General Loud noise & vibration when raining heavily PLEASE HELP

[vexorg]

Creating steam which impeads the gas flow from the exhaust! meaning the car labours as the next charge of fuel/ gas struggles to vent from the cylinders. Once the steam /water vents from the exhaust, the flow returns to normal and so does the car!.
its just like if you bung the tailpipe with a rag sooner or later the engines gonna cut out!

Do you think the water is getting drawn though the engine? as in through the intake? because that's the only way the water would get into the exhaust

 

[portland_bill]

Do you think the water is getting drawn though the engine? as in through the intake? because that's the only way the water would get into the exhaust

The exhaust has a hole at the tail end. Water molecules are smaller than the hole.

Water drawn into the engine intake will do one of several things, dependent on quantity, relative to the airflow at the time.
A small amount may atomise, and turn to superheated steam during combustion, the expansion of which will give a power boost. Engineers have been experimenting with water injection for many years, not perfected yet. You may feel your car seems more powerful on a day with high humidity, and it will be, for this reason. The good mix of water in the air is great, but to do this in a controlled way requires a mixing airbox as big as your house.
A little more water, instead of atomising and creating steam, will instead cool the intake mixture, and the burn temperature, reducing power, but will still pass into the exhaust as water vapour. A little more still, may just put the fire out, causing misfires and unburnt fuel to pass into the exhaust. Bad news for a hot catalyst. The already hot exhaust will still turn in to vapour.
Add more water, and it will hydrolock, breaking pistons, bending conrods, and often destroying the block.
None of the above will cause a gurgle in the exhaust.

As the exhaust valve opens, the gases rush out of the cylinder. As the valve shuts, the gases are still moving, creating a depression behind them. This causes the gas to effectively do a two steps forward, one back, which is why at the tailpipe we can feel the pulsing. That pulsing will draw in water, but often fail to push it back out again. Don't know why, there is a physics explanation, not memorised. This is why when driving through floods, it is important to use a low gear and higher revs, to discourage the water flowing all the ay up the pipe. If an engine is left to tickover, with the tailpipe under water, it will draw water in, including up into the manifold, and into cylinders. Difficult to get one's head around, but it does happen. Great fun proving this at college, (1972/3), with an engine on a rig in the test workshop. Modern engines are more fragile, and probably not good for such an experiment. Vehicles that are set up for temporary wading will have snorkels on the intake, leaving the exhaust normal. Those used for longer periods in water will often have snorkels on the exhaust too.

So a big enough puddle can cause some to be drawn into the exhaust, where the heat at the tail end is lower, especially on a colder day, so it will sit as a puddle, and gurgle, taking its time to boil off.

 

[vexorg]

Water would be blown out the exhaust with no issues.

 

[steveras57]

Thanks for taking the time to do a detailed and lengthy explanation for what ive been saying Bill!!!.
I also am not a physicist ! but i know what im hearing and feeling, and think i articulated it in the best way possible, bearing in mind the o p,s discription of the symptoms he was getting!.
Grateful for your input and clarity!.

 

[portland_bill]

Water would be blown out the exhaust with no issues.

So a big enough puddle can cause some to be drawn into the exhaust, where the heat at the tail end is lower, especially on a colder day, so it will sit as a puddle, and gurgle, taking its time to boil off.

 

[vexorg]

There's still moving exhaust gases the will pull it out the tail pipe. Plus the amount drawn in must be tiny or it would sound like a burst exhaust under normal conditions.

 

[steveras57]

Got to say when i/we hear it inside the car it is very loud indeed! you would have to hear it yourself to fully understand!! .
As i said before there is a certain amount of resonance and reflected noise involved.

I have no doubt its a minimal amount of water! however if you go put a tiny amount of water in to your kettle and turn it on and let boil until the auto cut works your be closer to getting what the forces involved, and noise produced are like!

 

[vexorg]

Loads of cars have water in the exhaust starting from cold, you see them every day in winter, not once have I heard any noise form a car when cold. Some cars have water literally pouring out the tail pipe

 

[jrkitching]

Having read all of this thread, the only explanation which makes any kind of sense to me is that water from a tyre is being thrown up against an insecure or damaged panel.

If it were my car, I'd be inspecting the wheel arch liners very carefully.

 

[steveras57]

Yes of course! but at that point the exhaust system is cold so its just water(and cold so therefore denser and more easy for the pressure wave in the exhaust to force it out!) rather than super heated steam!.

 

[steveras57]

Will be checking with a fine tooth comb once I can get underneath for anything the slightest bit loose! to be honest I hope I find something and get proved wrong with my "boiling water" theory! as if thats the case its gonna be an easier solution overall!.

 

[jrkitching]

I can get underneath for anything the slightest bit loose!

as well as looking for anything loose, check that wheel arch liners aren't cracked or otherwise damaged, and that all the fasteners/clips that are supposed to be there are actually present and secure. A previous owner may have removed one for some reason and not replaced it securely. A large plastic trim piece vibrating against a metal panel can make quite a racket.

 

[steveras57]

Agreed !like i said fine tooth comb!

 

[vexorg]

Yes of course! but at that point the exhaust system is cold so its just water(and cold so therefore denser and more easy for the pressure wave in the exhaust to force it out!) rather than super heated steam!.

Your logic is wrong, but I'm going with the loose panel theory too.

 

[The Panda Nut]

Id be interested in a more detailed explanation from your mechanic as to why they think a damaged wheel would only cause "noise and vibration" under very specific conditions!!? ie driving through heavy rain and/or large puddles of standing water!
.
Surely if the wheel is that bad then surely it would be generating a problem ALL THE TIME!? and not just happening when a situation involving water is present!.

The theory just dont make sense to me! but i do accept that they have never experienced the problem so are basically working on supposition!

Totally agree. A damaged wheel will not change shape in the rain. Its clearly a tall tail at best. This will be one of these things.
Driveshaft with a ripped or leaking boot getting upset by water ingress
Wheel balance
Wheel bearing
Exhaust - just possible a mount is moving more when lubricated by water, though I doubt it
Some form of aerodynamic effect cauisng extreme drumming. If a panel thats glued in place is again under lubrication by water this is possible. Aero issues impossible to see when stationary but the most likely cause to be related to water Ive owned some 90 cars and driven coming on 1.8 million miles. Ive never had this from any mechanical cause. I have had it in the Focus, and that was bad design, also had something similar when the front screen became unbonded, I have experienced the symptoms from sheets on the roof rack. I would be looking at all the body seams for signs of movement, checking dirve shafts
The only other thing that just might be involved would be soem weird fault with the ABS casing a brake to operate. I think the chances of this are so remote though.
I did have a Citroen that had a freak hydraulic suspension fault that behaved as oddly but the 500 just isnt that complex.
If all else fails get someone to drive behind and observe from outside when this occurs I am sure something would be visible that would help throw some light on it.

One last thought. Has the car had new tyres fitted when or before this started?

 

[Nova1734]

Totally agree. A damaged wheel will not change shape in the rain. Its clearly a tall tail at best. This will be one of these things.
Driveshaft with a ripped or leaking boot getting upset by water ingress
Wheel balance
Wheel bearing
Exhaust - just possible a mount is moving more when lubricated by water, though I doubt it
Some form of aerodynamic effect cauisng extreme drumming. If a panel thats glued in place is again under lubrication by water this is possible. Aero issues impossible to see when stationary but the most likely cause to be related to water Ive owned some 90 cars and driven coming on 1.8 million miles. Ive never had this from any mechanical cause. I have had it in the Focus, and that was bad design, also had something similar when the front screen became unbonded, I have experienced the symptoms from sheets on the roof rack. I would be looking at all the body seams for signs of movement, checking dirve shafts
The only other thing that just might be involved would be soem weird fault with the ABS casing a brake to operate. I think the chances of this are so remote though.
I did have a Citroen that had a freak hydraulic suspension fault that behaved as oddly but the 500 just isnt that complex.
If all else fails get someone to drive behind and observe from outside when this occurs I am sure something would be visible that would help throw some light on it.

One last thought. Has the car had new tyres fitted when or before this started?

Yeah, new tyres were put on last September 2022 and the sound was there before and after.
The mechanic seems to be starting at the first point of issue, being that the noise originates from my rear left side when water splashes on the wheel. If that doesn't sort it, he'll investigate further but he's confirmed to me that there is nothing loose or out of place anywhere on the underside of the car whatsoever, including any of the panelling. I'd imagine he'd have checked the wheel arch liners in the process of investigating the underside of the car, he will be checking the exhaust as well.

It's a very hard thing to replicate, the conditions have to be just wet enough for the noise and vibrations to happen. A mate also suggested the ABS could be the cause but there are no lights on the dash when this happens, not even for a second.

 

[The Panda Nut]

Well if all thats is OK you need somone with MES connected while you drive to look at the abs system. If you can get a budding assistant to sit in and take a video when it occurs it would help. I would also say make sure your duck bill drains are clear of debris and that teh rubber bills are the right wat]y round that no water is getting into mthe clutch, thoough I don thi nk this is likley related. Also check you wiper motor and linkages are secure and teh bushes all good, f we could see the thing happening Im sure we could get it resolved. I am still su;picious of that roof pane. It could be 95% secure and difficult to get anymovement,but as I have found out the vibration from a panel moving just amillimeter is enough to make it feel and sound like the QEll is sliding off your roof.

I think my last thjough would be somethin g loose inside the back silencer that starts moving about when the temperature is changed suddenly or a freak wheel bearing issue with teh same cause. A bearing might be worth trying as they are not a huge cost to repalce but determining what side a noise is coming from is not easy and it would be an act of desperation. ALso check the brake backplate is sound fitting flush to the drum and without any sealing plugs missing if not already covered.
Asm you can tell I am fascinated by this. I had a hateful noise from one of my BX;s. It was pretty alarming. It was eventually diagnosed as a faulty air cleaner box lid. Too much plastic on a fin on the underside. It caused the lid to vibrate. An experienced technician went stright to it and fixed it for nothing in 5 minutes. I had been looking for months. Again a tiny fault but the noise sounded like terminal engine failure. No amont of poking prodding and leaning on things would have found that in a hurry. As your problem started at a point you can identify it figures, if no work was done something has fallen off or broken so look for places plastic underbody bits might once have been therea and make sure there are no missing rubber bungs and such like. Look for any signs of something missing. Look at the nuts holding wheel arch liners, not the screws on the edges. There are some plastic nuts on these things that are basicaally a push fit. Does that glass roof have drain tubes? Im also wondering if a blocked on could cause water build up and then air pressure acting on the water sets something off. All unlikely but also remotely possible.

 

[steveras57]

Im gonna call a halt here from my perspective until ive given everything the once over! HOWEVER finally saying that the noise is COMING FROM THE BACK LEFT SIDE UNDERNEATH! either the exhaust!!! or maybe but not convinced left rear wheel/arch etc etc!.

As my car is a colour therapy there is no chance its anything to do with the roof!!! and the tyres have been on it all the time i have owned it!

Your logic is wrong, but I'm going with the loose panel theory too.

one off us is right!

 

[Nova1734]

I might invest in an internal camera or something to capture it when it happens, if it happens again, after I get it from the garage.

 

[steveras57]

Where was you thinking of placing it then!