Need opinions and/or thoughts on 4.0 ohv issue

[cr_the_machinist]

I have a 99 Ranger 4x4 with 96,000 miles on the clock. The last couple months it has started to burn oil and burn very small amounts of coolant. I have replaced the plugs, wires, torqued manifold gaskets and valve covers, searched for vacuum leaks... replacing one questionable line. I had new heads put on the truck a little over a year ago, so I don't think the valve stem seals would be leaking just yet (I hope not atleast). Compression tests come out to an average of 160 psi with all cylinders staying within a 10% field of variance and no major jumps in compression upon wet tests. I took off the upper intake manifold to torque the lower manifold and there is oil coating the intake passages and up into the upper intake as well. PCV is working properly. It has a slight stumble at idle like there is a vacuum leak but there is none to be found externally. I'm thinking that my lower intake manifold gasket has gone bad and is sucking oil into the intake system. All plugs show signs of quick carbon build up and #4 is soaked in unburnt oil. Does anyone have any thoughts on the situation? I'm going to schedule an appointment at the local shop to get the truck a leak down test and see if they have any way of pin pointing internal vacuum leaks.

 

[cr_the_machinist]

Been reading up on how to translate running engine vacuum reading, so I'm going to pick a vacuum gauge and see what readings I can pull from that. Hopefully that will help me sway toward a closer conclusion. I just hope that its not a head or a head gasket problem again. Thinking of replacing the rockers, rods, and lifters while I'm in there if I end up doing the lower manifold gasket.

Anyone have any thoughts at all or ever have this problem before?

 

[ven0msho]

I have a 99 Ranger 4x4 with 96,000 miles on the clock. The last couple months it has started to burn oil and burn very small amounts of coolant. I have replaced the plugs, wires, torqued manifold gaskets and valve covers, searched for vacuum leaks... replacing one questionable line. I had new heads put on the truck a little over a year ago, so I don't think the valve stem seals would be leaking just yet (I hope not atleast). Compression tests come out to an average of 160 psi with all cylinders staying within a 10% field of variance and no major jumps in compression upon wet tests. I took off the upper intake manifold to torque the lower manifold and there is oil coating the intake passages and up into the upper intake as well. PCV is working properly. It has a slight stumble at idle like there is a vacuum leak but there is none to be found externally. I'm thinking that my lower intake manifold gasket has gone bad and is sucking oil into the intake system. All plugs show signs of quick carbon build up and #4 is soaked in unburnt oil. Does anyone have any thoughts on the situation? I'm going to schedule an appointment at the local shop to get the truck a leak down test and see if they have any way of pin pointing internal vacuum leaks.

Sounds like you have more research to do on the oil issue, but you want to consider that the two can be separate issues.

Starting at about 100K my 97 4.0 Ranger started occasionally needing coolant and I was wanting to do a leak down test for a few months but never got around to it as I was fearing it was a headgasket as I could occasionally smell a whiff of coolant in the air.

Turns out that the vacuum operated valve that lets coolant flow to the heater core (when you request heat) had been slowly dripping coolant one drop at a time from the shaft that the vacuum actuator moves with. This then dripped directly on the right bank exhaust manifold which is why I never found coolant under the truck.

Don't know if 99 has a similar setup but it would be an easy check. It was a $25 part at the local autozoo and my coolant levle has been holding fine ever since.

 

[cr_the_machinist]

Yeah, it has the same setup. I'm pretty sure its not that. I'm pretty sure the valve stem seals are shot on cylinder 4 and probably others. It pukes blue smoke on start up pretty bad now. I'm going to tear down the top end of the engine myself and take a day or two off work to do so. I'm tired of paying mechanics to get a half ass job. I knew something else was going to happen since it took them two time to correctly seal the lower intake.