306 diesel - throbbing sound

Jan 29, 2004 7 Replies

Going home last night I got stuck in the traffic like everyone else



While the car was on tick-over it started to throb (best I can describe it)



When I revved it, it didn't shudder/stutter like I was expecting, that sounded fine, but just continue to throb (shook the whole car). Did this for



60 seconds each time

Does this make any sense to anyone?



Had been driving for over an hour and temperature of the engine was normal...


Sounds like the governor caused the tick over speed to drop to low, unless it happens again don't worry.

There could have been snow/ice stuck to the cooling fan which would cause an imbalance when the fan was running while you were in traffic.

-- James

Sounds like that could be it Batman! As I had loads of ice built up on the front of the car last night

Cheers

I bet this was caused by the radiator fan coming on. You already say the motor was warm, so you stop in a line of traffic. The radiator heats up as air isn't going through it any more, the fan starts up and loads the aletrnator, slowing the engine down fractionally. Thsi producs a "throb" that you're not used to. If not this - the same could happen with the Air Conditioning compressor.

My Xantia was doing the same thing, except it's got two fans, was a little worrying at first until I realised what it was.

-- James

He said it continued when he revved the engine, i.e. could not be caused by the engine being slowed down.

Also, it could not be the air-con compressor since the external moving parts move all of the time, and on this engine when the air con comes on the idle speed is automatically sped up to ensure smooth running.

-- James

Dunno whether the Pug is the same, but I had a ZX (same engine) with the same symptoms. Turned out to be a hole in the "resonator box" (looks like an oil filter on the underside of the exhaust manifold) my advice is, if its buggered, get quick-fit et al to fix it, bugger of a job...

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