Inlet manifold rattle but only when dry

chubbygordito · 18th May 2016, 15:52

I've narrowed down my rattle to the inlet manifold, the 5th chamber along.

I replaced both vis motors in the hope it would fix it....but still there.

However, when its raining/rained and the road is wet, the tapping disappears completely.

80% of the time when dry, its tapping/rattling, especially around 2800-3000rpm, I'm assuming when the balance vis operates, and there is no noticeable pickup.

However 20% of the time when dry, there is no rattling, and a definite boost when the balance vis operates, and as I said above, virtually never rattles when wet, so it seems to be an intermittant problem.

Is it possible its just something sticking in the manifold which a good clean out would solve, or best to replace the whole manifold?

TomRS · 18th May 2016, 17:24

Personally i'd just rip the insides out...

Inlet manifold flaps are a ridiculous design and offer very little in the grand scheme.. they give a slightly better low down torque and slightly increase fuel economy.
But mainly for emissions,
I've removed a set on a previous 190 that rattled and it made it feel tons better, there was a nice flat gradual torque curve and barely noticed any loss in MPG.
Power felt a little more responsive lower down, no negative affects that i can note.
But each to there own, i have even de-flapped my RS6 which uses a similar design except the flaps are vacuum operated and are sandwhiched between the inlet and head.
They increased power and i lost nothing doing a before and after run on the same dyno.

So with that as my evidence just remove them! i wouldnt dream of paying £700 for a new manifold and i certainly wouldnt be entertaining a used one as its only a matter of time before that fails too.
Unless its done like 20k

chubbygordito · 18th May 2016, 17:36

Well I've agreed to swap my ZTT which had the cambelt go with a vgc inlet manifold....better than sending it to the scrapyard.

Once I've got the new manifold fitted, I'll rip the insides out of this one.

Don't want to end up destroying the manifold and having no car to drive.

Salad-Dodger · 18th May 2016, 17:56

When I bought my 190 I bought it knowing it had a rattle. I did a bit of research prior to buying and thought I could live with it until I could locate another inlet manifold, if that was the fault.
When I removed the vis motors I found that the guts inside the manifold had been removed by a former owner so I had to look elsewhere for the cure to the rattle.
Personally, I don't think that if you have a manifold that is rattling, it will rattle all the time. A wet road will make no difference at all.
Most manifolds will rattle on tickover and will get a bit quieter as the revs rise but there's no real rule-of-thumb.
Remove the power vis and grip the end of the plastic rod with your finger and thumb. Try to roll it. If it moves a lot, you probably need another manifold.
I've taken a few of these manifolds appart and I can tell you that its not succesful in all cases. Sometimes they break up and are only fit for the bin.
If you get to the point of buying a second hand example, make sure you know how many miles its done and how old it is. The date of the make is on a sticker underneath.
My problem turned out to be a loss of oil pressure and one big-end stripped of its white metal. There was no "knock" just a rattley sound driving at around 2000 rpm. At first I had a go at new oil and a look at the cam followers, then a check on the oil pressure and some silver in the filter made it much clearer!
Good luck. I can tell you though that a second hand engine was a whole lot less money than a new manifold! Steve

chubbygordito · 18th May 2016, 19:22

I've had a listen using a engine stethoscope, and its definitely coming from the butterfly valve area in the inlet manifold. Tried each chamber at at time and its deafening on number 5.

I've just been doing some searching, and I've found several posts that say the same, rattle when dry, less or none when wet.

Seems inlet manifold is made from glass filled nylon, which with age is very susceptible to moisture can effect the clearances.

I've been out this evening and tried a modified balance vis I've knocked up...manually open/close the flap. When in its normal idle position, I can rev the engine and there's only a slight rattle....if I turn the flap, it makes a much louder rattle.

I'm assuming that somewhere in there, something is wrong on the inlet to cylinder 5.

Once I've got the new manifold fitted I'll open it up and take a look.

Salad-Dodger · 18th May 2016, 19:57

Yep. I have a couple of scopes, and like I said, the guts had already been taken out. Just change the manifold for a known working item. If you have a vent flapping it meens it has come off the oporating rod. If that's the case the rod will have a lot of slop on it.
Really, its made of plastic. When you get the lid off you will see what I'm saying. All the rain in England won't shut it up if its flapping.

chubbygordito · 28th May 2016, 16:52

So today I got round to fitting the new manifold.

The "rattle" has gone, but the loud tapping is still there.

Its coming from the front right of the car (sat in drivers seat), and can be very loud at times. Its much worse in 1st gear.

It starts around 2800rpm and increases with engine speed, but only under load. I can accelerate up to 60 and its tapping away, moment I lift off, its gone....touch the throttle, its back.

This afternoon I went out for a drive. Started off in the dry, loud tapping.....then it tipped down with rain for 20 minutes or so, and the tapping stopped.

After driving back on dry roads, it came back after 10 mins or so.

So, I'm now thinking the crank pulley. When it gets wet, it quietens it down, but when it dries out, starts tapping again. The crank pulley has the rubber dampener, the same type as an old Fiat I had which rattled.

I've got a spare one at work, so hopefully I'll have a go at changing it on Tuesday.

18th May 2016, 15:52	#1
chubbygordito Newbie MG ZT Join Date: Feb 2016 Location: Devizes Posts: 29 Thanks: 3 Thanked 1 Time in 1 Post	Inlet manifold rattle but only when dry I've narrowed down my rattle to the inlet manifold, the 5th chamber along. I replaced both vis motors in the hope it would fix it....but still there. However, when its raining/rained and the road is wet, the tapping disappears completely. 80% of the time when dry, its tapping/rattling, especially around 2800-3000rpm, I'm assuming when the balance vis operates, and there is no noticeable pickup. However 20% of the time when dry, there is no rattling, and a definite boost when the balance vis operates, and as I said above, virtually never rattles when wet, so it seems to be an intermittant problem. Is it possible its just something sticking in the manifold which a good clean out would solve, or best to replace the whole manifold?

18th May 2016, 17:24	#2
TomRS Posted a thing or two Mk1 ZT 190 - Mk2 ZS 180 - Mercedes E63 AMG S - Ford Ranger Hawk Join Date: Mar 2016 Location: Middlesbrough Posts: 1,456 Thanks: 123 Thanked 409 Times in 281 Posts	Personally i'd just rip the insides out... Inlet manifold flaps are a ridiculous design and offer very little in the grand scheme.. they give a slightly better low down torque and slightly increase fuel economy. But mainly for emissions, I've removed a set on a previous 190 that rattled and it made it feel tons better, there was a nice flat gradual torque curve and barely noticed any loss in MPG. Power felt a little more responsive lower down, no negative affects that i can note. But each to there own, i have even de-flapped my RS6 which uses a similar design except the flaps are vacuum operated and are sandwhiched between the inlet and head. They increased power and i lost nothing doing a before and after run on the same dyno. So with that as my evidence just remove them! i wouldnt dream of paying £700 for a new manifold and i certainly wouldnt be entertaining a used one as its only a matter of time before that fails too. Unless its done like 20k

18th May 2016, 17:36	#3
chubbygordito Newbie MG ZT Join Date: Feb 2016 Location: Devizes Posts: 29 Thanks: 3 Thanked 1 Time in 1 Post	Well I've agreed to swap my ZTT which had the cambelt go with a vgc inlet manifold....better than sending it to the scrapyard. Once I've got the new manifold fitted, I'll rip the insides out of this one. Don't want to end up destroying the manifold and having no car to drive.

18th May 2016, 17:56	#4
Salad-Dodger Gets stuck in MG ZT-T 190 Join Date: Feb 2015 Location: Chatham Posts: 592 Thanks: 34 Thanked 66 Times in 62 Posts	When I bought my 190 I bought it knowing it had a rattle. I did a bit of research prior to buying and thought I could live with it until I could locate another inlet manifold, if that was the fault. When I removed the vis motors I found that the guts inside the manifold had been removed by a former owner so I had to look elsewhere for the cure to the rattle. Personally, I don't think that if you have a manifold that is rattling, it will rattle all the time. A wet road will make no difference at all. Most manifolds will rattle on tickover and will get a bit quieter as the revs rise but there's no real rule-of-thumb. Remove the power vis and grip the end of the plastic rod with your finger and thumb. Try to roll it. If it moves a lot, you probably need another manifold. I've taken a few of these manifolds appart and I can tell you that its not succesful in all cases. Sometimes they break up and are only fit for the bin. If you get to the point of buying a second hand example, make sure you know how many miles its done and how old it is. The date of the make is on a sticker underneath. My problem turned out to be a loss of oil pressure and one big-end stripped of its white metal. There was no "knock" just a rattley sound driving at around 2000 rpm. At first I had a go at new oil and a look at the cam followers, then a check on the oil pressure and some silver in the filter made it much clearer! Good luck. I can tell you though that a second hand engine was a whole lot less money than a new manifold! Steve

18th May 2016, 19:22	#5
chubbygordito Newbie MG ZT Join Date: Feb 2016 Location: Devizes Posts: 29 Thanks: 3 Thanked 1 Time in 1 Post	I've had a listen using a engine stethoscope, and its definitely coming from the butterfly valve area in the inlet manifold. Tried each chamber at at time and its deafening on number 5. I've just been doing some searching, and I've found several posts that say the same, rattle when dry, less or none when wet. Seems inlet manifold is made from glass filled nylon, which with age is very susceptible to moisture can effect the clearances. I've been out this evening and tried a modified balance vis I've knocked up...manually open/close the flap. When in its normal idle position, I can rev the engine and there's only a slight rattle....if I turn the flap, it makes a much louder rattle. I'm assuming that somewhere in there, something is wrong on the inlet to cylinder 5. Once I've got the new manifold fitted I'll open it up and take a look.

18th May 2016, 19:57	#6
Salad-Dodger Gets stuck in MG ZT-T 190 Join Date: Feb 2015 Location: Chatham Posts: 592 Thanks: 34 Thanked 66 Times in 62 Posts	Yep. I have a couple of scopes, and like I said, the guts had already been taken out. Just change the manifold for a known working item. If you have a vent flapping it meens it has come off the oporating rod. If that's the case the rod will have a lot of slop on it. Really, its made of plastic. When you get the lid off you will see what I'm saying. All the rain in England won't shut it up if its flapping.

28th May 2016, 16:52	#7
chubbygordito Newbie MG ZT Join Date: Feb 2016 Location: Devizes Posts: 29 Thanks: 3 Thanked 1 Time in 1 Post	So today I got round to fitting the new manifold. The "rattle" has gone, but the loud tapping is still there. Its coming from the front right of the car (sat in drivers seat), and can be very loud at times. Its much worse in 1st gear. It starts around 2800rpm and increases with engine speed, but only under load. I can accelerate up to 60 and its tapping away, moment I lift off, its gone....touch the throttle, its back. This afternoon I went out for a drive. Started off in the dry, loud tapping.....then it tipped down with rain for 20 minutes or so, and the tapping stopped. After driving back on dry roads, it came back after 10 mins or so. So, I'm now thinking the crank pulley. When it gets wet, it quietens it down, but when it dries out, starts tapping again. The crank pulley has the rubber dampener, the same type as an old Fiat I had which rattled. I've got a spare one at work, so hopefully I'll have a go at changing it on Tuesday.