what could cause the oil cap blowing off a freshly built bottom end with rebore new rings ect new head gasket ect ect. in boost the cap blows off. checked compression and there all the same in each bore. could the head be to blame or any sugestions welcome.
juffer

 

if its only when the turbo is boosting!! you need to check all the breather's and pipes that go from inlet manifold to engine..dont really think the head will be the problem..

 

Checked breathers and there fine. It has a new cap. What sort of pressure builds up on a new engine? It was rebuilt 2000 miles ago. I have done a compresion test and its 8 bar across all pistons. ( running a stage 3 head with 57 cc chambers and forged pistons in a 2.1 zvh)

 

what boost you running mate, mine does this also, similar spec jus lower compression.

 

It happens alot with all cvh's turbo and non turbo.

 

I suppose it's possible that the cap was stripped or broken, or that it's particularly hard to screw on in this vehicle. But if not, the only explanation is that it wasn't tightened all the way.
___________________________
Hang up and drive.
Autopartswarehouse will help you.

 

..??

they are a shitty push fit on the CVH,

Orderd a Steel one from ebay, twin O-ring seal with a grub screw to secure it when its fitted.

 

-ok So Where Do You Think The Pressure Is Coming From!!
Compression ??? -----------anything Else?---
Whats Attatched To You Rocker Cover That Might Be Giving You So Much Pressure??
Not A Lot Left Now To Blame .

 

Something must be a miss, you dont see the big power boys having to secure their oil caps down. I know they are only push fit but thats all they really need, it must be blow by or something like that, have you had a leak down test done?

 

not done a leak down test. The breathers were checked and replaced. New cap was fitted. The compression test was fine showing a stable level of compression in all cylinders. The other thing that is happening is when i shut off the acceletator after a good sprint there is blue smoke coming out the back. only when shutting off tho not on acceleration.

 

Right well........that sounds like the turbo is well on its way, and if its letting oil pass on over-run, you can almost guarantee its letting boost pass into the oil/breather system when you're giving it some beans!

So i would be willing to bet my jam tart thats your problem.

 

Tthankyou safe chave. I was dreding sombody telling me that. Its a stage 3 t3 any owned from new for 3 years but only covered about 4000 miles. so waranty will be no good now.I had the turbo off recently and there was no play in the shaft at all but i still take it that the bearing may be fine but the seals are no good.

 

Well, for a 4000 mile turbo it seems unlikely, but on a fresh engine and the symptoms you've described it cant be much else.

See if you can borrow a turbo just to try and prove the fault, the last thing i want is for you to fork out on a new turbo and have the same fault, but until you try another one you cant get a definite answer.

if/when it comes to buying a new turbo step gap seals are the way forward

 

looks like i have some reasearch to do on seals.

 

not really, theres standard and theres step gap, any half decent uprated turbo now should have step gap seals as standard anyway

 

mine was from turbo technics at Ł650 so i hope they have used them. i will try a turbo and see if that solves the problem. I dont have oil in my boost pipes.

 

it'll be the exhaust side leaking to make it smoke.

Turbo Technics don't sell shit, i would be very surprised to see one failed at such a low mileage but then if its been subjected to oil starvation at any point it will never last long

 

is there any visual way i can see if it is gone? also as you are good on wires what are the colours for the amel valve an a series 1 as sombody cut mine in the loom. Could you please explain how to do a leak down test. Thanx for replying to my questions

 

tbh honest mate on a newish engine your seeing 116 psi which i believe to be poor, most engines should be around 150, so id be likely to do another compression test and put a spoonful of oil down each cylinder and see if the compression raises, im thinking poss rings

 

just curious, why would the turbo seals be making an oil cap blow off? surely thats down to crankcase pressure if the breathers are changed? he does have low compression on all 4 too

 

wot breather are you useing on your zetec bottom end? i take it you have blocked the frount one have you relocated it to the bake of the block?

 

if the seals are shot then they are going to let boost pressure pass into the oil system, are they not............

 

WOT SEALS? do you mean piston rings?

 

tbh may well do, im not 100% sure of that, but i personally think his compression is very low which could poss indicate rings (not saying your wrong as ive never experienced tht to know) but id try a tea spoon of oil down each cylinder then do another compression test and see if compression raises? just incase this is it it doesnt cost anything to try?

 

Safe chave you were right in saying my turbo was rhubarb!! It finaly went and there was unburnt oil in my exhause followed by smoke which i can only explain as the red arrows were behind me. I took the turbo off and the play in the shaft was now pressent. The bearing must have gone and the wayit moves i would expect on a 70,000 mile turbo. How hard is it to recon yourself or how much am i expecting to pay fora proffesional to do?

 

i rebuilt a turbo once it was a bit tricky but went bace 2gever ok but saying that it never worked lol

leave it to the professionals

 

the fucking OIL SEALS in the turbo!!!!!!!!!!

 

They aren't always salvageable, depends how far gone they are.

its probably just easier all round to chop it in against a new/recon one.