Bong!

[nmacc]

Hi folks, I'm tentatively posting in the Engine forum as I suspect my problem may be exhaust-related.

Now I'll admit that I'm being lazy here, I should crawl under and check this out before bothering folks, but I've been a tad under the weather for a week or so, so I'm taking the easy way out.

As my 93 220TE has done a big end bearing

, I've had to source another and I picked up a 93 220TE in Bristol last week. It's better than the original with 57k less on the clock, so I'm going to keep her.

She has an exhaust blow which will need sorting for the test, but she also makes a very strange noise. About 20 seconds after turning off the engine she makes a very loud BONG from the rear; it also sometimes does this about 30-40 seconds after first starting and pulling off, but it seems to be quieter .

Initially I thought it was the SLS as it first happened when I had about 250kg in the rear, but it also happens with only the driver on board. I don't think it's a vacuum in the fuel tank as the cap behaves normally with it's usual 'psst'.

Any suggestions from the collective expertise?

Thanks

 

[grober]

Broken rear spring put under pressure as self leveling suspension settles? AFAIK they are slightly less robust then the non SLS variety. http://www.detali.ru/cat/oem_mb2.as...+++717.413&CT=F&cat=44R&SID=32&SGR=135&SGN=03

 

[nmacc]

Broken rear spring put under pressure as self leveling suspension settles?

I thought we had a prize winner here, but I've crawled underneath and the springs seem fine, although it's a lot rustier under there than I would have expected given the almost pristine bodywork.

Unfortunately other parts are not what they might be either as, having put 550 miles on it since the purchase, I've just found a nice case of salad cream in the expansion bottle.

Not my day really.

 

[grober]

Its sometimes very difficult to see a broken spring. They often break just where they sit on the suspension arm. Best to check by removing the wheel and jacking the car up to allow the suspension to "droop" That way you should get a good view of where the spring sits on the arm. Emulsion in the radiator expansion bottle can be bad news vis a vis the head gasket but really depends on how the coolant has been maintained. Have a look under the oil filler cap and check the oil for thin "wisps" of white in the oil which will probably be pretty black. A sensitive test is to use an exhaust gas analyser to sniff for combustion gas in the coolant once the thermostat has opened.

 

[Bobby Dazzler]

Sounds like a broken spring to me too.

 

[johnsco]

About 20 seconds after turning off the engine she makes a very loud BONG from the rear; it also sometimes does this about 30-40 seconds after first starting and pulling off, but it seems to be quieter .

As you describe it as "a very LOUD bong", it sounds like a spring.
Some badly-fitted exhausts can cause lesser bongs due to thermal expansion and contraction when heating up or cooling down.

Run the car up on ramps or blocks, and stick your head under the rear end.
It should be apparent where the noise is coming from.

Cheers
Johnsco