Blue smoke on hot start. Valve stem seal set for '85 2.5? Exhaust/intake different? (Page 1/2)
cebix DEC 08, 05:44 PM
Okay, I have what I think is a valve stem seal problem with my '85 2.5 automatic. Engine is newly rebuilt and has done about 1000 miles. Since before the rebuild as well as now I have a blue smoke on startup problem - much worse when started hot - it will basically smoke for a minute or two after a hot start and stumble and even die sometimes at low throttle. No smoking when driving. Though when idling for a longer time I think I can see some smoke for a second when driving off.

So I think the shop didn't do those (receipt claims they did) or didn't do them properly. Is there a trick to those stem seals? I see different types sold with different sizes and if somebody could point out to me the correct ones I would be thankful. They are cheap and from what I see it's an easy job - just need to take the valve cover off?

Or could the problem lay elsewhere? When searching through the forum I found that somebody reasoned the blue smoke at hot start was an ICM problem. Is that even possible? The engine was (still is being?) broken in with full synthetic 5W30 GM oil. I read a lot of different opinions on this but I just can't buy this type of mineral oil anywhere here and I guess my symptoms don't really point to piston ring sealing?

Thanks.
Patrick DEC 08, 05:56 PM

quote
Originally posted by cebix:

I have what I think is a valve stem seal problem... They are cheap and from what I see it's an easy job - just need to take the valve cover off?



Ummm... it's a bit more involved that that.

cebix DEC 09, 08:43 AM
Well that's not too good. Could it be the valve stem seals have gone bad if overheated? Thinking if it's related to my cooling issues and I have in fact overheated.

And what about the parts themselves? There are little rubber orings and "big" seals available, how many of those goes where? The manual isn't too helpful in that regard.
Gall757 DEC 09, 10:28 AM
This thread is for the V6, but I think the process is the same for the Duke.

Changing valve stem seals with pics.

[This message has been edited by Gall757 (edited 12-09-2019).]

cebix DEC 09, 01:36 PM
Thanks. So from that write-up I guess I need 8 oring seals for both exhaust and intake stems and just 4 cup seals for the intake ones?

There are different sizes from what I can see... My valves are original, the shop said they were good so I didn't order them for the rebuild. Guess I should take the valve cover off first and measure the stems?

EDIT: Also there are different materials available, silicone, viton. Which one is better?

[This message has been edited by cebix (edited 12-09-2019).]

olejoedad DEC 09, 03:07 PM
Valve guide seals usually only smoke on cold startup.
cebix DEC 09, 03:15 PM
So what are possible causes for hot start smoking?
Gall757 DEC 09, 03:16 PM

quote
Originally posted by olejoedad:

Valve guide seals usually only smoke on cold startup.




I read a thread years ago where somebody put the oil rings upside-down on the pistons. (I hate to even mention this...)
cebix DEC 09, 04:22 PM
That's a pretty long shot I guess. I had this exact same problem before the rebuild so I don't know what that says. And it hasn't been always like that, only a few months before the teardown if I remember correctly.
olejoedad DEC 09, 06:35 PM
When the car starts and smokes, does the smoke hang low or rise up?