mmullany@xtra.co.nz

Somebody please help me! Although I am exploring a swap to an SR20, My current engine an A15 has problems. Last time it was in it would continually blow the head gasket, but worse than that it also kept blowing the rear main seal out.
The engine is out at the moment and my engine reconditioner has 'o-ringed' the bores for me so hopefully that's sorted, but after checking seal crush and engine breathing we can't find any reason for it (the odd thing is that although the block breather was clear nothing ever came out.

Any assistance would be greatly appreciated !!!

This can't be the first time this has ever happened- please help

hey matt welcom to the club you wouldnt happen to own a red 1200 coupe do you as i live in chch as well and have seen it around

rally-a-coupe,

Thanks for the welcome, this is a great site (i've never seen so many great Datsuns)!

No, I have a white Coupe that is off the road at the moment.

I'm sure I used to see yours parked near Miles Toyota?

Just so you know we care.

Sorry I don't know why you are blowing out rear oil seals.

Blown Headgaskets are either caused by head warp, incorrect head bolt torque, Or cheapo gaskets. The head warp can also be induced by hooning about with no water in the radiator/engine.

Can you tell me why my old CA18DE used to break high tensile bolts that held the engine mounts to the block? Maybe it's just another one of those mysteries..

Welcome to the club. This really is one of the best car sites on the net. I can't go a day without visiting.

Maybe it would pay to put a crankcase pressure guage in the cabin, an old Turbo Boost Gauge would do the job.

Chris.

two thing that could cause this is
1: stuffed ringes where on the compression stroke air is slipping through the rings and pressureising the crank case and causing the main seals to pop out
are you still running a standard carb ? if so this could be your problem
2: a blocked PCV valve( positive crankcase ventilation) this is located on bottom or carb there is a breather hose that leaves the block and goes to the carb if this blocked this will also pressureising the crank case

i dont think anybody has seen my car on the road yet as it has been off the road since july 2001 and it was red till i painted it you probally would have seen allen taylors car as his is a simlar yellow

dattodude & rally-a-coupe,

thanks guys you may have put me on the right track,

although my engine was fresh when these problems occurred I fear maybe the rings didn't bed-in properly and that may be the cause of the rear seal popping out,
I swear nothing ever came out of the block breather but as dattoman suggests i will fit a guage of some type,
i will also add another breather where the fuel pump blanking plate currently resides,
i am sure it's not the PCV valve at fault as i don't run one ( i run twin 40 DHLA's)

what have you done with the sump breather and rocker breathers though, if the sump ones blocked your sump would pressurize

You said "kept blowing the rear main seal out" is this just an oil leak or does the seal actually move away from the seating?

If it is just an oil leak, have a close look at the seal. You should find two of the corners that seat in the block have a little 45 degree chamfer on them (about 1mm X 1mm), when you assemble your motor, if you dont place some silcone sealant in these they make fantantic oil leakers (dont use that aviation sealant as it takes a long time (10 days) to harden and it tends to flow out of the chamfers before it has time to harden).

Micko

The whole seal actually pops out, till it hits the back of the flywheel.
This happens within the first run of the engine after fitting a new seal.
In the end I got #$#%ed off and siliconed the seal in which resulted in the seal staying put but the oil was just pushed past the lips

(pressurized crankcase?) (why nothing from crankcase breather which is/was clean and clear?)