CRX burns oil after stopping at the bottom of a long steep hill


#1

My 1988 Honda CRX burns oil after I drive “down” a particular hill that is about a 6 percent grade and that is about 5 miles long. There is a stoplight at the bottom of that long hill and my car always emits a big cloud of white smoke that smells like burned oil when I take off from that stoplight. I never get a cloud of smoke anywhere else; not when taking off on level ground, or when taking off going uphill, or even when taking off after driving down a “short” steep hill that is only maybe a half mile long. But whenever I drive down this one long steep grade and then stop at the bottom, I always get a huge cloud of smoke when I take off again. But the next stoplight after that is about 1 mile away with fairly level ground in between, and there’s no smoke at all when I take off at that light.

My car passed emissions testing 3 months ago. I do have to add oil between changes, but the engine has almost 235,000 miles on it.

Does anyone have a guess what I should do other than stop driving downhill?

Thanks,


#2

Change your valve stem seals.
And, if your intake manifold is designed such that it also contains coolant passages as some are, change that too.

What’s happening is that by using the engine’s compression to hold the car back going down the hill (a good habit), you’re creating high vacuum levels in the cylinders. The pistons are trying to draw air/fuel in while the air passage is largely blocked by the almost closed throttle plate. That can draw oil past worn valve stem seals, and can draw in other fluids like coolant if the engine design creates the opportunity.

If you’re not losing any coolant, just change the valve stem seals.


#3

In my experience a cloud of blue smoke after descending a hill then accelerating has been due to worn rings.

A cloud of blue smoke when starting an engine after it has been sitting for a while has been due to bad valve stem seals. Y block Fords of the late 50s and early 60s were famous for this.


#4

+1 on worn rings.
Engine braking and high intake vacuum sucks oil up past the rings into the chambers.


#5

Do you add oil between changes ? How much ?? You might not see the smoke in your mirror while driving, but ask someone to follow you and observe your tailpipe…You may be smoking more than you realize…


#6

+1 on worn valve guides for exactly the reason @Circuitsmith listed. High vacuum pulls oil past the valve seals as TSM. With this many miles, could be both.

It is time for a leakdown check! Remove the oil cap and listen for the hiss in the crankcase. Hiss, yes, time for rings. No hiss, valve seals are more likely. Compression check can show this, too. Test dry, test with a teaspoon of oil added to the cylinder. If the reading jumps up about 20 psi, time for a ring job.


#7

I would expect a hiss on a good engine when the oil cap is removed unless the PCV valve is clogged or located in the oil pan. Not sure that is a good test.

BTW, I would check the PCV valve first. A good PCV valve should create a partial vacuum in the oil pan to lessen the amount of oil sucked past the oil control rings. But at 235k miles, the rings are probably worn, but if you are not burning enough oil to be a problem, I’d just drive it.


#8

Worn valve guides are the most likely cause. On a severely worn engine, bad rings may also come into play.

Do the valve guides first, but also do a compression check.