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We have an na6 which has a slow oil leak, took it to a local mx5 specialist, who advised that it looks like the leak is coming from the back of the engine between the head and the block. Looks like the car may of overheated once in its lifetime causing this to start. They also advise that it looks like the rear main seal is on the way out as well.

Was quoted 1400$ to take the engine out and take the head off to replace the gasket and inspect the engine, and rear main seal. Also said they'd probably replace the sump gasket while the engine is out.

Now I know with something like this that price depends on what is found, but is 1400$ a reasonable amount to perform work like that? I wouldn't of thought you would pull the engine out to replace the head gasket, but I suppose if the rear main seal needs replacing I could see why you would pull the whole lot out.

Just after peoples thoughts, and if anyones had similar work done?

Thanks.

I'd get a second opinion....take it to a sponsor if possible
Oil leaks are normally the cam cover gasket or cam sensor
If head is warped it is more likely to leak water and/or run poorly
NOT leak oil

First try replacing the cam angle sensor (CAS) o-ring. On the NA6, it's on the driver side (RHD) rear of the head (near the top) & leaks oil when it needs replacing:
http://www.miata.net/garage/cas_seal.html
http://www.miata.net/garage/cas_oring.html

Thanks for the comments, both the cam angle sensor and cam cover gasket were replaced already, by another local mx5 specialist. The shop we took it the second time is also an mx5 specialist (different shop).

I regret to say that not all MX5 specialists are good MX5 specialists. Add your location to your profile and we'll be able to point you towards good ones in your area.

New cam sensor o-rings often leak if the job is not done properly (actually very, very often to be honest). It's not normal for the sump gasket to leak - for a start there is no gasket, just a silicone seal, and it's usually pretty good. The engine does not normally come out for an oil seal replacement, nor does it normally come out for a head gasket replacement.

CeJay wrote:both the cam angle sensor and cam cover gasket were replaced already

In that case, assuming either are not leaking again as MB says, then it sounds to me like you're being quoted to cover all possibilities, however you're paying for the prerogative. Rear main oil seal requires gearbox to be dropped, or if all the other things were being done, then you could remove the motor, but it sounds like a sledge hammer to crack a walnut. Given it's a slow oil leak you could also live with it.

OP is in the ACT I believe.

I'm in the ACT

If it has overheated and you have a leak. More likely than not the head is warped. There is more to the story than what is in front of you.