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A while ago I had my valve stem seals replaced with the head on. This was done by a fairly reputable shop in my area. All was good and the slight smoke had gone away. Now a few months later down the track it appears that my car is slightly smoky again. Exact same issues. Smokes a little bit when taking off and on cold start. If it idles for a bit when warm and I tap the accelerator it will smoke. Basically it seems like the valve stem seals have gone again. I had made sure to use OEM valve stem seals instead of the aftermarket ones that leak.
I was told by the shop that the exhaust housing for my turbo was too small to funnel all the exhaust out and as a result pressure builds up and unseats the valve stem seals. When I had my valve stem seals done previously, I was told that a few of them had been "pushed up" and that was the cause of the smoke and was told to upgrade to a turbo with a larger exhaust housing. Is this a plausible answer to why my valve stem seals have unseated again? I'm a bit skeptical. Could it be a bad valve stem seal job? The same shop also said that the smoke in the first place could of been turbo seals and once again suggested I upgrade my turbo.
Compression Test showed up fine. Leakdown was a little high at around 17-22% but consistent across all cylinders. It's an old ish engine and was a track car beforehand so I'd say those numbers aren't too surprising. The turbo is boosting fine, no weird sounds or anything.
Info about the car:
Build 1.8. Not sure what's done exactly though.
Turbo: Garret GT2871R running around 19PSI. It used to run 25PSI without issues but it's been slightly detuned for now.
Manifold: NitroDann TwistMount I believe
Power: 250KW/580NM on 22PSI but has been turned down to 19PSI. Maybe 230-240KW (320~whp)
3" Exhaust. Running a single muffler in the rear. No cat and resonators.
E85 but runs on flex fuel
Some sort of catch can setup.
Do you guys think it's a bad valve stem seal job? Is the turbo exhaust housing theory given by the shop plausible? I've heard you'd require ridiculous levels of boost to achieve that but I can't find much on the internet. Could something like a improper PCV system cause this? I've noticed the large fitting going into the left side of the rocker cover and next to the throttle body is a little loose feeling and the surrounding area is a little oily. My catch can area is also oily along with a slight rocker cover gasket leak.
Let me know if I can provide any more information. I didn't do the build so I'm not the most familiar with the car. If you need better pictures, videos just ask.
I did valve stem seals a couple of times with similar results. Finally pulled the head and confirmed excessive valve guide wear was the issue.
Any ways to somewhat distinguish between valve guide wear and just bad valve stem seals? Preferably without pulling the head.
If I pull the head I might as well do a freshen up but I'd like to avoid this for as long as possible. It drives fine and doesn't burn much oil. Not enough to notice between oil changes anyway.
I'm with Spartan, very likely valve guides if non-ST seals were used. How many miles on the head?
Sorry for the late reply.
I've been told around 60,000kms/37,000miles is on the head but that figure seems extremely high for a forged motor. It was rebuild in approx 2015 from what I can see.
Smoke doesn't seem to be getting much worse. I suppose it isn't an urgent thing to address as long as I keep the oil topped up right?
Last edited by nonchalantwhale; 05-23-2022 at 01:58 AM.
Am I wrong in thinking 20% leakdown is more than a little high? We rebuild at 8-10% leakdown. A good NA race motor is 6% or less. 20% leakdown is huge.
The result from a leak down tester doesn't mean much, they can only be used as a relative measurement. I used to develop them, so I have substantial experience with the concept. There are several types, single gauge, double gauge, and fake double gauge. The basic premise is that they are comparing the internal flow rate of the tool to the leakage rate in the engine. The issue is that the orifice inside the tool is not the same from one mfg'er to another. To add insult to injury inexpensive gauges have generous tolerances.
There is an SAE/FAA standard for the orifice diameter and length, but they are difficult to manufacture so most companies fudge the dimension. The dia is supposed to be .040" X .250" long with a 60deg lead in angle. It is hard to drill a hole that small, that deep. Another issue is that for smaller engines with cylinder displacements under 500-600cc's the std orifice is too large. The calibration of the testers is another issue. If it is a tool that has a pressure and percent gauge, but is only calibrated on the right (down stream) % gauge, it is only a single gauge tool. These are the least accurate. Accuracy and repeatability are not the same so it can be use for a relative measurement from cylinder to cylinder or from new engine to a used engine as long as the same tool is used. The actual number does not mean much without standards. From what I have seen the commercially available units are fairly optimistic because the flow jet has a large volume.
I've been told around 60,000kms/37,000miles is on the head but that figure seems extremely high for a forged motor. It was rebuild in approx 2015 from what I can see.
Smoke doesn't seem to be getting much worse. I suppose it isn't an urgent thing to address as long as I keep the oil topped up right?
It all depends. My old 1.6 was smoking like a trooper . It had done 40K racing miles Miles Ive had it in for 10 years after it was taken out of a racing car . I got dobbed in with my smokey engine and got a nice letter that I have 4 weeks to fix it. Or face a massive fine.
a Head rebuild will probably be about $1200 AUD or a little more with new valves & Valve guides.... but then ... can your rings handle it?
It all depends. My old 1.6 was smoking like a trooper . It had done 40K racing miles Miles Ive had it in for 10 years after it was taken out of a racing car . I got dobbed in with my smokey engine and got a nice letter that I have 4 weeks to fix it. Or face a massive fine.
a Head rebuild will probably be about $1200 AUD or a little more with new valves & Valve guides.... but then ... can your rings handle it?
I’m considering pulling the head soon and having a look at what’s happened and giving everything a refresh.
From what I’ve gathered, everyone reckons it’s valve guides which would require the head off. While I’m there I might as well freshen up the insides right?
Any last minute things I should check before sending it in?
Does anyone have any reputable shops that won’t charge an absurd amount for this work in Sydney? I’m not too keen on going to the shop that did my seals as they’re adamant it’s the turbo and misdiagnosed it in the first place.
Hoping to keep everything under 3k aud or is that unrealistic?
04-10-2022, 12:17 AM
Valve Steam Seals Leaky again after replacement
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