Not a happy car

[RobinL]

Absolutely right. The 145psi is relatively low pressure and pressuring up using an external source may bring something to light. In my experience crankcase pressure giving breather issues has nearly always been rings :-(

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[Zep]

Absolutely right. The 145psi is relatively low pressure and pressuring up using an external source may bring something to light. In my experience crankcase pressure giving breather issues has nearly always been rings :-(

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Yes - but I can't help but think that we are missing something here - diagnosis via internet is very hit and miss and I would hate to freak the OP out.

 

[Oneball]

I’d expect low readings if the compression test wasn’t done at wide open throttle.

 

[RobinL]

I agree on the 'internet diagnosis' interestingly easing the history driving to the event all ok. Then it wasn't. So this would logically indicate something broke as opposed to something wore out.
Cylindrical pressures are ok and nothing stands out. Plus rings don't generally break in that way. Long unused engine - yes, full power burnouts yes, but not the use described.
So what can break or suddenly stop working?
It's not just a bit of excess gas, it's blowing oil so a significant pressure build or a possibility is oil not draining back from top end, ?

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[conaero]

I’d expect low readings if the compression test wasn’t done at wide open throttle.

The car programme I watch, WD and Car SOS, both have said to have the throttle wide open when doing a compression test???

Thus this is what I do...is it wrong?

 

[Zep]

The car programme I watch, WD and Car SOS, both have said to have the throttle wide open when doing a compression test???

Thus this is what I do...is it wrong?

No - it must by WOT otherwise the pistons try and pull a vacuum behind the throttle plate and gives false low readings as there isn't enough air to fill the cylinder.

 

[jasst]

Thanks for all the input guys, it is much appreciated, I will get to the bottom of it one day, but it may take a while as I am determined to do it myself, As to the compression test, I removed the throttle body, so no restriction there.

 

[Oneball]

Did you clean all the oil out of the intake system?

Could be that:
The cat has collapsed blocking the exhaust and causing pressure in the crankcase as the gasses had nowhere to go. This has then forced oil into the inlet causing the smoke etc.

You’ve fixed the cat. But there’s still a lot of oil in the inlet hence smoking still exists.

Other side of things is that the oil has been getting into the inlet for reasons as yet unknown and this is what has caused the cat to disintegrate.

 

[Zep]

Did you clean all the oil out of the intake system?

Could be that:
The cat has collapsed blocking the exhaust and causing pressure in the crankcase as the gasses had nowhere to go. This has then forced oil into the inlet causing the smoke etc.

You’ve fixed the cat. But there’s still a lot of oil in the inlet hence smoking still exists.

Other side of things is that the oil has been getting into the inlet for reasons as yet unknown and this is what has caused the cat to disintegrate.

A good point well made, but there was no blockage to my understanding? Or did I miss that?

 

[jasst]

Yeah, gave the intake system a thorough clean, luckily have BMC air filter fitted, so bought the kit to clean that, ran the car up to full operating temp on tickover, and no sign of any smoke, only when taken above 2500-3000 revs did it smoke again, now got to clean the whole system again! knew I shouldn't have put it totally back together

 

[Oneball]

Next thought is, where did the bits of the cat go? Are they stuck in the silencer at the back or somewhere along the pipe or have you cleared it all out?

Another thought - is the oil tank over filling for some reason?

Everything else I can think of has been suggested.

Stuck on a train and bored at the mo!

 

[Zep]

Next thought is, where did the bits of the cat go? Are they stuck in the silencer at the back or somewhere along the pipe or have you cleared it all out?

Another thought - is the oil tank over filling for some reason?

Everything else I can think of has been suggested.

Stuck on a train and bored at the mo!

Again all on the money - the overfilled tank would be a total gotcha but I suspect Jasst knows to check it while its running. Also it was fine when driving and then not which sort of counts it out.

Jasst - let me know where you are based. If I can stop by and offer a helpful word I would be happy to.

 

[jasst]

AT the moment the entire exhaust system is off the car, and I can find nothing blocking it, Funnily enough, Dan the Maserati Master tech of Ftech fame, said his money was on it being overfilled with oil as they are extremely sensitive to this, but as I haven't had to put any oil in since he serviced it last year, I don't think that's a possibility.
Thanks very much for the offer Zep, but I'm down in west Dorset and we don't get many visitors down here, but if your passing let me know.

 

[Zep]

AT the moment the entire exhaust system is off the car, and I can find nothing blocking it, Funnily enough, Dan the Maserati Master tech of Ftech fame, said his money was on it being overfilled with oil as they are extremely sensitive to this, but as I haven't had to put any oil in since he serviced it last year, I don't think that's a possibility.
Thanks very much for the offer Zep, but I'm down in west Dorset and we don't get many visitors down here, but if your passing let me know.

Ah, that is a bit of a schlep, but I will keep it in mind if work takes me that way.

 

[jasst]

Next thought is, where did the bits of the cat go? Are they stuck in the silencer at the back or somewhere along the pipe or have you cleared it all out?

Another thought - is the oil tank over filling for some reason?

Everything else I can think of has been suggested.

Stuck on a train and bored at the mo!

Friend who was following me in his Noble when it happened said there were loads of sparks and flames/smoke coming from the right hand exhaust bank when it happened, cat burning up ? it was the right hand cat that I found partially broken up.

 

[Oneball]

The cat itself won’t burn. But it can glow red hot. I’d guess these are the sparks your friend saw, bits of glowing cat coming out of the exhaust. If there were actual flames from something burning then that has to be either oil or fuel. Same thing with smoke.

 

[jasst]

Guess that was the oil burning off.

 

[jasst]

https://www.eurospares.co.uk/parts/maserati/4200-coupe-2004/engine/blow-by-system-20921

Just been having a bit of a play, to see what's happening. I disconnected all three pipes going to the oil tank, Items 1, 3 and 12 in attached dia, and fired her up, on pipe no 3, the small breather that comes from the plenum, and I can feel suction on that pipe. Pipe no 12 and I couldn't really feel anything on that, perhaps a slight bit of pressure, but connected end of it to bottle and nothing came out. Pipe no 1 which goes to the rocker covers you can feel suction on the end of the pipe, but where that pipe goes on to the oil tank, rev it and oil pi**es out (all over the front of engine as I didn't have a pipe to fit on it to go into a bottle Lol). Now, where that pipe attaches the rocker covers, does anyone know if those threaded unions are non return valves? as I can blow and suck through that pipe, not that I know what relevance that could have, also, where pipe no 1 attaches to the oil tank, it is just an open end in the neck of the tank, which means for oil to pi** out of there, the whole tank must be under pressure, is that correct?

Edit, just had another play, put all pipes back except item 12, gave it a hopefully and oil everywhere, so the oil tank is definitely under pressure, so is this normal?

 

[Zep]

https://www.eurospares.co.uk/parts/maserati/4200-coupe-2004/engine/blow-by-system-20921

Just been having a bit of a play, to see what's happening. I disconnected all three pipes going to the oil tank, Items 1, 3 and 12 in attached dia, and fired her up, on pipe no 3, the small breather that comes from the plenum, and I can feel suction on that pipe. Pipe no 12 and I couldn't really feel anything on that, perhaps a slight bit of pressure, but connected end of it to bottle and nothing came out. Pipe no 1 which goes to the rocker covers you can feel suction on the end of the pipe, but where that pipe goes on to the oil tank, rev it and oil pi**es out (all over the front of engine as I didn't have a pipe to fit on it to go into a bottle Lol). Now, where that pipe attaches the rocker covers, does anyone know if those threaded unions are non return valves? as I can blow and suck through that pipe, not that I know what relevance that could have, also, where pipe no 1 attaches to the oil tank, it is just an open end in the neck of the tank, which means for oil to pi** out of there, the whole tank must be under pressure, is that correct?

Edit, just had another play, put all pipes back except item 12, gave it a hopefully and oil everywhere, so the oil tank is definitely under pressure, so is this normal?

Was there smoke from the exhaust? The tank is not under pressure normally, the amount going in and coming back out are roughly the same so a very small amount of pressure is all it should be. There should only be fumes from the breather so we know the issue now. The pressure is driving the oil into the tank and then into the inlet. The main oil return should be the big pipe from the oil cooler, which goes back into the tank below the breather meaning no oil is driven into the MAF, just fumes. Something is still pressurising your crankcase.

 

[jasst]

yes still smoke from the exhaust