4200) that has the same "gurgling" noise, see this link: Maserati 4200 strange noise, but unfortunately, the thread is not ended, but there are some potential root causes mentionned in.
Your post is very interesting, because you mention that a return valve has been added to your engine; this seams to be in line with one of the different explanations available in the other thread I was refering to. One man says that the "breather tube" should be at the origine of this gurgling noise. I assume breather tube is what Maserati call "blow by system"; this system seams to be the piping system that manages engine oïl vapors. It is also reported that Maserati has designed new blow by systems (seams 2 new) in the 2002-2004 timeframe.

I have checked on specialized spare parts site, and I've found this drawing showing an old solution, but I did not identified yet the reason of this new design (noise??). If someone knows why this new design solution has been developped, let us know. Maserati design:
Image


I will continue my investigations, and if I find more precise explanation, or by chance fix my issue I will share for other Maserati owner.

Do not hesitate to comment, amend or correct this thread.
Cool that your noises have disappeared :)
Thread to be followed....
 
Discussion starter · #19 ·
Hi Jg,

Indeed I never found an answer for the "gurgling" noise which starts my thread. As I have written I replaced a lot of parts of the PCV system, but no solution. The PCV system is what you call blow by system.

After the gurgling noise a second noise developed; a short, hard rattle, only with cold start.
Three month later the last sound developed, only with warm engine, when changing load.

As with the factory repair of the new crankshafts and return valve all three noises have disappeared. Looks to me, that the crankshaft variator is the source of all these noises.

Crankshaft variator issues are unfortunately pretty common on all Maserati's with this engine, also your 4200 and relevant QP models. A lot is written on this. ...

Hope you find a solution. My car still is running perfect after this repair. All strange noises gone.
 
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