88 22R Carbureted: Is the donut gasket under the lid of the air cleaner housing important. Mine is totally worn out. I want to throw it away, but if that means the housing is going to leak I'll try to replace it. Thanks in advance

 

If the gasket is bad, or missing, there's a path for the dirty, dusty, nasty outside air to go directly down your carb, and into the cylinders. Real bad for rings, cylinder wall wear, valve wear, cat clogging up, you name it. There's a reason for air filters after all. If the input air path isn't sealed up tight, the air filter may as well not even be in there.

Mine, the one on my pickup, 87 22R, factory carb (still), etc, started to lift off the lid years ago. I used a little RTV, and it's stayed nicely in place ever since. No dust in the carb throat, so I got a good seal. It was pretty important to me, because at the time, I lived in Yuma, Az., and there's dust in the air constantly. Lots of dust. Very abrasive dust, that will eat an engine up fast.
Very worst, maybe you can run a bead of RTV around the inside of the lid where the gasket was, to act as the gasket. Make sure it's good and dry before you put the lid back on. Check for dust in the carb throat after a month or so. If there's dust, you didn't get it. Try again. Maybe a bigger bead, maybe a little thicker bead, something.

Good luck to ya!
Pat☺

 

There are three round gaskets in the air cleaner assembly: two gaskets sandwich and seal the air filter, and a larger, thinner gasket that is attached to the edge of the lid.

The two gaskets (same part number) around the air filter are very important for keeping dirt from going around the air filter and into your engine. The other gasket around the edge of the lid is on the "dirty air side" of the air filter, so it isn't as important as the other two for keeping out dirt, however, it keeps the metal lid and the metal air cleaner body from rubbing on each other.

All three gaskets have been discontinued from Toyota a while ago.

Some aftermarket air filters have a rubber top and bottom that might seal on its own, without the factory gaskets, but I have not tested to see if they actually seal. I use the OEM Toyota filters which have hard plastic tops and bottoms, and definitely need the factory gaskets in place.

If your gaskets are in bad shape, you might need to get creative with some universal seal. If the gaskets have just come loose, a little RTV sealant will work as 2ToyGuy mentioned.


Diagram from parts.toyota.com

 

(This is my first write-up. Any pointers you have would be helpful.)

Does air leak past the filter if you don't use a gasket?

I ran my own tests. The lid of the air cleaner housing does NOT, in fact, seal up to the filter unless you have a gasket. I have the aftermarket air filter with the neoprene (I'm assuming) rim, NO LID GASKET, and I tested the seal using WD-40 and found there is no contact between lid and filter - NONE. The original factory gasket serves as not only a seal, but a spacer, which is unfortunate. (Why does life have to be so damn complicated!)

Hypothesis:Toyota made a mistake when they discontinued the gasket kit.
Hypothesis: Toyota must have assumed the aftermarket neoprene top of the air filter would be enough to make the seal.

Results: BOTH hypotheses are false. Toyota didn't err in discontinuing the gasket kit. The neoprene top of the air filter does not seal up to the lid.

My results seem contradictory. Read on.

But first, let me show you how I tested the inner and outer seal of the air cleaner. First I sprayed a layer of WD-40 on the neoprene top of the filter. Then I ran the engine for about 1 minute. No vapor trails found within the filter circumference. Then, I sprayed WD-40 on the outside of the air cleaner around the rim and ran the engine for a minute. Only a slight amount of WD-40 got into the space between the outer surface of the housing and the filter.

Then, I blocked alternative points of air entry in an attempt to see if the air cleaner leaks air. I began by taping off the inlet openings. No change in engine operation, idle or 2k RPM.

Then, I taped around the air cleaner rim thinking that if the engine was breathing from the rim I could suffocate it. As I taped the rim, the engine hiccuped once or twice.


Taped all normal points of air entry to try to suffocate engine. Although it hiccuped once in a while when I added another piece of tape, it continued to run just fine. No vapor trails found.



Added more tape. Really tried hard to suffocate the engine to prove whether the lid seal really means anything. Still no vapor trails. Very hard to prove that air makes an end run by squeezing over top of the filter.

Then, I removed and taped all incoming hoses. This is the only way to cause a stall, and not due to suffocation, but rich mixture at idle. I mean,if you keep your foot on the gas you can still run it. Still no vapor trails found. How the engine really gets air I have no idea.


Removed and taped all incoming hoses.

During this entire process, even though there is no contact whatsoever between lid and filter, the engine didn't suck in the WD-40 on top of the air cleaner. Not a drop. I cannot prove any air leak between lid and filter.

FURTHERMORE, by spraying around the outer rim of the air cleaner, I found only scant penetration of the WD-40 landing between outer rim and filter.

Therefore, I did the logical thing and got around to making a gasket (anyway). I detest having to make my own gaskets and stuff. I'm strictly a bolt-on enthusiast, which means I buy a part and get someone else to bolt it on! But for once I did what a man's gotta do and got out the RTV. And this stuff:


Found this in the Home Depot weatherstrip bay. It's called caulk cord.

Caulk cord comes sticky out of the package, which means its easy to keep in place while you are shaping it. While unrolling it, It tears very easily, which is annoying, but you can press it back together. It's not sticky enough to make a permanent seal so you have to apply adhesive first so that it doesn't fall off during prolonged use. Also, you have to coat it with something to make it more stable so that the air cleaner can be opened for service. I used RTV.


What you are seeing on the inner ring is a thin layer of RTV, a single wide layer of caulk cord, and then a slathering of RTV on top. On the outer rim, I pressed the caulk rope thinner and used black RTV (ran out of red). Red RTV is better. The black RTV was really hard to control.

Butt ugly, wouldn't you say? More importantly, it's of dubious value. Guess Toyota figured that out before they discontinued the gasket kit.

Tips:

• Cure the RTV in a regular kitchen oven by baking at 170 degrees and allowing it to cool. Three cycles should be enough. This will allow you to safely reassemble the air cleaner and get back on the road.
• If you choose to use RTV, don't test your new gasket with WD-40 like I did. WD-40 is a solvent for RTV.
• Don't let a bozo go near your air cleaner with any kind of solvent - it could dissolve the RTV and leave you with a mess. That's what happened to my original gasket - had it RTV'd but it fell off because someone spilled on it (probably me!).

 

Using the diagram Old87yota kindly posted I'd say that the crucial seals is the 17841. Both of them. Those inner seals is what prevents anything from bypassing the filter and going straight down the throat. Just like everything else, air will take the path of least resistance, so if that seal is missing or broken air will choose that over going through the filter. The outer seal, 17845, would keep air from by-passing the hot air intake off the manifold. maybe a slight difference when cold, but once warm I'd think nothing noticeable.


I saw Summit Racing had generic material available. They tend to favor domestic vehicles when it comes to that sort of non-specific-application stuff, but maybe worth a look. Otherwise any of that adhesive backed strip foam(I'd get the dense cell one) should work. It is a bummer Toyota discontinued, but they walked away from carbs(in the USA at least) over 30 years ago.

 

Thanks for the reply. I appreciate your time. Even if I completely taped off all openings, the engine breathed fine, indicating that none of the air cleaner gaskets are critical. Furthermore, I have never had a 22R with a bottom 17841, and I can tell from the dirt trapped in the filter that air was going through the filter. So please look back at my hypothoses. Both are incorrect. It's not possible, unless you have some kind of engine laboratory, to prove what path the intake are is taking.

 

Unless there is a very large leak bypassing the air filter, there will still be air passing through the filter, so it will still get dirty, even with air leaks. There is also a gasket that goes between the air cleaner and carburetor.

All of these 22R Trucks came with all three gaskets boxed in the diagram I posted earlier from the factory. My Truck still has all three. Toyota would not have included them if they didn't think the gaskets were important.

Toyota most likely discontinued these gaskets not because they didn't think they were important, rather the demand for them was really low. My gaskets have (so far) lasted 35 years. There was probably so few people replacing them after 15 -20 years that Toyota decided that it was not worth it to keep such a low volume part in stock.

Air can also come in through the Hot Air Intake pipe on the inlet to the air cleaner.

 

I'll test blocking the hot air intake pipe

 

Toyota doesn't do unnecessary parts. I'd daresay most car companies don't want to waste money on something that serves no purpose. What was always interesting, when we asked Toyota engineers why something was done a certain way it was often for a reason we never thought of.

If you don't think the part is necessary than don't bother trying to replace it, just run your truck without it. It's your call. And if nothing of consequence ever happens you can assume either you were right, or you never experienced the conditions for which Toyota had made the seal for.

But if you want to test, take the air filter and wrap the filter material with masking tape. 3-4 wraps of 2" ought to be sufficient. Then put it back in the air cleaner housing. If your truck won't stay running you can assume you were possibly correct(I say possibly because you still don't know Toyota's intended purpose). But if it stays running. well...

 

I recently picked up an 85 with the 22R. The top (inside breather lid) gasket is stretched out. I plan to remove and clean the mating surfaces and shorten the length of the gasket and RTV it back in place so rests concentrically on the filter. If I’m not happy with it, I plan to use a piece of tailgate weather stripping in a circular fashion. For me, the tertiary method would be making a gasket with a bead of RTV. It is a bummer this gasket seal was discontinued.