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Discussion Starter · #1 · (Edited)
Hi guys, so I have a separate thread for my hesitation issues, but finally got around to doing a pressure test and thought it would make more sense to have this as a separate thread in case it may be useful for anyone else to see.

Here's a link to 2 short videos I took, showing the pressure test setup, and then my leak areas.
First off, if I'm doing something wrong, just let me know as I'm just learning this as I go along with the car.

Ok here are my questions/what I'm looking for input on;

-could this actually be the source of my hesitation/bucking?! I don't know why, but I started going down multiple other paths before finally coming back to the pressure test. Plugs and wires done, fuel filter replaced, TPS tested, injectors next on the list I think (to get cleaned/flow tested)

-The rear turbo intake pipe o-ring (not sure what it's actually called), I figure I can just match up the size from a parts store and replace easy enough. I'm planning to order a replacement BISS screw set (screw, o-ring, plug) from Ninja which I know will take a month or 2 but don't think that's a huge rush/problem? maybe I'll just find a replacement o-ring in the meantime.
Any ideas on my 3rd leak area down near the front turbo? I'll jack the car up so I can get to things better, but it might even just be the intake tube attaching to the turbo itself, though I'm not sure yet as I couldn't tell from above.

-I think I should replace some of the older looking vacuum tubes... I've considered doing the vacuum reduction, but torn on that as I really like the idea of keeping the car's stock functions though I am open to opinions on that. End of the day, I want to eliminate potential leak areas so it's either replace all tubing and/or remove what's unnecessary. For what it's worth, I plan on installing wideband for proper logging, and a Macboost solenoid with Blackstealth's LEDBC to work with my Chrome ECU in the near future.

-I've found this thread basically showing all of the sizes which is great:
and this came up as a recommended place to order hose from:
but is 4mm close enough to the 3.5mm that the previous link stated is our proper size? (I'm going to call around some local shops instead to see if anyone has similar quality hose which would be much easier). Amazon/ebay of course has stuff too though I have no idea on the quality.
I guess what I'm asking here is, where did you get your replacement vacuum hose and did you use 3.5 or 4mm?
 

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Lovbyts
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You might as well order the O ring for the rear turbo from Ninja also, it's only $6.
I just had to replace my turbo intake pipes for the same reason, my rear one was leaking. It had ripped on the bottom right where the it clamps to the turbo. Actually it's not hard to remove them and check the hoses. Just take off your intake, ypipe and the rest is easy to get to.
Clean your intake while you are at it if it's dirty but Dont spray any cleaner in the IAC, it will melt the was inside and ruin it. Also dont spray any cleaner in your MAF or you will remove the coating on the wires and get bad reading.

I did the vaccum reduction and if I had to do it again I wouldn't. Just my opinion.
 

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That rear turbo o-ring is a bitch, I've had brand new ones not want to seal. I've been half tempted to throw some rtv on mine and be done with it. As for the BISS screw, the part number is MD614948 and was the same part from all the Mitsubishis at the time, including DSMs, so you should be able to get it anywhere if you don't want to wait on Ninja's shipping delay. In regards to the vacuum hose size, I wish I could remember who made the post, but there was a recent post on about how the diameter of the hose doesn't really matter as most hoses are "dead head". Meaning no air actually flows and it's just using pressure change in the hoses to act on a diaphragm at the other end.
 

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Discussion Starter · #4 ·
You might as well order the O ring for the rear turbo from Ninja also, it's only $6.
I just had to replace my turbo intake pipes for the same reason, my rear one was leaking. It had ripped on the bottom right where the it clamps to the turbo. Actually it's not hard to remove them and check the hoses. Just take off your intake, ypipe and the rest is easy to get to.
Clean your intake while you are at it if it's dirty but Dont spray any cleaner in the IAC, it will melt the was inside and ruin it. Also dont spray any cleaner in your MAF or you will remove the coating on the wires and get bad reading.

I did the vaccum reduction and if I had to do it again I wouldn't. Just my opinion.
thanks for the reply. I actually want to order a bunch of stuff from Ninja, but some of it I really want to get on asap so have to look elsewhere (if I wait 2 months the season will be half over). The stuff that can wait I'll order from him still.
Rear turbo it's just that o-ring (at least pretty sure), the front turbo hose connection may be my other problem, I think I'll have to jack it up to get at that easier. My intake doesn't look to dirty but I'll give parts a clean carefully next time I'm in there.
Your vacuum reduction comment is the kind of input I was looking for, or opinions either way, so thanks. Was this because it caused you problems or just that you would rather have all original parts working?
 

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Discussion Starter · #5 ·
That rear turbo o-ring is a bitch, I've had brand new ones not want to seal. I've been half tempted to throw some rtv on mine and be done with it. As for the BISS screw, the part number is MD614948 and was the same part from all the Mitsubishis at the time, including DSMs, so you should be able to get it anywhere if you don't want to wait on Ninja's shipping delay. In regards to the vacuum hose size, I wish I could remember who made the post, but there was a recent post on about how the diameter of the hose doesn't really matter as most hoses are "dead head". Meaning no air actually flows and it's just using pressure change in the hoses to act on a diaphragm at the other end.
hmm ok thanks for the input! O-ring is at least easy to get to so I can fight with that one a bit if necessary. Great to know about the BISS screw set! Interesting about the hoses too... But the inner diameter must matter for tight fit over the hard lines or else a ton of clamps would be needed to prevent leaks right
 

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Lovbyts
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That rear turbo o-ring is a bitch, I've had brand new ones not want to seal. I've been half tempted to throw some rtv on mine and be done with it. As for the BISS screw, the part number is MD614948 and was the same part from all the Mitsubishis at the time, including DSMs, so you should be able to get it anywhere if you don't want to wait on Ninja's shipping delay. In regards to the vacuum hose size, I wish I could remember who made the post, but there was a recent post on about how the diameter of the hose doesn't really matter as most hoses are "dead head". Meaning no air actually flows and it's just using pressure change in the hoses to act on a diaphragm at the other end.
LOL, thats pretty much what I did. I pulled the O-ring, put a nice bead of black silicone and let it dry over night, then put the O-ring back on. No more leak.
 

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I had the same issue with the car almost stalling when when taking off from first gear, and rough idle, had a couple of vacuum leaks one at the throttle body idle adjustment screw which has an o ring that I replaced. Another leak at the vacuum lines going to the brake booster and clutch booster, and I can’t find this lines anywhere even at the dealer since they have a check valve inside them, has anyone changed this before?
 

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Lovbyts
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thanks for the reply. I actually want to order a bunch of stuff from Ninja, but some of it I really want to get on asap so have to look elsewhere (if I wait 2 months the season will be half over). The stuff that can wait I'll order from him still.
Rear turbo it's just that o-ring (at least pretty sure), the front turbo hose connection may be my other problem, I think I'll have to jack it up to get at that easier. My intake doesn't look to dirty but I'll give parts a clean carefully next time I'm in there.
Your vacuum reduction comment is the kind of input I was looking for, or opinions either way, so thanks. Was this because it caused you problems or just that you would rather have all original parts working?
It didn't make anything better, no performance gains and after a few years you start to forget what was disconnected and why. LoL

I just replaced my turbo intakes and my front one is perfect. Its a 91 TT. If it will fit yours you can have it if you pay shipping. I'm in Washington state.
 

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Lovbyts
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I had the same issue with the car almost stalling when when taking off from first gear, and rough idle, had a couple of vacuum leaks one at the throttle body idle adjustment screw which has an o ring that I replaced. Another leak at the vacuum lines going to the brake booster and clutch booster, and I can’t find this lines anywhere even at the dealer since they have a check valve inside them, has anyone changed this before?
I just changed mine. Get a new hose the same size. Use a utility knife and cut the check valve out and push it into the new hose. Its easier than you think.
 
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Discussion Starter · #11 ·
It didn't make anything better, no performance gains and after a few years you start to forget what was disconnected and why. LoL

I just replaced my turbo intakes and my front one is perfect. Its a 91 TT. If it will fit yours you can have it if you pay shipping. I'm in Washington state.
Thanks that's kind of what I was thinking, and I like the idea of keeping the car with all factory options working!
Appreciate that offer, and I will let you know once I've confirmed what is actually causing that front leak.. I'm more hoping that it's just better clamping req'd or something like that, but if the hose is ripped then I'll of course be replacing it.
 

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Discussion Starter · #12 ·
Realize I never updated this thread last year... Thought I'd add to it now in case anyone searched before doing their own pressure tests and came across this thread.
So summary of leak point I had last year (and a few this year);

-rear turbo intake pipe o-ring (easy replacement, consider adding a second to sort of jam underneath which worked well for me)
-BISS base idle set screw (just replace the small o-ring, worked great)
-front turbo piping clamps all needed to be tightened (didn't realize until I turned up the pressure on the test a little, but these were obvious and relatively easy to tighten once up on ramps/blocks

of note, I forgot to block off the tube going into the plenum yesterday so there was air coming out of the oil cap on the front valve cover... corrected this though (ie don't forget to block that tube!)
My vacuum lines were all fine/not leaking yet, though there are some definite signs of wear so I do plan on replacing these and already have some new silicone line for this purpose).

This may not help anyone, but hey if it helps one person even a little then I'm happy.

Cheers
Ryan
 
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