Mk1 engine knocking

[Carlos]

We've got a really bad knocking noise coming from the engine in our new mk1. It starts when the engine has warmed up and you rev it over about 2krpm, and gets progressively faster with the engine.

The car runs fine, but just sounds horrible and is starting to worry me! Any ideas of what it could be?

Cheers

Carl

[PW@Woodsport]

its most likely to be a worn bottom or big end bearing which is pretty terminal im afraid...it costs to much to repair this versus fitting a new engine with a fresh lifespan ahead of it.

On a plus side though,dont discount that it could be massively overfuelling causing the knock,run a diagnostic check.....it will possibly throw up a code 4,EFI temp sensor...but this is clutching at straws.

If its only knocking under light throttle id say bottom end though.

[Carlos]

Doh, I was hoping I wasnt gonna get a reply saying something like that!

So much for getting a nice new MR2 we wouldnt have to spend any money on! Wish I'd kept the gold one now, could have stolen the bottom end off that as it had been overhauled by Chris

[sadako]

Fear not! I got a new engine with less than 40k on it for £560 with vat. You can get a engine with more miles on it for peanuts and it needed about 200-250 quid to fit it. This is what I did and it has worked out mostly well so far apart from some unrelated electrical probs.

ed- fixed the electrical probs now apart from some loose connectors with no obvious place for them to be connected to

[Carlos]

Well the engines only done 94k, and a while back it had a complete topend rebuild around 80k miles (although it was 6 years ago), so would it be worth trying to fix it? I've got no problem giving it a go myself, but if the parts are going to be as much/more than a new engine then i wont bother.

Out of interest where would you recommend getting an engine from? Fensport?

[LimeyMk1]

I know of a couple of low milage engines that might be for sale down the road from you Carlos. I'll check on Saturday for you if you like.

Chris

[Carlos]

That would be great if you could. Thanks a lot!

[PW@Woodsport]

carlos dont rule out the overfuelling as a cause just yet.....you never know.

[LimeyMk1]

Indeed, changing the engine is not a fun job. Do all your peripheral checks first before signing your lower back away!

[Scooter]

its most likely to be a worn bottom or big end bearing which is pretty terminal im afraid...it costs to much to repair this versus fitting a new engine with a fresh lifespan ahead of it.

.

paul, aren't the big end bearings replaceable by 'just' dropping the sump and undoing the conrod(?) bolts.........

If so, Carlos, i have some shells from a engine i removed from a rusty (but quiet engined) mk1 if you fancy giving that a try?

[Speedy]

I don't think it's quite that simple - and please correct me if I'm wrong - since if it's knocking, then you've got an out-of-balance end, which will be rubbing against the crank. From previous experience of an engine which used to blow ends all the time, you end up with the following problems :

- Crank (journals?) end up getting scored and damaged, requiring a grind, or new crank. I would have thought that taking the crank out is a sump off, gearbox off job. I don't know if you can do that with the engine in the car - you probably can, but given that you have to put it all back together again, it must be easier to do it with the engine on the bench, upside down.

- If it's the end of a conrod, then you can heat those up, where it's not getting enough oil, or from banging around. These can go oval, instead of round, causing further damage to the crank etc etc..

- The bits of the bearing which failed are still in the engine somewhere. If your really, really lucky, then they are in the oil filter, or in the strainer at the bottom of the sump (if there is one on the 4AGE). More likley, they are floating around in an oil channel somewhere, restricting flow.. not good. We found the only solution to this is to strip the block and blow it out with compressed air, but we were working with a much smaller engine.

Hope you get it sorted soon, can't have WMC thinking that mr2s aren't solid!

[PW@Woodsport]

yes just as speedy says,its not that simple plus ive found it financially unviable throwing money at a problematic engine when replacements are easy to come by....in other words you could fix the knock but how long before something else on a tired engine lets go?

[crazylegs]

i`ve tried the method of just replacing the bearings with the engine in situ.its not that straight forward.if ,and a big if, your crank is not damaged then you have a chance.you must remember the bearings may not have been a standard size as they came out of the factory.there should be some numbers stamped into the block on one corner ,a series of 5 numbers .they are either 1,2 or 3 for each main bearing cap size.
you then have the con rod bearings to think of,as this is where the problem will probably be.again the crank must be damage free and round,if its knocking badly then this is unlikely.if it checks out the new bearings must be exactly the right size.any slight error here and youve wasted your time it will knock again in a matter of a few hundred miles.
just to add another spoke ,why did it fail to start with? its generally oil starvation that causes it. this problem will still be there even after the change.
so £150 for bearings and the chance you will get it wrong/it will reoccur or £250 - £500 for a replacement engine. i`d go with an API engine every time.the swap is not really that hard.

[Carlos]

Well its gone to Millway in Andover and they say its probably the shells. They did a compression test to make sure its not something like a broken piston and that all came out ok. When the MR2 expert guy comes back from holiday in 2 weeks he's gonna take the sump off and and check it all out. If its repairable he will, if it'll work out too expensive we'll start looking at replacement engines.

He seems to know his stuff so we'll leave it with him and hope for the best. I know my other MR2 had the same thing done before I got it and in the year I've had it its run sweet as a nut, so hopefully it'll be a similar story for this one!

Cheers for the advice everyone!

[adamh]

i guess a s/h install is a good option.. then get your one on the bench and build it, cheap as chips.

Watch out for API though, there gearboxes are not tested, bull, mine blew within 12 weeks cost over 250. Maybe their engines are slightly better