Smokin exhaust during down hill Compression.

[ZuperDave]

Ok gear heads,...I've been having this problem for several years and now it is starting to bother me,....When traveling down hill and using the engine compression to slow my speed I have a problem with smoking from the exhuast when I start to excelerate again. What would you say is going on inside that motor? She does burn a bit of oil, maybe about a 1/4 of a quart on every run I take from Hanford to Bald.

Ruby has a 5.0 EFI out of a 1990 Mustang backed with a C4 Automatic. Actual Miles on Motor is unkown.

 

[hlt75]

most likley worn rings, vacum is high on decelration there for sucks oil past the worn rings

 

[jurob]

my guess, valve seals.

do compression check 1st

 

[tjsaye]

valve guides worn

nothing to worry about solution, nurled bronze guides installed when you get your next valve job..

 

[76Broncofromhell]

X2

Valve guides and seals. I run positive seals on mine, but a good knurling job and umbrellas should do the trick.

 

[4rdnuts]

I think any of the gear heads in here can tell you whats goin on internally...
suck, squeeze, bang, blow... fuel spark and and oxygen delivered at the right time baby... lol, but really........


personally, i dont like compression tests unless I am looking for a major difference in compression for cylinder to cylinder, and the difference has to be significant, I know the rule of thumb is 10%, but still, I am looking for 50% or more. I immagine other guys in here feel real different about that, thats just my 2 cents. If you want to do a real test of valve seat, ring seat, jump time, do a leak down test instead.

What color smoke you getting, black = rich, blue/white = oil

 

[Pa PITT]

I'm inbetween I'd put Umbrellas seals on it and live w/ anything else except plugs fouled .....

 

[4rdnuts]

I'm inbetween I'd put Umbrellas seals on it and live w/ anything else except plugs fouled .....

i defintaly agree there

 

[ZuperDave]

I'm pretty sure the smoke is Bluegrey, but I'm waiting for confirmation from someone who followed me down this past weekend. It is not noticalbe by me, so its not real bad.......

 

[wildbill]

If it smokes going down hill then I would ck. the drain back holes in the heads and replace the PCV valve as it sounds like you are sucking oil from the valve cover and burning it. A bad PCV valve wont close tight when dirty good luck. Bill %) ;D

 

[blubuckaroo]

If it smokes going down hill then I would ck. the drain back holes in the heads and replace the PCV valve as it sounds like you are sucking oil from the valve cover and burning it. A bad PCV valve wont close tight when dirty good luck. Bill %) ;D

The PCV is just a check valve. It just keeps the the crankcase from getting too much pressure durring backfire and blowing out your seals. That's the only reason for it. If it weren't for the possiblity of backfire, a straight vacuum line fould work.

 

[ugly74]

definitely valves seals and/or guides. with a high vaccuum condition (engine braking) the cylinder will suck oil from the head around the intake valve stem.

 

[ZuperDave]

That sound about right,....Thanks for all the input.


I think I'm just going to sell it,.......Any takers?



















NOT!,......Just kidding.