Lower Intake Plenum cleaning... How to?

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S.CarolinaFZJ80

S.CarolinaFZJ80

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Well guys, I would like your opinions on cleaning the lower intake plenum.

Mine is really, really nasty! Probably one mm or two of gritty gunk.

Several months ago, I pulled the throttle body and upper intake for cleaning but I decided on not pulling the lower intake due to the wiring harness being threaded through it and the tight tolerances on the bottom bolt on cylinder #6 (worried I can't get a torque wrench in there to properly torque it on reinstall).

I currently have my upper intake plenum off, again, since I pulled the fuel injectors for cleaning & fuel filter replacement prior to installing a supercharger.

I am wondering what your thoughts are on cleaning the lower intake. Can I clean it, scrub it and shop vac out the contents or should I remove it for soaking.

If the general consensus is to remove it, how hard is it to unplug the lower wiring harness and thread it back through the intake to facilitate removal? Since it appears that removing the upper harness involves way more work since it goes right into the firewall.

*Note my harness is not brittle and is in good shape.

Thanks!:cheers:
 
I would think you would be wise to pull it and get it steam cleaned and perhaps even bead blasted, especially if you are installing a SC. This will provide a really solid intake system. I believe Landtank did something similar recently while rebuilding a 1FZ for his turbo build.
 
Pulling the wiring harness is not hard, just time consuming. I pulled the lower part of the manifold when I did my head gasket and had it bead basted and pressure washed because it was looking nasty. Some of the connectors are a bit of a pain to get to/undo, but with patience and some needle nose pliers you'll be good. Also pulled the starter as it will make getting to two of the connectors easier to get at and makes installing the upper manifold much, much easier.

Installing it is much easier than taking it out. All the connectors are different so you can't put the wrong connector on the wrong sensor. It looks intimidating but really isn't bad at all. Good luck.
 
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If you're installing a supercharger & there is that much carbon in the intake you should inspect the cylinder & piston tops to see how much carbon is built up in the combustion chamber. In particular do a compression test to verify that compression values are within the acceptable range and not higher than expected.

Carbon build up inside the combustion chamber leads to increased compression which will be exacerbated by the supercharger and could lead to pre-detonation, increased cylinder temps and ultimately a failed head gasket and/or piston.
 
Thanks guys.

I got the starter out and un-plugged the two big connectors under the plenum. I still have to work my way back over the transmission and back to the O2 sensors tomorrow and unplug a few little plugs in the engine compartment.... Why they didn't just install a plug to make a sub harness back to the trany and O2 sensors, I don't know.

As far as compression and general engine health, I had the pistons steamed cleaned via a head gasket failure to the PO about 14,000 miles ago. Then I had the head replaced due to a crack that formed due to the heat from the HG failure causing it to twist. Apparently, it wasnpr't decked properly by the PO's mechanic.

My mechanic, also an 80 owner (&40) went through it while replacing the head & gave it a thumbs up. Clean and good compression he said.

I am going to have the lower hot tanked tomorrow along with the upper intake & maybe the throttle body.
 
That seems like an awful lot of work for this project. If you tie some rope to the end of the harness that is thick enough for you to push it where you want to go it will be a lot easier that lowering the cross member. Not necessary to do the job as I didn't do that but might make things easier.
 
Actually thinking about this, lowering the cross member might not be so bad. Landtank, could you please post a procedure list for doing this so anyone who comes across this thread can decide for themselves if they want to do this or not?
 
Plan for alot of time to do this job and be very carefuly with your wiring harness and connectors. Mine were luckily not very brittle but I have read horror stories on Mud of brittle harness and connectors, so be careful.

A lift would be ideal for this but in my case that was not available. Thanks to Rick's recomendation, a pair of jack stands and a jack would be handy with lowering the cross member to gain access to the plugs and the routing above the trannsmission.

Also, draw a sketch of the wire harness routing before removing it. This will ensure that you can put it back the way it came out.

A good cleaning of the upper and lower intake plentums shold run about $50 at a shop with a "hot tank". Which is a bargain, I spent half that on brake cleaner, brushes and rags plus spent about 4 hours scrubbing that the upper intake and throttle body last fall.

I will get around to pulling the rest out tomorrow and will post up pics and a how to.
 
Pin_Head said:
Leave it. Unless you fix the causes, it will come right back and it really isn't hurting anything other than looking bad. Resist the urge to be obsessive.
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It's too late to leave it as half the intake is off as well as the harness. The crud won't come back when I install the oil catch cans between the PCV and upper intake & between the valve cover breather and the throttlebody. The crud in the TB & intakes is a mix of oil, moisture and carbon from the PCV and EGR systems that normally accumulates in there as a result of Mr. T's design flaw.

I'm not being obsessive just cleaning out 195k miles worth of accumulated internal crud so my truck will run better with a supercharger installed. It doesn't look bad as its on the inside. My engine doesn't leak (anymore).

Plus I am already in there and really don't want to tear it all apart again to mess with cleaning stuff out later. I might as well do it now.
 
You're dreaming. It is not a design flaw. Virtually all high mileage engines have intakes that look like that and it doesn't mean anything. Removing it won't make it run better. Installing a supercharger on a high mileage engine is risky. Rebuilding it would be a good idea.
 
Pin_Head said:
You're dreaming. It is not a design flaw. Virtually all high mileage engines have intakes that look like that and it doesn't mean anything. Removing it won't make it run better. Installing a supercharger on a high mileage engine is risky. Rebuilding it would be a good idea.
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I started this thread to solicit valuable information from others who have done this in the past and to provide information for people who read this in the future.
Others have provided positive information here to aid in this & there are plenty of threads discussing the PCV, oil & carbon build ups but none that I saw that specifically addressed the lower intake.

Maybe I misspoke when I said it was a design flaw. The PCV system is designed to pressurize the crankcase. The oily build-up is a negative side affect of properly operating system.

Having intakes that "look like that" does mean something though. It means that the PCVs are putting a lot of oil/water vapor into the engine. Combine that with the carbon from the EGR system and you have a lot that is and could go wrong.

By cleaning out the residual oily residue that has been deposited over the last 14 years, it will absolutely improve performance from its current condition. First, the volume of air that the intake tubes can flow is decreased with all of that oily, gritty residue on the inner circumference. The texture is rough thus disturbing smooth airflow and on top of it all you have oily vapor going into the combustion chamber inhibiting combustion ever so slightly versus clean air.

Removing the oily residue from the system and eliminating its further introduction to the system by using air/oil seperators aka "catch cans" will definitely result in a better operating engine by keeping everything "downstream" oil free. The best I can hope for is better performance of the induction system. I'm not dreaming or hoping for miracles.

As far as being risky, risk can be minimized prior to adding a SC by doing all of the preventative maintenance and ensuring that there's good compression, which there is. The bottom half of the engine looked good and clean when it was apart for headwork. In addition to a new fuel filter, fuel regulator and new plugs the head was rebuilt recently along with a new head gasket. All other oil leaks have been repaired and the cooling system was recently flushed and a new thermostat was added. A rebuilt blue hub fan clutch will also be installed and a new OEM brass 3 core radiator was added about two years.

I have addressed a lot of the potential problem areas that could be a risk to a premature failure of any component(s) and can only hope for the best.
 
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PCV & EGR systems aren't design flaws - more like flawed designs. Both are there to ensure a more complete burn of exhaust gases. Nothing prevented the manufacturers from designing better/cleaner systems at the time. However during the course of the warranty, these deposits wouldn't have been an issue.

As pin_head says, all high mileage engines are going to have the same residue. I believe most of it is from oil being blown into the intake via the PCV valve - and then baking onto the intake. Turning into crumbly black stuff. My older cars which did not have EGR systems exhibited the same stuff.

You've done what you can to ensure a good running engine. No reason to rebuild the engine now. You may as well install the supercharger now - if the engine does go bad - then you can rebuild it. :)
 
I still say that the harness going through the plenum is a design flaw. I would love to punch the engineer that made that decision in the face. They did the same thing on the 7MGE, jerks! lol.
 
jlg32281 said:
I still say that the harness going through the plenum is a design flaw. I would love to punch the engineer that made that decision in the face. They did the same thing on the 7MGE, jerks! lol.
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Yeah, routing the wire harness through the lower intake definetly was not the smartest move for us having to do maintenance with our 80's but I guess that it made sense to Toyota at the time with the assembly line process for on reason or another. :confused:

When I pull my harness out I can look and see how feasible it would be to adjust the hard plastic and tape around the wires so that it comes up just aft of the intake plenum instead of through it.
 
tirewater said:
PCV & EGR systems aren't design flaws - more like flawed designs. Both are there to ensure a more complete burn of exhaust gases. Nothing prevented the manufacturers from designing better/cleaner systems at the time. However during the course of the warranty, these deposits wouldn't have been an issue.

As pin_head says, all high mileage engines are going to have the same residue. I believe most of it is from oil being blown into the intake via the PCV valve - and then baking onto the intake. Turning into crumbly black stuff. My older cars which did not have EGR systems exhibited the same stuff.

You've done what you can to ensure a good running engine. No reason to rebuild the engine now. You may as well install the supercharger now - if the engine does go bad - then you can rebuild it. :)
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Yeah, I understand that high mileage engines have buildup in them. I have had similar buildup in other engines in cars and trucks that I have owned but they have all been on PCV equipped cars and never had the severity of this build up with the EGR. The rate that it all accumulates in there is ridiculous though. I cleaned out the upper intake and TB 4k miles ago and some of the smaller ports and ducting are already getting clogged up again. That may be due to my lack of completely cleaning it by putting it in a chemical bath. I just used brake cleaner, wire brushes and a reamer for the vacuum ports.:meh:
 
Did you verify that the PCV valve was working correctly? If you suspect it's your EGR system you can take a look at the EGR valve & pipe to see they have the same amount of deposits.
 
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