lexixel

Hi,

I noticed that the vacuum hoses in my engine (228k km) may have "swollen?": they don't fit tightly on the nipples anymore.

Today, I cleaned the VSV for EVAP with isopropyl alcohol. Turns out the VSV was very clean / no need for cleaning. While I expected difficulty pulling the vacuum hoses, they were very easy to pull off.

Perhaps at some point it'll be a good idea to replace at least the easiest ones. [Chart: https://www.amayama.com/en/genuine-c...2/engine/1708]

Anyone knows their size? I think there may be two sizes at least. The EVAP ones seem to be 6mm inside / 10mm outside. There may also be 4mm and 8mm ones?

Thanks

NEWONE1

If you have a caliper just measure the OD of the nipples giving you the ID of the hose...good luck

digitatc

10mm inside dia for some and 8mm inside dia for other. I bought 10ft (3.3m) roll for each.

lexixel

Thanks for the info. No 6mm? I kind of measured the hole at the time (with my phone, as I didn't have anything else on hand). It looked like around 7mm, which is why I have doubts.

I've certainly get some 10mm and 8mm ones.

oneround

There are a couple of 6mm ID hoses in the emissions system. One being over on the VSV for OBD canister (right side of engine - part of air inlet).

I gave up trying to find all the sizes, and was too cheap to pay dealer rates for hoses so I bought a bundle of silicone hoses from Amazon (4, 6, 8, 10, 12, 14mm - each about 7 feet long). Now I have some left over to use with our other vehicles when those hoses get hard.

I did buy the PCV valve and hose OEM.

lexixel

Indeed. The price difference can be huge. It's possible to get all these hoses (silicone) for the price of one small piece of OEM hose.

Wilson2000

If silicon is better than rubber, why aren't manufacturers using it? I've read it is better at resisting heat and won't harden and dry out like rubber. Is there any downside to silicon vacuum hoses?

oneround

Silicone hoses don't do well in continued contact with fuel or oil as they are permeable to fuel, oil and water vapor (but not liquid water). Hence no fuel lines, oil (engine/transmission, etc.) or radiator hoses should be in silicone without some sort of liner. They may be seen more often in racing engines, but those get so much attention that shortcomings are negligible.

I used an OEM hose for the PCV line as that line tends to get "oily" (is that a word?), and I prefer not to have that mess collect on the intake under the engine cover..

If an emission vacuum line were to have a dip such that fuel could collect in a pocket, any fuel dripping out could/would become a fire hazard. OEMs can't really afford that. And if I was still a working mechanic I wouldn't use silicone for a customer's car either. For myself, I did for two reasons. 1) The car gets driven enough I'm not worried about fuel vapor collecting in any quantity in a line, and 2) I have the arranged the lines such that there is no dip where condensate could collect.

lexixel

That is interesting to know. So why not use rubber fuel hose for the EVAP system?

LeX2K

Silicone vacuum lines don't last worth a damn they dry and crack. The best by far are from Toyota I'm told these are neoprene rubber whatever the material these are they last for decades. They are not affected by motor oil, brake fluid or any chemical that I know of. I use one for brake bleeding it has held up no damage, I use brake cleaner, acetone, lacquer thinner, carb cleaner or whatever chemical I have on hand to clean.

Wilson2000

Thanks LeX2K for Toyota part numbers on the OEM vacuum hose! I've been driving and working on Toyotas since 1980. The only vacuum hoses I've had to replace were on 197X's Celicas. I've never had to replace any of the hoses on my 1985 MR2, not even a coolant hose!

If I ever have to replace vacuum hoses in the future, it will be a tough decision to switch to silicon considering the great experience I've had with OEM.

oneround

Interesting note on MR2. I had the 2nd (1991) and 3rd gen (2002) MR2 cars and zero vacuum line problems. Did have the transaxle die on the MR2 Spyder, but that was the only thing other than routine maintenance either car ever required. And not long ago I sold a 2000 LX470 that never needed a vacuum line change -- and on that truck I swapped out the starter motor (under the intake).

But, I'm (hopefully) finishing up an emission/vacuum issue on the 2002 SC430 I recently bought.

I believe my replacement will be the third set of vacuum hoses on the car. First the as built equipment, and second, an OEM replacement set put on in October of 2014. Now maybe the Lexus tech down in Miami lied to the original owner (this was a 1-owner car), but, I have a written copy of the service record. Hence I am going with the silicone hoses in what I consider appropriate spots.

@LEX2K2 I noted the shortcomings I know of for silicone. Under what conditions did you see vacuum lines dry and crack like virtually all the OEM lines do? Silicone has been used for vacuum lines, spark plug cables, etc., for decades. Mercedes and BMW have used silicone vacuum lines. It's been years since I worked as a mechanic (except as a hobbyist), so I can't say if they still do or not.

@lexixel I suppose fuel line would work (at least I can't think of a reason why not), but they are reinforced to withstand internal pressure. As such that they don't bend easily to fit where they need to go, and tend to kink if bent too sharply.

EDIT: I'm wondering if being parked outside with South Florida heat & humidity, plus the heat retention of the engine cover, contributed to premature OEM vacuum line deterioration. Anybody have a good idea?

lexixel

Very interesting information here. Indeed I find the vacuum hoses on my car (228k km) has held up reasonably well. They are still somewhat flexible and haven't thrown any codes.

I'm thinking about replacing some because they don't feel tight on the nipples (possibly swollen). I'll at least have some hoses in handy in case some develop cracks.

I used to see smaller diameter vacuum hoses.

LeX2K

silicon=sand
silicone=type of polymer

Just wanted to clear that up.

When I say silicone vacuum lines I'm making a guess, I think that is the material. I know people that bought "silicone" vacuum lines replaced every one under the hood. They lasted a few years. Maybe they were not silicone, they felt and looked like it. What happened is they swelled at the ends and dried out, no more tight fit. The Toyota ones in the image I posted never do this in my experience and are not especially expensive.

oneround

Thanks for the description of failures you saw. I have never seen that happen. But for sure I will keep an eye out for similar on my car.