please help anyone cos ive got a major problem! my poor doris ('88 gti) has been diagnosed as having a worn big end or crank bearing or something which is causing this nasty rattling noise above 3500rpm. this comes as even more of an upset as i only bought her 2 months ago and have already shelled out a grand sorting out worn bits and pieces. basicly my problem is that as i am a student at uni and have next to no money at the best of times, i cant afford to replace the engine or whatever just now and will probably have to wait till i finish uni in 18 months time. the car runs fine but makes me wince whenever i exceed 3500rpm and on motorways this is a real pain. i had also planned to have the engine uprated and reconditioned in the future anyway and also the gearbox but now im faced with doing it sooner due to the worn bearing thingy. the car is in good nick and has done 111k and i really want to hold on to it, but not sure if i should cut my losses and sell it, or go without a car for 18 months, (this would hurt alot)or just get myself into even more debt and get it sorted with a group A head or something. if i do get it sorted, how much is it going to set me back roughly to get the gearbox looked at, and the engine fixed and uprated (im wanting around 130/140bhp from it eventually, providing i stick with the standard block and head) any help/suggestions mucho appreciated!
sometimes if its not really bad you can fit new big end shells,theyre about 25 and a 2hr diy job if that wont cure it ,its alot of money for a rebuild or finding a used engine would be an easier and cheeper way out
need a long term solution tho, if i were to sell the car then replacing the shells would be a good idea but i dont want to sell her!
If the crank is in good nick then fitting new shells isn`t a bodge, you`ll have to strip it and measure it all up, go from there. Don`tdrive it anymore or you`ll just cause more damage. You could have the crank ground and fit oversized shells but I`m not really keen on this method myself.
Keithmac your right about a regound crank being not really any good as onece it's been reground all the hardening on the crank has gone so they just wear out quickly again- i would just stick alump in it that you have heard running at a breaker for the time being as if the rattling noise is that audiable then i wouldnt really bother putting on new shells.
I would rebuild it as it makes sense in the long term if you want to run it for a while. I personally don`t think putting second hand engine in would be a good idea unless you knew the history of it as you could give yourself a lot of work for nothing. Also changing big ends only might not do as the main bearings could be done also. If you do rebuild it is the cheapest option if you can lend tools off someone and it is quite easy as well and will give you a better understanding of your engine and you will know if anything else is needing done also.
I found when I took my crank out that after 140k it had only worn by .001" which isn`t bad . Yes you are right about the hardness but if it has been hardened correctly to start with it should be alright to lose a mm on it no problem.
Personally I'd swap the bearings - the crank could be fine. If you leave it you could end up needing a complete rebuild tho........ for all the price of a set of big ends and the easy job of putting them in, I'd try that first.
Dave, any idea how the cranks are hardened and how deep it goes? Just curious as to how they did it from the factory....
GET A SECOND OPINION. My missus' Polo started rattling and losing power on the M1 so she stopped very quickly (well trained you see !) The AA said it was the oil pump, the garage they towed it to said the crank was shot. I found that the cam belt had jumped a tooth, 30 minute job, did another 10K until she sold it with no problems. Does it do it when the engine is cold and the oil is thick ? If its just as bad it ain't necessarily the bottom end as the thick oil will help quieten it the rattle could be ancillary (cambelt covers, alternator etc etc) Stick your head under the bonnet and see if you can tell where it comes from. If it IS the crank then stick some nice thick 20W50 oil in it and don't thrash it too hard until you can get it sorted. I would be really surprised if a 111K engine has a serious bottom end proplem unless it has been abused. Incidentally, if you're short of dosh, modifying the engine could cost you loads in the long run unless you get it done properly, let alone the insurance premium.
Induction hardening shows a cross section which is what I am referring to if not done correctly it wont be as deep and if it is done to much then it will make it too brittle.
That's pretty impressive penetration (as the actress said to the bishop). Any idea how the VW ones were done from the factory? Anyone else?
