12 replies to this topic

[FirstThingsLast]

I noticed yesterday, after a short drive, My Sprite 1275 has developed a loud rattle/knock from the engine/engine bay. When I popped the bonnet there was an oily smell & when I opened the oil filler cap, a fair amount of white/blue smoke came out. The engine knock isn't constant, it takes around 10 minutes to start and only does so when the car's under load and at low RPM (1500-2500).

 

Any suggestions on what I could be looking at?

 

Cheers, Ben.

[jaydee]

Do a compression test

[Nick Warwick]

Have you got oil in it?

 

video will help out loads

[FirstThingsLast]

Have you got oil in it?

 

video will help out loads

 

Yep, there's plenty of oil in. I'll try and get out tonight and record a video.

[Cooperman]

Very hard to diagnose without seeing and hearing it.

 

If it is blowing smoke out from the oil filler cap at tickover it means that there is crankcase compression. Combined with the knocking this could be a head gasket (HG), cracked piston, a broken piston ring(s) or a combination of problems. 

 

As JD says, do a compression test and, if possible, a leak-down test. That will isolate the damaged piston or cylinder, unless it's a HG in which case it will identify which 2 cylinders it is blowing across.

 

After that the next step will almost certainly be to remove the head to check the HG and look down the bores. It may well be necessary to strip the engine for repair.

[FirstThingsLast]

Recorded a little video, you can't really hear the knocking as the car wasn't under load, however, I think there's something that doesn't sound quite right?

 

 

[Ellie]

Sounds same as mine, well very similar....
Got me worried now.

[69k1100]

Or piston slap. How many miles has the engine done? Could just be worn out.

[jaydee]

Adjust tappet clearance and see if it goes better, sounds like worn tappets. Typical sintered rockers..

[FirstThingsLast]

Managed to get another video, this time with the knocking far more pronounced. Neither me nor dad are hugely mechanically minded but he thinks it could be the vacuum advance on the distributor. Is it supposed to wobble as it does in the video? I've not managed to do a compression test yet, but I've bought a compression tester which should be here sometime next week.

 

[jaydee]

No it has to be rock solid to the dizzy body and shouldnt move like that, it could alter the timing to wrong advance causing detonation

There must be one or two screws holding it

[gazza82]

When you are holding the vacuum advance still, is it still knocking? Does sound like tappets to me as well.

Edited by gazza82, 24 October 2014 - 03:46 PM.

[FirstThingsLast]

Spent to last few days eliminating various problems. Carried out all usual engine maintenance, set valve clearance & fixed the vacuum advance on the distributor. The rattle has now stopped and the engine sounds a hell of a lot better. 

 

Thanks for all your help.

 

Ben.