Anyway of testing if i have a blown inlet manifold gasket

[angel]

Hi all

If you were on old yahoo forums, you might remember me having problems holding boost, well unfortunately i still am.

I have tested everything and all seems good, but i do suspect i have blown the inlet manifold gasket. (what else could it be) i was under the car yester day and notice that there was a little bit of oil leaking from the inlet gasket, (i have a turbo which is leaking oil,) so im pretty sure its leaking. Because i cant get anything much more than 10psi of boost, it will peak up to 14ish but then straight down to 10 or below 10

i will be ripping off the manifold soon, i just want to know is there anyway of testing that its blown to save me the trouble.

oh, im running a microtech, hence why its not runningl like shit with a leak.

cheers

angel

[tassuperkart]

Thats a tricky one.
Have a look around with a small mirror to see any signs of the oil blowing or spraying around . To cause boost dramas, itd have to be quite a hefty leak alright and there should be evidence of it somewhere.

Im almost certain youd have to be well hearing the hissing blast of air to drop boost pressure off that far.

If the car runs smoothly with no "hunting" on idle Ie one cyclinder getting more air due to a leak at the manifold head joint then the next step is to look at the manifold top and bottom half joint.
A decent leak here would present as little more than increase in idle speed.

Same goes for the throttle body gaskets. There may be a segment of them blown away.

Check that the PCV valve is closing off under boost pressure and not bleeding boost into the crankcase and same goes for the brake booster line and other assorted vacuum lines running across the manifold from side to side, particularly the ones going off to the charcoal canister and blah (if still fitted).

Change the gaskets as a matter of course and dont forget the gasket between the upper and lower halves of the manifold itself.

Ive had this exact same leaking drama with my FJ20et. Not a big leak mind you, just hissing past the very thin manifold gasket on one cylinder, but enough to actually have fuel vapour spaying out underneath and leaving telltale kinda grey "washing" marks on the head casting. I always wondered about the vague fuel smell under big boost!
This can be an issue tho as along with air comes fuel and this leads to leaning out of that cylinder as boost rises and possible detonation and/or burnt valves.

Just gotta start from scratch M8 and do things in order.

L8tr
E

[angel]

Thats a tricky one.
Have a look around with a small mirror to see any signs of the oil blowing or spraying around . To cause boost dramas, itd have to be quite a hefty leak alright and there should be evidence of it somewhere.

Im almost certain youd have to be well hearing the hissing blast of air to drop boost pressure off that far.

If the car runs smoothly with no "hunting" on idle Ie one cyclinder getting more air due to a leak at the manifold head joint then the next step is to look at the manifold top and bottom half joint.
A decent leak here would present as little more than increase in idle speed.

Same goes for the throttle body gaskets. There may be a segment of them blown away.

Check that the PCV valve is closing off under boost pressure and not bleeding boost into the crankcase and same goes for the brake booster line and other assorted vacuum lines running across the manifold from side to side, particularly the ones going off to the charcoal canister and blah (if still fitted).

Change the gaskets as a matter of course and dont forget the gasket between the upper and lower halves of the manifold itself.

Ive had this exact same leaking drama with my FJ20et. Not a big leak mind you, just hissing past the very thin manifold gasket on one cylinder, but enough to actually have fuel vapour spaying out underneath and leaving telltale kinda grey "washing" marks on the head casting. I always wondered about the vague fuel smell under big boost!
This can be an issue tho as along with air comes fuel and this leads to leaning out of that cylinder as boost rises and possible detonation and/or burnt valves.

Just gotta start from scratch M8 and do things in order.

L8tr
E

hi evan, yeh i have checked pretty much all vac lines and what not. But now that you mention it, there is a real strong fuel vapour smell after i boost the car, strong enough to make me a little light headed.
I guess that would indicate a blown gasket

[tassuperkart]

If thats the case Angel, then Id bee looking at a buggered gasket and the joint of the manifold and the head.
IMHO neway!
Good luch with it!
L8tr
E

[photoglossy]

Can you hear any whistling sounds when the pipes are starting to pressurise? (from slight vacume onwards)

I had a very loud noise about 3 weeks ago. I took a look it my compressor outlet (3 bolt type) and it was missing 2 bolts! there was a huge leak there. Altho i could still hold 14psi well... (probably screwed my turbo, i know)

Its will be very hard to tell if you have a leak eh. You could poossibly put some paper just under where you think its leaking from, go for a drive then check the paper to see if there is any oil traces...

[SammyET]

(probably screwed my turbo, i know)

How bad is it for a turbo to drive with a blown hose??

Sam

[Panda_ET]

basiacally if there is a massive leak the wastegate wont open till its presented with its preset amount of boost (eg 7psi) now if there is a big enough leak the boost being supplied to the wategate actuator will actually be substantially higher than than what the actuator is seeing so it may not open teh gate and overspin the the turbo. depends on turbo size as well say fora T2 to produce 6.5psi it takes 100,000rpm thats a shit load of rpm to pruce a small amount of boost so to produce 13psi witha T2 ur lookin at teh 200,000rpm range for shaft speed which i would say is well out of its effeciancy range and also heading well into the oversped shaft range Im ont sure on shaft speeds of the T28 etc but i know its safe to spin a GT28R upto 28psi its out of its efficiency range but it can handle it without destroying itself.


haha i bet this made no sense at all but basiacally dont run the car without piping otherwise theres nothing controlling shaft speed. a wastegate doesnt really control boost it controls shaft speed.

so if u havea massive air leak the gauge maybe reading 10psi (as an example) but the turbo is spinning fast enough for 18psi it can damge ur turbo if its not upto the task.

please people correct me if i am wrong as much info possible is nice to have

matt

[photoglossy]

Well said matt... I can never seem to explain these things without tying myself in a knot, so im glad you said it and not me

[angel]

Can you hear any whistling sounds when the pipes are starting to pressurise? (from slight vacume onwards)

I had a very loud noise about 3 weeks ago. I took a look it my compressor outlet (3 bolt type) and it was missing 2 bolts! there was a huge leak there. Altho i could still hold 14psi well... (probably screwed my turbo, i know)

Its will be very hard to tell if you have a leak eh. You could poossibly put some paper just under where you think its leaking from, go for a drive then check the paper to see if there is any oil traces...

not i can really hear any whistling noises, but ill rip the inltet manifold off when i put my new GT28r on, theni can finally run 18 psi and see the full potential of the car.


cheers

[raddavey]

To test for leaks i put a bung on the throttle body with a little nipple on it then used the compressor to check if any air comes out anywhere. Air will go through the engine unless you remove the rockers to shut all the valve but you should be able to get it up over 20psi and hear for leaks. I found a few when i did it and substantually reduced them. I could not stop the TPS from leaking through the shaft, although its only a slight leak.

[angel]

To test for leaks i put a bung on the throttle body with a little nipple on it then used the compressor to check if any air comes out anywhere. Air will go through the engine unless you remove the rockers to shut all the valve but you should be able to get it up over 20psi and hear for leaks. I found a few when i did it and substantually reduced them. I could not stop the TPS from leaking through the shaft, although its only a slight leak.

does that really work, if some valce are up, then you can pressure test it casue it would flow through, or am i wrong

[raddavey]

I tried it and it worked. The turbo has to do the same thing, provide pressure even though the engine is flowing most of it through. You will need to crank your compressor up and hold the trigger on the whole time pretty much. Remember the air will only escape through the engine if both the exhaust and intake are open at once (overlap). If you have a stock cam i dont think there is much overlap. You could position the cam at a point where this doesn't occur or just loosen the rockers off.

It'll be pretty obvious where the leaks are as you'll hear them hissing out.