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Diagnosis Of A Top End Problem

528 Views 9 Replies 5 Participants Last post by  snotrag
The never ending saga continues...

Background -

Sunday we had a really good run out, so the engine had had a thorough workout, nice and hot etc. I dont abuse it, but it had certainly been up the upper reaches of the tacho a few times (as it should).

- Car is an early 1.8 Mk1, so fixed timing etc, with the CAS at the end of the exhaust camshaft.

- Engines previously been a strong, smooth engine given its 100k miles (as you expect with these cars.

- Timing belt and all associated bits are less than 10k miles old.

- Car seems to have good oil pressure, its not doing anything different to what it has in the past (I have the 'real' gauge).

- Plenty of good oil in the car, and not burning any.

- Still pulling well, no noticeable loss in power.

The cars picked up a really horrendous noise. Had a few sets of ears looking at it and the consensus its coming from the head, on the exhaust side.

Its rotational, (not stuck tappets, I know what they sound like!), and sounds like a collapsed bearing or something. At idle, or under a really light load (top at 35mph) its not too bad. As you rev it it definitely sounds rotational as you can hear it going in and out of balance as its speed changes.

I'm trying to think how the cams are supported. Obviously there will be a number of oil bearings along there length, but what supports them at the end?
Other ideas bandied about were a damaged cam lobe, or as an outside bet a damaged valve spring or follower... I'm thinking possibly an oil blockage might have caused one of the camsahft bearings to run dry?, or a bearing shell has disintegrated.

Obviously my first port of call is to whip the cam cover off but I cant do that till tonight.

Any thoughts?
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when was the last service out of interest ?
Oils about 3000 miles old max. I can see where your coming from though. If there's nothing immediately springing to view once the cam cover is off then I think sticking some fresh oil in will be worth a try. It's had plenty of regular servicing though in the past 2 years.
i would definately get inside and have a look. without being able to hear the noise a diagnosis is very difficult but i think you are starting in the right place anywho.
A gone Crank bearing can deceptively sound like the noise is coming from the top, is it a clacking noise under load, not ticking like tappets?

One of the guys on here found a screw inside one of his cylinders, after having knocking noises, so it's worth having a good investigation!
I've got a video on my iPhone just need to work out how to upload it, I think I can send it to my flickr account.

To me it certainly does sound like it could be a bearing - and your right the sound can travel and be deceptive. Certainly with the bonnet closed there's a lot of sound coming from below too.

I'm fearing the worst....not my month this!
It would be worth whipping the accessory belts off, just to confirm it isn't the water pump or other accessory pulley. (Assuming you haven't already done so.)
Good idea, I'll try that first tonight before the cam cover. PAS pump is the nearest one to where the noise "seems" to be emanating from. It's bloody loud though.
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