Bent Valve?

aw261174 · Postby **aw261174** » Thu Aug 07, 2014 12:19 pm

Hi Guys

My '94 clubman stopped dead coming home last week, after lots of NRMA tutting I got it towed to the local garage. They've had a look and reckon its thrown a timing belt and because its an interference engine has almost certainly destroyed a valve. They're quoting me 5k for a full rebuild.

I spoke to Mazda who told me its a non-interference engine and it's possible under certain conditions to bend valves.

I'm just looking for a bit of advice really. I plan to keep the car, so i don't mind the idea of an engine rebuild somewhere down the line, but its only got 100k's on it at the moment and seems a bit soon if i can avoid it.

Can anyone confirm for me that this is a non-interference engine, and if the MX-5's have a tendency to bend valves with timing gear problems?

Thanks

sailaholic · Postby **sailaholic** » Thu Aug 07, 2014 12:35 pm

Definitely non interference head (assuming not crazy modified) so won't bend a valve if it throws the timing belt.

Mr Morlock · Postby **Mr Morlock** » Thu Aug 07, 2014 6:12 pm

If it were just a bent valve its repairable and you certainly do not need to spend $5K. If the car has done 100K its probably got lots of life left in it. This is not a big job for a good mechanic. If the timing belt has broken etc its easy to tell with the cam cover removed. If its come up to 100K and it has broken you are going to need to replace belt and usual is also the water pump.

manga_blue · Postby **manga_blue** » Thu Aug 07, 2014 6:27 pm

Find another garage. Everything he said is wrong, especially including the price.

Typically you'd remove the head, send it to a machine/reconditioning shop to get it checked and fixed. 4 hours to remove and refit plus whatever the machine shop needs to do, up to around $500. Factor in another $500 for gasket set, belt and water pump. Otherwise you can search for a replacement NA8 engine, and that'd be under $1,000 plus fitting and you could sell a fair bit of the old engine here.

manga_blue · Postby **manga_blue** » Thu Aug 07, 2014 7:00 pm

Alternatively, after taking the timing cover off and checking that all the valves look like they're working OK, take a chance on there being no valve damage at all and just fit a new timing belt and water pump.

hks_kansei · Postby **hks_kansei** » Thu Aug 07, 2014 8:43 pm

Mr Morlock wrote:If it were just a bent valve its repairable and you certainly do not need to spend $5K.

In the case of a bent valve though it's often more than simply replacing the valve that's needed, often bits of the valve break off and rattle around the combustion chamber, the pieces often ruin the cylinder walls, the head, and the piston crown.

An engine rebuild can quite easily reach $5,000 once you cater for replacement parts, and more importantly, machining.

Luckily though, for the OP, there's a pretty low chance of the valve being bent since as said above, the B6 and BP are non interference engines.
Most likely it's just a snapped timing belt, and an engine rebuild won't be necessary.

It should be a matter of simply replacing the belt, and making sure to set the cam timing correctly.

aw261174 · Postby **aw261174** » Fri Aug 08, 2014 11:35 am

hi

Thanks for all the advice. The guy is pretty glass is half empty, and he thinks it needs the rebuild for exactly the reasons hks_kansei said, but i'm just not convinced it has bent a valve, and they haven't actually looked either.

I decided to take the risk and told them to just replace the timing gear, but i got a call from them last night saying that the timing belt snapped because there was oil leaking onto it from the crank seal and the bottom pulley is seized, and there's a key thing at the bottom that's bent or something and so they are back to saying it needs the rebuild.

Definitely get the feeling there's no way I'm driving that car out of there unless I get a full rebuild done. Problem is they've already spent time on it trying to do the timing gear (or by the sounds of it looking for things to justify the rebuild), so I'm going to have to pay them for the privilege of towing my car out of there.

Funny thing is we've been using this place for a few years now for all our servicing and they've always been great, but now they have a new manager...

Think I'm going to have to tow it home and then find somewhere else to take it, anyone know any good mechanics around pymble?

speed · Postby **speed** » Fri Aug 08, 2014 11:41 am

Perfect excuse to swap motors and flog off the bits from your seized motor as manga_blue suggested

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project.r.racing · Postby **project.r.racing** » Fri Aug 08, 2014 12:38 pm

take it elsewhere.

4sfed5 · Postby **4sfed5** » Fri Aug 08, 2014 7:09 pm

that mech doesnt know what hes talking about....sounds like you have a worn keyway.
any competant mechanic would simply replace the belt and accesories and water pump and do the "loctite Fix" and youll be on the road for like a grand. some mechanics are fuckin dumb...anyone heard of google??? FFS its not hard.
worst case scenario replace it with another 1800 motor..no where near 5K. that guy is taking the piss big time. sh*t how much is a genuine brand new long block from mazda???? i think NC motors were only around 4.5-5K
i remember a guy saying he could get 2.3 MPS long blocks for about 3k...