jcroper

My 90 4Runner (3.0, AT, 4WD) has started issuing dark smoke, in light quantities, from somewhere within the engine compartment. It happened sporadically for several months but I always assumed it was leaked oil burning off on a hot engine. Small wisps will sometimes slowly drift into the interior, presumably through the AC/heat system (only when it's set to fresh intake, not recirc). It's been happening regularly for the last few weeks and may (very) slowly be getting worse.

I've tried to pinpoint the source and verified that it's coming from the driver's side. I cleaned what I could off the block and nearby surfaces to try to rule the leaked oil option out, but the problem was not resolved. I have a fairly consistent leak (maybe an oz. or two a day), but I usually keep on top of it, and I use Mobil 1 full synthetic 10w-40 for the truck. Recently I have slipped a bit and it was lower than usual - almost two quarts. I filled it up two days ago and hoped it would help. The amount of smoke seems to have lessened but not disappeared.

Upon further inspection it seems it may be coming out of somewhere in the air cleaner hose between the MAF and the TB. There is a small plastic box halfway between the two which the hoses connect to (sorry I don't know its name). My next plan is to remove the hoses/box to see what I can see.

While it doesn't come out in large quantities it does seem to be a grimy, dirtier smoke than leaks I've seen on other cars. The truck still seems to be idling/driving without problems.

Does anyone have experience and/or thoughts with this?

The only other recent repair was on my cooling system. Temps would get worryingly high (especially with a nice toasty summer in Louisiana), and the coolant was disappearing somewhere but regular top-offs kept it in check. Turns out there was a very small hairline crack in the radiator. Took care of the radiator and temps have been fine with no loss of coolant. There appears to be no oil in coolant and no coolant in oil.

I would appreciate any help figuring this out, as I'm quite comfortable working on the truck but certainly am not a toyota expert.

Slowey23

Check to see if it's coming from the valve cover breather

jcroper

Makes sense. I was wondering about it. I haven't had a chance to check since it's only done it once in the last several days. I don't think the leak is coming directly from there, but a bit of back flow should be reasonably possible, right?

Now for the questions that make me sound clueless: if this is where it's coming from, (1) is it causing a major problem and (2) what would the fix involve?