16 replies to this topic

[chris2009]

I was driving my car home last night when I stopped past my mates house and when I drove round the corner to go home there was a really loud compression sound like the head gaket had gone but was still running completely fine no lose of power at all and had just recently had the head gasket changed. I didn't get a chance to check this morning being very late for college and on the way the sounds kept getting louder and losing more and more power. Now it litterally produces such little power it almost stalls pulling away. When i looked under the bonnet it sounded as if it was combusting back out of the air filter. The only reason i can think that would be causing this would be a burnt valve and one of the valves isnt closing fully. Any other reasons anyone knows why this might be happening? I have been running it on unleaded with no additives as i was never told that this was the case with minis.

Cheers for any help in advance

[998dave]

How's your experience with mini's? I'd start by pulling the plugs and seeing if any stand out as 'wrong', consider also lifting the rocker cover and look at the rockers and valves movements, (rock the car forward and back in gear with plugs out).

The comment on being very low on power suggests more then one cylinder is having a problem though, what does the dizzy look like? is the timing still about right?

Dave

[998dave]

Also, if you've got a compression tester it may be useful to give that a go!?

Lastly, even if it is a valve or hear issue, don't worry too much, it's not too major a job to change a head on a mini, or re-lap valves, (in fact doing valves can be quite therapeutic).

Dave

[mk3 Cooper S]

Burn't valve feels like it is running on 3 - which it is!!

[chris2009]

Its runs relitively normally at idle and a slight bit of throttle but when you actually put it in gear and try and pull away it seriously bogs down and the noise comes on. It also makes the noise when revved up higher. My expierience with minis isnt that great ive only owned one since may but my car knowledge and experience is quite good as im studying motorsport. This problem has come on so soon and developed so quickly as in within 4-5 miles of driving would something like this develop this quickly?

[chris2009]

Also if i drive it home am i going to be casuing more damage as i really dont want to leave it at my college over night i would rather it be at home.

[datsun100a]

sounds more like a timing problem

[mk3 Cooper S]

Air leak causing lean running.

Check the manifold gasket for leaks.

[liirge]

Air leak causing lean running.

Check the manifold gasket for leaks.

was thinking that. as well fits with the not being able to rev as well.

[minidaves]

blown headgasket i recon

dave

[chris2009]

The head gasket was only done about a month ago how could it of gone this quickly and it doesnt sound like its running on three. When i checked the vaccum advance i pulled the hose off and a small puff of smoke came out of the nipple. the only thing i can explain this with is would be ehaust gases. Meaning an inlet valve is open at the wrong time causing exhaust to come back up through the to the carb which is where the noise its mostly coming from. im hopefully getting a trailer to go and pick her up today. Shes been left in a car park overnight hope she all still there.

[chris2009]

Also would running unleaded on a 86' mini cause a burnt valve when did they change the heads to unleaded?

[mk3 Cooper S]

It could do but so could badly adjusted tappets?

With the car running at idle ger some wd40 or simular and spray it around the manifold to head joint and the nmanifild to carb joint,
Check to see if the tone of the engine changes.

[WiredbyWilson]

Also would running unleaded on a 86' mini cause a burnt valve when did they change the heads to unleaded?

if the head is a leaded - non-cnverted item then over a long period of time yes a valve can burn out.

Sounds like you need to do the above test to elliminate any air leaks, and if not then it's time the whip the head off and inspect again.

[mk3 Cooper S]

Also would running unleaded on a 86' mini cause a burnt valve when did they change the heads to unleaded?

if the head is a leaded - non-cnverted item then over a long period of time yes a valve can burn out.

Sounds like you need to do the above test to elliminate any air leaks, and if not then it's time the whip the head off and inspect again.

Worth doing a compression test before you whip the head off IMO