Identifying Different Hoses (and related questions)

Hi all! I'm restoring a 1999 2.4l Tacoma, and I have some questions related to hoses. I received a p0402 (excessive EGR flow) error, and while I haven't identified the exact cause, I am definitely going to replace all hoses since they are old and cracked. That being said, there are a bunch of hoses that I haven't been able to identify, and I'm not sure if I can replace them using vacuum hose.

Here is an image of the hood, I've marked the hoses that I need help identifying. I was able to make sense of the vacuum hose diagram on the hood, and I feel good about replacing all of those. Just not sure if I can use the same vacuum hose I ordered on the other ones.

Some other general questions...

1. Any tips on the EGR valve excessive flow issue? Watched a bunch of YT vids and have some good areas to investigate, curious if there are any super obvious places I should look.

2. Any tips on cleaning under the hood? Not sure if spraying the engine components and other stuff with soap and water would be harmful.

Thanks for the help!

 

https://parts.toyota.com/a/Toyota_1..._51507_6732948/VACUUM-PIPING/675460-1708.html

Yes some of them you can use regular vacuum hose hose. The crank case breather hose and PCV hose need to be OEM hoses because of the formed shapes.

 

I don’t clean anything in the engine bay unless I have to work on it. And then, I only clean what’s necessary.

Your truck is 23 years old.
The seal packs for the electrical connectors are probably aged and aren’t fitting as tight.

I wouldn’t risk getting any degreasers or cleaners down in the connectors. Some of the cleaners are harsh. You’ll grow green crusties pretty quick if you don’t get it off copper terminals.

 

Everything is definitely falling apart, but fortunately I've already completed the higher priority mechanical repairs so the truck runs great. Lots of parts are dirty and the engine leaked a bunch of oil previously which is still on the lower parts of the engine case.

Focusing on electrical connectors and hoses at the moment, although I will need to dig into the EGR valve a bit more deeply. This guy on YT took off his intake manifold to clean and get at some of the EGR valve parts...tempted to do this myself.

 

This annotated image was extremely helpful, thank you! I will look into getting the crank case breather hose and PCV hose, and I'll use whatever leftover 3mm and 4mm hoses for the other ones you pointed out. Will prob need something bigger than 3 + 4mm for the EVAP emissions vent.

Based on what you said though, I'm curious if I need a custom hose for part #23826. I replaced everything in the attached diagram with universal hose, and the originals seem to be shaped a certain way which makes me think I might need a custom part.

I also attached an image of my engine bay that shows the hoses I replaced that I'm not sure if I need something custom. I'm also curious about the hose I outlined in purple, forgot to ask about that one in an earlier pic.

 

I did my 96 2.7L back in the fall. Sprayed if off at the car wash, used degreaser etc. Have done several older vehicles the same way but all were well warmed up and then driven a few miles back home. Ordered the shop kit from siliconeintakes.com. Most of the sizes worked and I had plenty left over. Regular rubber is fine as long as it seals, in my opinion. Then used Mothers back to black on everything else in there, plastic & rubber. Also check that PCV valve grommet. That was one of the last things I checked and found it wasn't sealing well, could hear it at RPM. Was hard (26 years old) and had to carefully chip/break it out with small needle nose pliers. Most of this info gleaned here from other's posts after some searches. Just put some spiker engineering hood struts on last month. Those are awesome too, just like others here said. Good luck with your truck.



The hose circled in your pic in purple is the brake booster hose.

 

You dont need special hoses any except for the pcv vent hose....that one needs to be fuel resistant....

 

P0402 instructions attached

 

Thanks again everyone for your new replies! My knowledge of these different hoses as grown a ton, and I feel much more confident making the necessary moves. Here is an update showing the hoses I've swapped out so far, I've been using 3mm, 4mm, and 8mm hose. Need to buy some more 8mm so I can swap out the EVAP emissions vent hose.

I'll check out the instructions regarding the p0402 error, but I've also seen some potential sources for the problem being the EGR vacuum modulator and/or the vacuum switch under the intake manifold. Those replacement parts were cheap on Amazon, so I'm going to see if one of those fix the problem. There are a couple of other hoses related to the EGR valve that go behind the intake manifold that I can't reach easily, so I'm assuming that I won't be able to get at those until I take off the intake manifold.

 

I had a dealer pressure wash my 99 Taco, it screwed up the cruise control and the auto locks. I did not ask them to clean under the hood, they just did it...

 

I clean my engine bay often. I just take care not to aim squarely at wire harness connectors, the fuse block, or the battery. Otherwise, everything gets a rinse and has since the first car wash.

Before I replaced my valve cover gaskets, I had oil all over the sides of the block, and everything below that. I sprayed some foaming degreaser in these areas and agitated them with a medium size brush getting every surface I could. Rinsed well after that. No issues.

 

For fluid hoses I used braided silicone.....Napa used to have by the foot....
but due to supply chain issues....only way I can get it now is by 10' roll....

$38 HPS 5/16" ID blue high temp reinforced silicone heater hose 10 feet roll, Max Working Pressure 85 psi, Max Temperature Rating: 350F, Bend Radius: 1-1/4"

Amazon.com: HPS 5/16" ID blue high temp reinforced silicone heater hose 10 feet roll, Max Working Pressure 85 psi, Max Temperature Rating: 350F, Bend Radius: 1-1/4" : Automotive


For heater hose I went with these....

HPS Blue Silicone Heater Hose Kit for Toyota 95-04 Tacoma 2.4L & 2.7L 4Cyl (ebay.com)

 

As far as washing engine.....an engine will run just fine dirty.....

However when you get water into the engine sensor connectors....
you know the 25yr old ones.....
nothing good can ever come of that......

 

There's a bunch of vids on tactics to clean engine bays.....

In keeping mine clean....there is a number of things I've caught.....few natural failures.....
but mostly things I didnt do right first time....
caught em before the walk of shame.......

And if I get caught in the rain......I always make sure to wash under carriage down at work before the weeks out....
I worked too hard getting all that cleaned and painted......

 

There is one hose I kept factory......because of its weird shape and extreme importance.....

And that is the hose that goes from the EGR valve down to the heater bypass hose.....
that hose sends hot water to egr valve and then on to the iac.....
you do not want a failure in there on the road.....that would be a major pia to fix remote local.....

Toyota 16267-75010 Engine Coolant Bypass Hose

Amazon.com: TOYOTA 16267-75010 Engine Coolant Bypass Hose : Automotive

 

So I've swapped out most of the main ones, but I'm not sure how to proceed with the PCV hose. Toyota doesn't make this OEM hose anymore, and it seems to have 2 different size ports to fit on. The PCV valve looks to be about 8mm and the port connecting to the intake manifold seems to be a couple mm bigger.

Can anyone provide insight into what size I should get? I saw that some people added a custom hose for this one, so curious if you remember how you did it.

 

I have a 98 and I think I used 5/16 clear blue snowmoble fuel line.....its whatever the largest they sell.....
.....I think it was like $9 for a ten foot roll......

It works fine.....the intake nipple is tiny bit larger....

 

5/16-In ID Blue Fuel Line (5 FEET ) ATV Watercraft Motorcycle Snowmobile BIKE | eBay


That pcv valve grommet goes to crap after year or two.....so I always replace it once a year.....

I've had to pick pieces of grommet out of valve cover baffles before......ptsd

And I replace that pcv hose every other year......
Kinda gives me a gauge as to what's going into the intake.....

 

Thanks this was helpful! Was unsure if the 5/16 would be too small for the intake nipple but fortunately it doesn't seem so. Also, I zoomed in on your photo and I don't think I even have a grommet on my PCV value. I have no idea what happened to it but whatever it was probably happened before I became the owner.