OT Ford ranger fouled plug

Frank (N.Mi.) · Jun 19, 2016

Wonder if any of you have seen this before...I own a 2000 ford ranger with 4 liter v6 pushrod engine. A year ago I put new heads on it to cure a cracked head on no. 4 cyl. Since then it has used some oil. I did not drive it all that much so I just kept the oil topped up til I got around to investigating it more closely. I recently pulled the plugs and discovered no. 6 was badly oil fouled. Only that one. The heads I put on were new and came with the valves in them. Is it possible oil is getting past a defective seal or badly dressed seat? If I can find my old compression tester can I pinpoint the cause? (rings, valves, etc). Hoping to diagnose this quickly...Summer is a busy time for me...Thks Frank

johnlobb · Jun 19, 2016

I also have a 2000 Ford Ranger with the 4.0 V6, and experienced the same head cracking problem you describe. My son found a place in West Virginia on the internet that had brand new heads from Australia complete with valves, and all, just bolt them on. I had to buy new head bolts and a gasket set, and it all came to under $300 in about 2009. We've put over 100K miles on it since and it still runs great. Supposedly these Australian heads were reinforced where the other ones cracked internally. So far, so good. Good luck.

RWT · Jun 19, 2016

You can usually do the valves on an older motor without problems.

I've found it rare but if you seal the valves up on a marginal motor they will use oil.

I used to run a shop and one guy walked with his Ford inline 6 head and wanted the valves done. It still didn't run when he put it back on because he had put diesel fuel in it. It started using oil bad and he pulled for nothing. It seems like I seen another case but I can't remember.

On a Ford car with a 3.8 #6 was fouling also. The hook in the spark plug ground lug would hold the oil till it cooked. I think a new plug would go 2 weeks and a cleaned plug about a week. I tried cutting the lower part of the plug ground lug off and bending the side part in until it was about the same gap as before. This let the oil drip out. It ran about a month without fouling before they quit driving the car so I don't know the long term outcome for that.

In any case I do believe the fresh valves triggered this.

RT (my 2?)

Mike M · Jun 19, 2016

When you had the head off were any of the tops of the pistons clean of carbon ? Maybe just on one edge ? If so that is a sure sign of where oil is coming up past the piston rings.

David G · Jun 19, 2016

I agree with Mike M on how to diagnose the issue, you could probably pick up a borescope from eBay and look without pulling the head.

RBoots · Jun 19, 2016

My aunt drove my grandpa's Chevy pickup with a 350 one day and it blew a head gasket and put coolant in one of the rear cylinders. It had 180,000 miles on it, so it wasn't new, but used very little oil. I put new head gaskets on it, but was afraid it had ruined the rings from her driving it home with the coolant in the cylinder. My grandpa was adamant that I put new valve seals on it, and I told him I didn't think it was a good idea, but did it anyway. After I got it running it smoked like a freight train constantly after that, and would foul out the plug on the cylinder that the head gasket blew into. I'm convinced the coolant washed the oil off the cylinders and took the rings out of that cylinder, even though it wasn't scored.

David G · Jun 19, 2016

The rings need spring in them to keep tight, you take the temper out of them when they get too hot, so they do not form a good contact on cylinders.

gab · Jun 19, 2016

Valve seals will fool you. I bought a like new 90 GMC 1/2 ton, old guy from Texas traded it in where I worked. It had 140,000 highway miles on it and a glove box full of maintenance items done in most of the states in the country. Shortly after I bought it, it went through 3 qts. of oil in less than 1500 miles. One of the glove box receipts was for valve seals so I started checking them. Every one was damaged by improper installation. Truck never used another qt. of oil between changes and I sold it with 286,000 on it.

Steve@Advance · Jun 19, 2016

I would replace the plug, get it running right. Be sure that cylinder is firing, not misfiring from a bad plug wire, or vacuum leak.

Drive it a few miles to get the exhaust cleaned up and up to temperature. Watch for smoke. Might even get someone to follow you. If it smokes on acceleration, it's rings. If it smokes on deceleration, it's valve guides.

Frank (N.Mi.) · Jun 19, 2016

Thanks for the ideas. The borescope suggestion is a good one. I actually have one and never occurred to me! I'll be checking to see if it is small enough to go in a plug hole or pcv grommet....

jimg.allentown · Jun 21, 2016

A possibility that has not been mentioned yet....
Intake manifold gasket. This engine was descended from the older 2.9 Ranger engine. Those engines had a tendency to "suck in" the intake manifold gaskets into the valley under the manifold. At first, there were few if any symptoms, oil consumption would then increase, and finally they would start running poorly.
IF you did not follow procedure TO THE LETTER when you installed the manifold after you replaced the heads, there is a possibility of a problem there.
Bear in mind that this engine uses cast iron heads and aluminum intake manifold and plenum. Torque, sequence, and procedure are important. Valve seals are another possibility, but I would say that rings are highly unlikely from my experience with this engine.

OT Ford ranger fouled plug

Frank (N.Mi.)

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johnlobb

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RWT

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Mike M

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David G

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RBoots

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David G

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gab

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Steve@Advance

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Frank (N.Mi.)

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jimg.allentown

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