mx5 problems 1.6

tehnzbrad · Post by **tehnzbrad** » Tue Jun 17, 2014 8:25 pm

Ok so my car started miss firing at low revs every now and again and it just kept getting progressively worse to the point it was missing at idle and through out the entire rev range. after checking all the sensors and afm, plugs, coils, leads and timing i decided to do a compression test.. all cylinders are 180psi apart from number 2... thats at 140psi, so i go back and do a wet compression test and all cylinders change to 210psi except for number 2.. thats now at 165psi. so at this point i assume its the rings... but the car has suddenly started using water and there is a tiny amount of oil in the radiator.. the engine has only done 150,000kms and has been looked after. so i take the head off and inspect the head gasket (normally you can see if its been blown etc) and it all appears ok and the only thing now i can think of is a cracked head or bung valves... but if it were valve the compression test would have stayed at 140psi on the wet test... i also double checked rings and they are fine... any one had this problem?

4A-GE · Post by **4A-GE** » Tue Jun 17, 2014 11:20 pm

Oil in water = you're buggered.
I expect all you can do here is replace the suspect bits (anything that moves) and hope for the best, or buy another healthy motor and dump that in.

built4speed · Post by **built4speed** » Wed Jun 18, 2014 12:40 pm

How much oil did you put in? If the heads off fill each port with brakekleen with the valves shut, the one it's weeps through more than the rest is leaking.

Growler · Post by **Growler** » Wed Jun 18, 2014 3:16 pm

Just a thought - It could be a cracked head. You may not see it when its cold but when everything is hot and under pressure it could be leaking then?

tehnzbrad · Post by **tehnzbrad** » Wed Jun 18, 2014 4:56 pm

normal amount of oil, never over filled, the only options left are valves and head is what im thinking, but its never been hot for as long as ive had it, and if it not head or valves i have no idea what it could be..

built4speed · Post by **built4speed** » Wed Jun 18, 2014 5:05 pm

I meant how much oil did you put in when you compression tested it?
The factory head gaskets go soft I've found, you often can't see where it's tracking like you can on a mls gasket.
Check the valves as I suggested, will only take 5 mins.
If it had a head gasket leak that was bad enough to drop the compression, that cylinder would be clean as a whistle.
Do you have a picture of each plug and their corresponding cylinder number?

tehnzbrad · Post by **tehnzbrad** » Wed Jun 18, 2014 5:37 pm

ohh, approx 2oz of oil per cyl, ive check all the plugs, no variation on carbon etc and they arent oiled up, ill check the valves asap.

built4speed · Post by **built4speed** » Wed Jun 18, 2014 5:52 pm

That amount of oil explains why the compression results were so high. How many ml? 30?

tehnzbrad · Post by **tehnzbrad** » Wed Jun 18, 2014 6:43 pm

nah 180psi dry (factory and 210psi wet) so its the usual amount the manual said use like 2oz so i just did that, anyway i checked the valves, the exaust valves leak pretty bad aye, ill take the valves out the see if they can just be ground on the original seats, if not ill get new seats/ head.

tehnzbrad · Post by **tehnzbrad** » Wed Jun 18, 2014 6:44 pm

nah 180psi dry (factory and 210psi wet) so its the usual amount the manual said use like 2oz so i just did that, anyway i checked the valves, the exaust valves leak pretty bad aye, ill take the valves out the see if they can just be ground on the original seats, if not ill get new seats/ head.

mx5 problems 1.6

mx5 problems 1.6

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