Removing Oil in Spark Plug Wells

After my successful recent r/r of the valve cover gasket :triumph: I have decided to go ahead and replace the plugs. I had read that the '94 4.0s came with copper plugs, which were the standard back then. In the event the PO never replaced them, they are way overdue @ 80K+ miles and for an upgrade to single platinum plugs. Only problem is that I notice that #5 and #6 plugs have some pooled oil in their wells, with #6 particularly bad. In fact, I’m amazed it hasn’t interfered with the proper firing of the plug. :grimacing:

Question is, what is the best approach to get the oil out of there before I remove the plugs? Although it IS engine oil, I don’t want to risk too much oil going into the cylinder (i.e. more than a tablespoonful) and causing that nightmare “oil wash” condition. :fearful: I know usually the standard approach to remove debris around plugs is with an air compressor, but I don’t have access to one. I have tried sticking shop paper towels down into the well with a long screwdriver, letting them soak a bit, and then pulling them up, but that doesn’t seem to be working very well. :disappointed: One idea I have had is that we have a full-service car wash here that has “DIY vacuums”. These vacuums are very powerful. I’m thinking maybe I can use one to vacuum the oil up out of the wells. :thinking:


Having done similar things without an air compressor, I used rags to soak up the oil. Much better than paper. Step two is to use the compressed air in aerosol cans often used to clean computer boards.
I have no experience sucking out hot engine oil with a vacuum, but it doesn’t sound like a good idea.:man_shrugging:

What’s wrong with oil going into the cylinder? It won’t hurt anything and will burn off quick enough.

Try looking up “oil wash”, or maybe it’s “cylinder wash” on Google (or even I think here on J-Lers). If a sizeable enough amount of oil gets poured into a cylinder the top pistol ring loses its ability to “grip” the walls of the cylinder sufficiently for it to travel inside the cylinder properly, namely in regard to thrust on the “ignition”/power stroke. Apparently that means it just glides loosely up and down the cylinder only b/c of its attachment to the crankshaft and not by responding to/being propelled by the igniting of the fuel in that cylinder. In short, it’s contributing nothing in the way of power to the overall engine HP. That’s my best layman’s explanation of the phenomena … No idea how many RPMs it takes before the excess oil is removed from the cylinder walls by the lower “scraper” rings . Bottom line is it is something you want to avoid. :frowning_face:

Well, I tried briefly to find an article online about the issue, but seems the ones I kept coming across were about “fuel wash” (also confusingly called “cylinder wash” and “oil wash”) which is just the opposite condition - resulting from unburned fuel in a cylinder washing the thin layer of oil off the cylinder walls, resulting in excess wear to the rings, walls and/or pistons. If anyone can find something on point, please post it in this thread … :slightly_smiling_face:

Hmm, I have never heard of that. What about putting oil down a cylinder during compression test? No issue there. And as soon as the cylinder ignites, that oil is burned off. I think it would take a heck of a lot of oil to do what you explain. A tiny bit around spark plugs, I wouldn’t worry about.

Cylinder wash is NOT caused by oil, its when excess petrol is induced into the cylinders. In fact the way to overcome a lack of compression is to inject oil into the bores. Pull the plugs insert new, fire up and scare the neighbours:)


Its not the oil - but the muck that gets washed in with it.

Dilute the oil with brake cleaner or similar and suck out with a syringe attached to a thin pipe; if you can’t get a thin enough pipe, the diluted oil should wick up a rag easy enough.


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Well, in these situations, I always spray carb cleaner with the little red tube attached, usually blasts out all muck around spark plug before I remove it. Whatever rolls into cylinder at that point, I never worry. It will get incinerated. I’ve been doing this on my other two cars for 12 years, and they both have excellent compression at 175,000+ miles.

Wear goggles when blasting

Yep, after reading those articles I should have realized I brain-fahted about that matter … :blush: Sorry for the misinfo … !

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That makes sense, thanks for clearing it up.
A little oil is fine, only issue is if it’s daily (like leaking valve stems), which can burn valves.

When I pull my plugs on any car, I spray them out. Oil, carb cleaner and gunk make their way into the cylinder. May run a bit rough at first, and the neighbors may complain, but within 10 seconds, all is well. :smile:

Don’t think I have heard of oil leaking down the valve stems leading to burnt valves?

And esp., hopefully, not the exhaust valves, as I have had a stem seal leak in that regard ever since I have owned Superblue. She even gives out a little puff of blue smoke on startup sometimes b/c of the issue, hence her name. :laughing: I have been assured on here that it won’t cause any damage until it is fixed, which I HOPE is correct. :crossed_fingers:

I thought if oil leaks down the exhaust valves, it can cause carbon deposits that will cause the exhaust valve not to seat properly, causing exhaust gasses to eventually burn the valve?

Regarding your valve stem seals, how much oil do you lose a month? One of my other cars, I’ve been nursing bad valve stem seals for 7 years. But I’m now losing 1 qt a month, and burning oil out the exhaust when it idles too long. Time to replace them.

The theory is that valve stem seals are only needed on the intake valves because there is a strong vacuum in the intake ports that’ll suck the oil down the stems. On the exhaust side, the pressure within the port is neutral or positive, while theoretically the PCV system is drawing a slight vacuum in the crankcase and cam boxes, so it should draw exhaust upward rather than oil downward.

I really enjoy reading your posts. I often learn new things or think about things in a new light. I knew that the valve stem seals were only on the intake side but I assumed that it was temperature related. Now I can see that it is because the vacuum on the intake ports would draw oil into the cylinders and that vacuum is not present on the exhaust side. Thank you for that insight.


Valve stem seals exist on BOTH intake and exhaust. Yes, during idle when there’s a lot of vacuum, oil can get sucked down. A good test is let the car idle for a good 10 minutes, then give it some gas. If you get a lot of blue smoke, intake valve stem seals are leaking.

On the exhaust side, when the car sits, as the oil drains back into the pan, some oil can leak down the exhaust stem seal side, where it can also puff some blue smoke at start up.


  1. While Xmas shopping, at ACE hardware, I noted a Small Craftsan compressor on sale hundred bucks. Tempted, yes. Unfounded, I have a "big’ 6HP upright and a smaller “portable”. Each very useful. I got the latter free as not working, along with some other neglected machines. The compressor after cleaning fired right up. The other 2 cycle stuff, junk… Perished in the rain it seems.

  2. I see no harm in a small amount of oil entering a cylinder.

  3. Leaking intake valve stems plaqued late 30’s Chevrolet in line 6’s. Some on fire up. .Most ignored it and no harm resulted Others fussed, GM provided a metal cap t og over the top of the valve spring and shielded the stem from most of the oil.

  4. The well worn 289 in our red 71 Mustang smoked a lot on fire up. Then cleared and ran well. Not only valve leaking oil but oil control rings as well


According to page 1E03 of my Jaguar XJ-S Parts Catalogue there are 12 “Inlet Valve Seals” ( Part Number EAC5032) on the 5.3L V12 engine and none mentioned for the exhaust valves.

The EAC5032 Inlet Valve Seals are also used on the 4.2L XK engines, which I am much more familiar with, but again the seals are on the six Intake Valves and not on the six Exhaust Valves.