Newbie here, 91 300te 4matic, 250,000.
SO went through a wash here in New Mexico (only a foot of water) and washed water over hood. Car died, started 20 min later. Drove 6 miles. Air filter wet, radiator sensor apparently shorted out, no water in oil (drained after sitting overnight). Now have a definite tapping noise you can hear standing outside of car. Used tubing to ear all over but do not get any sign of increased noise corresponding to the tapping (valve cover, injectors, exhaust manifold, block, crankcase, tranny, peripherals). Have not pulled entire airfilter assembly for access to that side. Any thoughts?

Great informative site. Have learned a lot through searches. Yes, I know, 91 300te 4matic, run, don't walk away.
Appreciated,
Tom

This is unscientific but I would put it in a warm dry garage, open the hood, point a huge fan at the engine for about 3 days.

if you got the intake under water you may have sucked water into the engine and bent a rod.

i hope not.

i would have an experienced mechanic listen to the noise.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

As explained to me, the water was a washover, not a submersion. The air filter wetness shows some indeed in the intake area.

If a rod, should I be able to isolate the location through stethescope, tubing technique?
What's bugging me is that I can't find the location of the noise and obviously don't want to drive it until I know what it is.
Maybe time to get the 86 xj6 radiator.
Thanks for your help.
Tom

I have heard a shorted plug wire make a definite tapping sound before. Think of the sound of jumping spark. Perhaps wet wires have uncovered a bad set of wires. Just food for thought.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

i am not sure how to determine it.

i bent a rod in one of my 6.2 gm diesels when a glow plug end broke off. the symptom was a very loud diesel like sound.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

the sound is not a real loud knock (yet!).
Drove the car about 3 miles - smooth. Have revved the engine in park to 5000- smooth. Idles smooth. Tapping frequency increases and decreases with engine rpm. Loudness level never changes. Oil pressure good.
Will check wires - good thought.

Plan to pull air filter assembly for better access to intake manifold side.
Thanks,Tom

The first thing I thought of when I read this post was a bent connecting rod. Do a compression test. If you've got a bent rod, the affected cylinder will have noticably lower compression. How much lower depends on how badly the rod is bent. If you do have a bent rod (I hope you don't), the noise you hear is most likely the rod hitting the bottom of the cylinder. Good luck

it could be bent only slightly. if so then a compression test may not reveal a big difference. any amount of rod being bent should show something on a comp test though. though the normal variation of the cylinders could mask it.

on a diesel 1.5 teaspoons of water will fill the combustion chamber. so with a gasser of similar displacement a bit over twice that amount would be needed. so maybe 3.2 teaspoons (or is it cubic inches?). but you get the idea, a full cylinder will not allow the engine to turn over under cranking. so a partially filled cylinder may. anything over the volumn of the compressed combustible material will result in a bent rod of some magnitude.

it is a tricky little question.

good luck

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

how good are the exhaust manifolds on these cars? I've heard exhaust leaks that sound like tapping, especially when they're close to the head. Hot mainfold + cold water = crack

wires sound more likely to me, though

I've got an 03' S500 in the shop now that was towed in after the owner drove it through a deep puddle. The cylinder compression in the two forward cylinders of each bank is about 50PSI. If the insurance company wants us to tear it down I'll measure the piston-to-deck difference between a bent vs. non-bent cylinder and post the results. I doubt I'll get a chance though. The motor is absolutely hammering when running, so I doubt the insurance company will waste any money on diagnosis. In the past they've usually just had us replace the engine with a crate motor from MB.

Another thing to consider is the frequency of the noise. Since the crankshaft rotates twice for every revolution of the camshaft, you can use this information to isolate the noise to either the cylinder head or the engine block.

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1989 300 SEL that mostly works, but needs TLC

Yep compression test time, don't run cars through deep water they are not boats.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Compression test 145 except for #3 120. However, believe this is existing problem as plug wire hard to remove, some tears in rubber and the plug was hard to remove and replace due to thread damage (not cross threaded but not sharp either.)

Tapping noise has decreased considerably, can barely hear it. Does seem to coincide with two stroke movement.

Used amplified stethescope with no results.

Drove 20 miles at 50 - 80 with no obvious ill effects .

Thanks,
Tom

I don't want to sound like an alarmist, but I'd be a little leery about driving the car without making sure there's no internal engine damage, and I'll tell you why. Earlier this year I had several cars in the shop with water damaged engines. This is quite common after heavy rains and local flash flooding. One of the cars was a 2004 E320. It appeared to have been one of the lucky ones. It had some water in the air filters and MAF sensor, but that appeared to be it. The parts were replaced, the oil and filter changed, and the car was driven about ten miles. The engine ran fine, was quiet, and no fault codes came back. The car was returned to the owner and that was that. A month later it came back with a connecting rod sticking through the side of the block.

If you've been thinking about replacing the head gasket that you've been putting off for awhile, now may be a good time to do it. That way you can check the piston-to-deck height.

One last thing to add. I've had a handful of cars come back several weeks after we've performed water damage related repairs. The catalytic converters were damaged and set the fault codes for Cat. Innefficient/P0432.