MX5Ireland

have 93 mx5 here 1.6 eunos .I fitted a powder coated inlet manifold(supplied by customer,) but noticed coolant in inlet port of cyl 3 and 4 .I tested compression and it 1. 50psi 2. 5psi 3. 5psi 4. 25psi. Car drove in what seemed perfectly with no issues.Any ideas.I have checked timing belt just in case it jumped/slipped. Conrods are all coming up equal amount.

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No , is it important to have throttle wide open?,Is it ok to have all 4 plugs out while doing compression test.? I am going to do coolant pressure test today to confirm no water getting in to cylinders, with the plugs out and I have Borescope here so I can have a look on pistons for signs of coolant getting in and then, next option, fill the cylinders with diesel/petrol mix and check for leakage..I have heard of wet compression test but not sure of much oil to put in cylinders beforehand.People say small amount??But any ideas ? Will the oil not get in to compression tester/gauge etc . My head is melted(me not the car) with this one as it drove in no obvious issues but when I drained the coolant there was only approx 5ltrs in it



I also checked conrods height and they are perfect.Timing belt was fine and I removed and refitted correctly to be sure including checked the keyway (LNC engine JDM 115bhp)

I also towed the car in case hydraulics lifters had drained out etc.



I am thinking maybe residue sand in the powder coated inlet manifold but I blew it out with airline before fitting.Mad situation !

Thanks, extremely low and it drove in no probs.I fitted power coated inlet that customer supplied and now I am thinking residue from inlet has fooked the rings,but surely not all etc

Car drove in with no issues.I was fitting 6 sp box and fitting powder coated front suspension arms but customer decided to get inlet manifold and cam cover done also.I removed inlet mani and found coolant in the port of 3 and 4 cyl.Presumed it may have leaked in while removing manifold. Would not start afterwards so stripped timing belt to confirm belt had not jumped.It was perfect , with no teeth missing ,so refitted it using correct marks etc.Keyway is fine also as its LNC crank and no damage to crank or keyway or drive belt pulley itself..Done compression test , results above. Baffled .Removed inlet manifold again and got new gasket incl some Dirko around both water ports on the manifold.Torqued up all bolts etc.Still no compression.Done dry AND wet compression test showing no difference with either. Still showing 25psi at number 1 , practically nothing at number 2 and 3 and maybe 15psi at number 4.Today I lifted cylinder head off and bores look fine as do piston crowns,all pistons level so no bent conrods etc. I done petrol test on valves , while head upside down obviously, and cyl 2 and 3 leaked quite quickly..I closed 1 and 4 by spanner and seemed to hold petrol lot longer but I am still not convinced that 90% of the compression loss is down to valve leakage seeming car was fine only last week.I am at wits end with this one.I have few mates who are mechanics so one advised head off and get valves checked properly other says it cant be valves that bad to cause such problems.No side slap in the pistons so presuming rings are ok otherwise there would be sideways movement in pistons and the bores themselves are nice and polished with no scratches.Minimal if any wear "lip" on the top of the bore as it mint engine previously with great power etc no oil or water loss that I know of and verified by owner etc.As above the only thing I noticed originally that there was only approx 5 ltrs coolant when I drained it on day 1.I also done water pressure test at 14lbs today , with Sykes Picakavant tester, and ze

Yes I have spark and yes its mk1 so CAS is plugged in but its compression issue.I think lifters/etc.I

done the old trick of pouring some petrol in to cylinders and it draining after approx 30 minutes which is not bad as petrol is very light viscosity but now I have put some Diesel in about 7pm and its holding fine. My mate came around and we put petrol on the valves with them closed and it seeped out big time..I am fixing cars for years for myself mostly and parts etc as you know but the petrol emptied very quickly (maybe 1 minute) and came out the inlet and exhaust ports obviously as head was upside down of course. I am not fully sure of my next comment but is the back of the cam lobe the fully closed.I know the lobe is the fully open position but is the rear fully closed or is there more than I closed position on the cam ??(like the sides of the lobes?.I think lifters are not closing fully ie carbon build up maybe?I had this issue years back with few Mondeo,s and Vectra,s where customer had been using incorrect oil and the oil was not getting to hydraulic lifters .I can see the "buckets" moving on the cam lobes etc but not sure if the inner of t

Yeah, back of the cam is fully closed. If you take the cam out of the head and the valves then hold the petrol then it's the lifters if not it's the valve seats.
The lifters clean up really easily with brake cleaner if they are gunged up. Only tools you need to recondition them are some long nosed pliers and brake cleaner.

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Ok so good news.I left the cylinder head in to machine shop and while I was there they vacuum/suction tested each inlet and exhaust port and there was very little vacuum, ie valves not sealed , on 6 of the 8 ports.They advise cyl head had overheated (see early post re only 5 ltrs coolant in the car when it first arrived).Valves seats etc warped and not sealing.Eureka at least fault found.Side note there was also small "crystallised" particles in the valve seat which I can only advise cam from internals on newly power coated inlet manifold(sand most likely).Although it was blown out several times obviously there are areas where inlet manifold wont clean fully.Moral of the story dont powder coat your inle manifold.!!

ouch! Was a new head required or new valves + a valve seat grind?

Removed head and got it tested , needs reseating of 16 valves , new stem seals, few guides and skim.Hopefully that will be it.I will know more on Tuesday maybe

Got cyl head back fully recon, new valve seals, regrind all 16 valves/seats. skimmed and all 16 hydraulic lifters cleaned and freed out.Got car running again ,great job.Sand in the inlet manifold does not really do any good......

Oh dear ! What was the result of the sand in the inlet ??!

great stuff, is that kind of refresh big money?

Sand causing valves not to close etc.Recon head and gaskets,oil, filter and few bits 800e.

Sand causing valves not to close etc.Recon head and gaskets,oil, filter and few bits 800e.

Going like a rocket, with new head, Cusco induction kit, new timing belt, red cam cover 52mm alloy rad and red slimline fans, 6 speed gearbox, powder coated front wishbones ,painted anti roll bar (red) and set mk2.5 shocks all round.Great job and comfy to drive, slightly high riding maybe but very nice.Better than the crappy coilovers that were in it !