Smoke test results... I got leaks!

[JoshT]

If you've seen my post in the General Discussions section, you'd know I just received a Smoke Machine for leak checking my V8 swap's intake system. Well I've definitely got a few.

EDIT: This swap is 2000 Explorer 5.0L based, so using all of the parts from that.

So far we have:

• EGR
• IACV
• Throttle Shaft
• Intake duct
• #3 injector
• Dipstick Tube
• Oil Cap

Lets work down that list...

EGR: It would appear that the smoke is coming out from the hat portion of the EGR valve. If smoke can get out air can get it. I don't know if this is something that would change with vacuum applied, if this is a designed in leak (IE: crank case vent), or if it's something cause by the pressure of the smoke machine. Going to be a PITA to replace because the header to EGR pipe ain't quite right.

IACV: The IACV has a small vent cap on the top. Smoke is coming out of that vent cap. Like with the EGR, I have no idea if or how much it matters.

Throttle Shaft: Definitely should not be leaking. This is a ported unit that I got with my ported intake. I'll have to see if it is possible to repair, or if I'm looking for a replacement. Do not blame porter, no real way to test that off the engine or without something like the smoke test. I have contact out to a local company that restores carburetors, one of their services is throttle shaft repairs, but don't know if they'll touch a throttle body. If not I may be trying to locate and adapte a larger aftermarket unit since my intake is ported to 75mm vs the stock 65mm throttlebody.

Intake Duct: It appears to be split or cracked at the throttle body end where the clamp sits. I'll be on the hunt for a replacement, but may see if I can patch with silicon/RTV in the interim. Push come to shove I'll replace with aftermarket and go to a cone filter.

#3 Injector: That one was a surprise, the injector got new o-rings during the swap so it must have gotten cut when removing and reinstalling for the rebuild. Small leak, but a leak none the less. Was already in the plans to upgrade injectors when I get a tune, so I'll postpone fixing that one until then.

Dipstick tube: Was surprised at how quick the smoke machine filled up the engine and crankcase. Turns out that there must be some pin holes where the mounting tab is welded to the dipstick tube. Hardly enough to worry about, but I may see if I can seal them up without removing the tube.

Oil cap: Decent trail of smoke coming out around the oil cap. Air going into the crank case and through the PCV suystem should be coming from the intake tube to be metered. If it's sucking in air around the oil cap that would be a source of unmetered air. Might be an acceptable amount of leakage, but seems worthwhile to pick up a new cap and see if it can be fixed.

Thus far there have been no leaks in the actual vacuum lines, doesn't mean that they won't appear once the others are take care of. I was also surprised by the smoke going into the crank case. I expected it to travel through the breather tube into it, but it still filled after I removed and capped the breather. I'm wondering it if could be flowing back through the PCV valve. I'll try capping that off on the next test. If it's not going through PCV, I'm concerned that it may be a lower intake leak.

 

[franklin2]

Some EGR valves are designed to leak. Depends on what model it came from. Take the EGR valve itself off and look around the bottom edge where the openings are. If there is a little piece of felt around the edge, it's designed to leak.

It's the way they regulated the amount of EGR in the older systems. There is a metal plate inside the EGR that is acted on by the exhaust backpressure. Very little back pressure lets most of the vacuum applied to the EGR to leak past, that is what the felt filter is for. As the rpm increases, the backpressure increases, and the EGR leaks less and is actuated more, since the engine can take more EGR if the rpms are higher.

That is why the older EGR's cannot be tested with a vacuum pump on the bench. It's also why the exhaust system from the cat forward is considered part of the emissions system. It's what creates the backpressure to make the EGR work.

Sorry for the rambling above. I see something about fuel injector in your first post. I don't believe those are designed to leak, only the older type on the carb engines.

 

[JoshT]

EGR is from 2000 Explorer.

I see something about fuel injector in your first post. I don't believe those are designed to leak, only the older type on the carb engines.

Smoke leaking around the lower injector o-ring. I know that isn't designed to, figuring that the o-ring probably got cut on the way in. A new set of injectors is already on my list for tuning prep, so that one will wait until then.

 

[bobbywalter]

without actually seeing it...its subjective.

sounds typical and normal....

i have two slight leaks at the injectors that take a bit to suck water through. it has two other small leaks...especially the efi tech throttle body....enough it zeros iac....and just barely bounces. but idle is steady at 800 so...its ok with a stickshift car.

throttle shafts do usually leak....especially with old units or aftermarket units.


the leaks i have would affect learn modes but they are locked out so it sticks to the program... i just left it as changing cam and intake is happening pretty soon.

i would put a stock throttle body on and compare.

 

[JoshT]

So more info.

EGR Valve: Smoke is leaking out the holes circled in the image below. I've read conflicting opinions as to whether it should or should not leak during a smoke test. Next test I'll pull the vacuum line off the top and see if smoke come out the port, if it does definitely a bad diaphragm.

IAC Valve: Leaking from the vent cap circled. Seems that this is normal, nothing to be concerned about.

Throttle Shaft: Carburetor shop wouldn't play ball, was like they completely didn't understand what I was trying to ask about. Undeterred, I pulled and disassembled the throttle body this afternoon, to see if the shaft bore was worn or if there is a seal that could go bad. Turns out that there are o-rings sealing the shaft. I replaced them, but more on that after I determine that it fixed a leak. Got a few other things to address before then.


Intake Duct: It's chewed up in the clamp area, especially under where the adjuster is at. My guess, it was overtightened too many times over the years and took it's toll on the material. I thought I found a duct at the salvage yard today, but after I got home I realized that it is for an earlier model with a ACT sensor in the duct. Mine is a later model with the ACT built into the MAF. I could probably use the earlier duct and plug the hole, but I'm going to try to patch up my old one with some Ultra Black RTV. If that doesn;t work out, I'll source another or maybe go the DIY CAI route.

I'll scrub it down really well tomorrow and let it dry overnight before applying the RTV. Then I'll let it cure for a few days before trying the smoke test again this weekend. Probably put another piece of rubber between the clamp and that area as well to help protect it.

 

[bobbywalter]

these situations i try not to ever put rtv anywhere along intake ducting and very uneasy around even the lower intake and use certain gaskets to avoid it depending on engine.

seen too many valve and ring issues for from it coming off....and knew it because it was fouling a plug too.

there are tapes that can help....or get chewed up too if they get loose....but till you get some fresher stuff may be less of an issue potential.

the throttle body is hard to say

 

[JoshT]

I hear you Bobby. If that duct were a gasket I'd install a new one. Unfortunately it isn't, it isn't available new, and it isn't available used from any local sources. The only one I found used online is about $100. That's about $80 more than I want to spend since I could get for less than 20 if the local P-N-P had it.

There are tapes that could help, self sealing silicon F4 tape for example. I've actually got access to plenty of it. Unfortunately due to the contours and location, there's no good way to apply it. Might be a good option for an extra layer of protection under the clamp after the patch job.

The way I plan to patch it I don't think there will be any issues. Basically using just enough to "glue" it back together, no excess inside, and at most a skim kit over the chewed up area on the outside. It will be allowed to fully cure before installation. Then use something like a piece of inner tube or that F4 tape under the clamp adjuster for extra protection.

Ultra Black RTV is the first thing that came to mind, also thinking about something like GOOP or E6000 instead.

The majority of the area where silicon will be applied is going to be on the flange of the throttle body once installed. I don't think there will be much risk of what ever I use getting into the intake and inside of the engine.

 

[JoshT]

Not much to be said about the throttle body. It was leaking around the shaft, behind the spring. May have been leaking in the TPS side too, but didn't show with the sensor installed. The shaft has 2 o-rings sealing it to the body. I replaced the two o-rings. Either the leak is gone or it isn't, I'll find out this weekend.

I spent a lot of the last 20 years working aircraft fuel systems. I know an old, bad, o-ring when I see one. They probably would have sealed as long as the weren't disturbed, but my throttle body was "ported" with the upper intake and the shaft was half-shafted. To do that they had to remove the shaft.

When they ported the throat they left a sharp edge on on the bore for the throttle shaft. Even if the seals had been good, it was sharp enough that it would have destroyed the o-rings when they reinstalled the shaft. Did it to me twice before I caught the problem, thought the o-rings was just too large the first time. Hit the edges with a deburring bit and it went together without another problem.

 

[corerftech]

JoshT, sent a PM regarding a replacement part for you. My 2001 shed all of its efi goodies and is now as God intended, carbonated!
Might help. also interested in this smoke machine your using.