HI all

Started pulling apart the donor today a 1.8 mx5. Engine ran fine all the way on the 150 mile journey home, however I thought today I'd do a quick compression test. The readings were 200, 200, 140, 200. So obviously an issue with cylinder 3. Reading the t internet doesn't seem these suffer generally so wondered if any issues had been encountered by the collective?

I forgot to stick some oil down the bore to see if it's a ring issue I will try that tomorrow. Other usual suspects? Head gasket? sticky valve perhaps? I wasn't planning on cracking the lump open but as I'm now turboing it a bit of a refresh wouldn't go amis.

Steve

Did you test at normal engine temperature?

It had been run for 2 or 3 mins if I remember rightly so maybe not fully warm.

Check valve clearances?

Do another test at normal engine temperature and WOT.

Will do. The test was done at WOT. Will let it heat up a bit more tomorrow

Most likely is Bent, burnt or sticking valve, it could be broken rings but perhaps. less likely in this case.

The best test would be a cylinder leakdown test you need to buy or McGiver one of these ebay link leakdown tester £28 and a compressor.

[Edited on 8/6/15 by britishtrident]

Well. With the engine run up to temp ran another compression test today and all seems well. 5 psi difference max across all 4 cylinders. Even when it cooled a little I still couldn't replicate the low compression on cyl 3.

Must have been finger trouble on my part. Anyways thanks for the input guys

Good news. I also had the same low reading on cylinder 3 on my 1.6 until I repeated the test at working temp.