Engine playing up --AGAIN!!

[mu0u207b]

Hi everyone. Im having problems with my minor, as usual!! Over the past couple of weeks the car has been running not very happily. The first problem was experienced on the motor coming home from uni. There was a distinct lack of power and a sweeking and rattling noise coming out from the engine. It had burnt up lots of oil and was using more petrol than usual. Investigations led to a blown head gasket which was evident when the head came off and there was oil trails between 3 and 4 cylinders. The sweeking has now gone but still the engine lacks power by about 10-20% approx, there is a slight rattling/pinking noise on initial cranking until oil pressures up and reappears when underload and at pressure down to 35-40 psi. The engine misfires and inspection of the exhaust, shows that on miss fire there is a blackish to blueish smoke- evident of oil. The engine has become more noisier on motorway runs and will not cruise comfortably and quietly at 70mph. Any ideas with these various symptons. Any help would be wonderfull

[bmcecosse]

Sadly it sounds like the engine is in a very bad way ! The rattling is the bearings - and i suspect the rings/pistons have taken a beating. By far the best bet will be to look for another engine - what capacity is it ?

[mu0u207b]

The engine is a 1098 with about 90 thou on the clock. What bearing would probably be causing the problem. The oil pressure on start up is about 75 psi and goes to a steady 40psi whilst warm at idle and about 60 at cruise. There has been no change in the oil pressure with no detioration. The engine bores are sould with no scoring. I noticed when i was cleaning the head whilst it was off that with one of the exhaust valves removes that on the seat there was avery fine hairline crack. Would this make much difference to performance and is it advisable to get a new seat- the head is a unleaded conversion.- Thanks

[bmcecosse]

Ah - well if the oil pressure is ok then there is hope ! Yes a cracked seat means The End for that head - well it could be repaired but not economic sense. Many heads available (check SALE section or ebay) - ideally you want a 12g202 head - same as you have - but a head from a later 998 Mini will go straight on - and will be unleaded. Ok - the inlet valves are a tiny bit smaller, but it is unleaded !!

[Welung666]

I have a couple of 12g202 heads in the garage if you need 1, neither are unleded tho

Lee

[Willie]

Further to your comments on your oil pressure. For a 1098 engine
the start up pressure of 75psi is far too high assuming that your
oil gauge is accurate! When cold the recommended pressure of
60 psi will be exceeded by about 5 lbs only for a short while on
a healthy engine. The high pressure reading is decided by the
length of the Pressure release valve spring which is situated beneath
the domed nut found behind the oil pressure switch,to the rear of the
dizzy. The length of this spring should be 2+55/64" (72.63mm) and it
is NOT advisable to stretch it to exceed the normal max pressure. This
spring should have no effect on the tick over pressure only the max
pressure.

[mu0u207b]

Thanks lee for the offer. The bearings need sorting so the head will be put off for a bit. Have to priotise what work needs to be done. Hopefully my head is salvageable.
I expect the pressure reading is a bit too excessive and probably mainly due to the gauge. May be out slightly. Its probably more in the region of 65-67psi. Any idea on what bearings might be playing up. There is no deep rumbling noise but there is a slight vibration every 3-4 seconds, almost like it is idling unevenly. --Its not a happy bunny!!!!

[bmcecosse]

Well no wonder with the cracked head ! It is not economic to salvage the head - just get another - you have already been offered one ! With that oil pressure your bearings are ok - and don't worry about start up oil pressure - it means nothing ! It's the running pressure at 50 mph in top gear that counts - if it's 50 psi (engine fully up to temperature) you are laughing ! So just stick another head on it - and enjoy !

[mu0u207b]

The exhaust valve has only got a small hairline crack which obviously expands when hot and reduce performance. Would it be cheaper to get a new valve seat machined and replace the cracked one. How much does machining cost roughly. Could i change the seat my self using low tech methods, i.e. further crack the seat to break in two and push fit a new one?

[Kevin]

I think you will find that unleaded seats can only be fitted in a machine shop as they are not DIY, also its the 1st time I have heard of an unleaded seat cracking and as the valve has a crack I would replace that as well again thats unusual. As an unleaded head is around £125 all in I would have thought a single seat cant be much more than £25 and a fiver for the valve.

[bmcecosse]

The risk is the seat will fall out and ruin the engine. Dump the head and fit another !! Unleaded head is not necessary for day to day motoring - just use a standard head. My 12g295 head has been on my engine for 6 years now - ok it's only summer use, about 3000 miles per year - but it gets thrashed most of the time - has never seen leaded fuel or any additives - the valve clearances are all still fine and the compressions are 160/170 psi. This unleaded nonsense is vastly overstated. Just fit another head !!

[Pyoor_Kate]

I would chat to a local machine shop, see how much they quote. My locally recommended one does a full recondition and unleaded-conversion on an A series head for 140 quid (new valves, guides, seats etc...) - so to just replace one faulty valve seat and valve shouldn't be too costly.

And for the sake of keeping an unleaded head it's probably worth it - especially if you do a lot of miles, or a lot of motorway miles.

I'm slightly frustrated that I've put on another leaded head, but I'm thinking I'll save up and get it recon'd and converted to unleaded later (unless I spot a nicer 1275 head that's unleaded going anywhere!).

[rayofleamington]

unless I spot a nicer 1275 head that's unleaded going anywhere!

I have one which I have not got round to using yet - too many other jobs on the go
I was going to use it on the 1098 in the traveller but decided not to yet as the traveller engine seems a bit rough anyway, so not worth upgrading it - best just to change it. I won't have time to change the traveller engine for a good while so if you need a 1275 unleaded head, gimme a shout.

It will need a bit of work as the thermostat housing bolts need changing and the hole for the heater outlet needs opening up.

[mu0u207b]

I expect that i will change the head as ideally the valve guides should be replaced and the head skimmed so i may as well get a new one. Probably have to put it off for a bit tho- only a student so have to earn some money over the summer hols!! The present head has done about 30-35 thou miles in about 4 years, and have had quite a few problems with burnt out valves, broken springs coked up cylinders and blowing gaskets. All in all the heads probably been off the car about 7 or 8 times- would having the head off this many times and having to undo and do up the nuts many times have caused the head to warp slightly?? Obviously that many times is not ideal. This may, if true, explain rescent problems- see my many postings on the forum- there are many!!!

[turbominor]

I have one which I have not got round to using yet - too many other jobs on the go

thats a good head!! mg metro (non turbo) unleaded, biggest prod valves fitted to an unleaded head!

[bmcecosse]

Yes if you have had many probs with the head - then cut your losses and fit another. A gasket is only a few pounds - must be worth a go ! And yes - the leaded MG Metro head is a very desirable object !! Second only in value to a genuine AEG 163 Cooper S head.

[mu0u207b]

Im starting to consider whether a good summer job will be to inspect and maybe rebuild the engine. The engine has done 90000 miles. With this sort of mileage what things should be done whilst the engine is out. Crankshaft bearing are all original and showing good pressure but is it advisable to replace them anyway just in case of potential freeplay developing in later motoring. Any other major items should be looked at??

[bmcecosse]

If you are going to strip it - then you must fit new bearing shells on re-assembly (£40). Since a crank regrind is only £40 - it would seem mad on an engine of this age not to have that done. If you pull the pistons for inspection - you will probably find you need new rings (£30 ?) - and maybe new pistons (£ 60 ?)- again you need to decide if it would not be better to go the full hog and just get a re-bore (£40) while you are there. I would certainly take the opportunity to fit a much better camshaft - the MG Metro one (~£10 on ebay)works very well - and in any case you should be fitting a new oil pump (£20) - so if you change the cam you need to get the right one to suit the camdrive. And consider fitting the newer camshaft drive with the rubber tensioner - makes for a much quieter engine. You need a new chain anyway - so investigate the complete new drive from any Mini supplier. A much better inlet manifold is the alloy one from the MG Metro (~£5 on ebay) - and with this a 1.5" SU carb (~£5 on ebay) will liberate a good few extra horses from your engine !

[mu0u207b]

The main crank bearings are giving no problem at the moment so could i fit a standard set of shells to replace the old ones assuming not too much wear. Obviously i would need to get the engine out for this. I dont have any lifting gear- accept rugby player built like arms- so could i strip most of the engine out- i.e head, ancillaries, sump, pistons and by that will the engine be resonably light enough to lift it out of the bay- with one /two people.

[bmcecosse]

Yes - I lift mine out myself (head etc off !) - but first take the front panel off complete with radiator - then build up wood blocks etc underneath the sump - and also support the gearbox - then just slide the engine forward easing it up onto the chassis crossmember - and then lift out from there. But replacing the bearing shells is only worthwhile if there really is NO wear on the crank - so you need to measure it very carefully with a micrometer - and then decide.