Coolant Hose Changes Time/Mileage

I finally changed all the hoses and thermostat on my mom’s 07 Highlander. It has the 3.3 V6. I was pleased to find out that there is a hose UNDER the intake manifold. So had to take the air plenum and intake manifold out. I figured that at 12 years/215k miles I (she) was on borrowed time. There are two hoses which run to the throttle body, presumably to prevent icing in the winter time. I didn’t have these hoses so I bought some bulk hose at a local auto parts store. All they had was 3/8 hose instead of the 5/16 that I needed. So, I bought the 3/8 and used that instead.
Well, being the worry wart that I am, I ended up special ordering the correct hoses/clamps from the Toyota dealer and putting them in a week later. I had clamped the 3/8 good with worm drive clamps, but they still seemed not as tight as factory. So now I can sleep soundly.
I was relating this to a mechanic acquaintance of mine and he said I could have just used 5/16 fuel line hose. This was available at the auto parts stores. He claimed that since the fuel injector pressures are so high (obviousy higher than the 18 or whatever of the cooling system) that you can put them in with no worries. My thinking on this is one, fuel never gets to the the high temperatures of the cooling system, two, I don’t think fuel line is of the electro-chemical resistance variety. Doesn’t that seem correct?
As an aside, I always have kind of stuck with GM products since I have a pretty firm grasp on how to repair them, their weaknesses, parts availability, etc. Having said that, I was really impressed with the hoses on this Highlander. Every hose, with the exception of the upper and lower radiator hoses, had a layer of rubber armor on them. The heater hoses were covered by a protective hose their entire length. They build these things to last. If there was even the most remote chance of the hose rubbing against something it got protected. I have never seen this in my or my family’s GM vehicles. Maybe this is because I mostly buy trucks which are never short on engine space, but still.
While I had the intake plenum off I replaced all the rear coil packs and spark plugs. I had done the plugs at 150k, however, I just had a front coil pack fail on that thing and was SO lucky it was one of the easy to access front ones. I figured I would be extremely upset if one of the rear ones failed after having just had all of that apart. I’ll tell you one thing, those aren’t real cheap, even in the aftermarket. Densos were like 70 bucks at Advance Auto (thank goodness for 20% off). Also, the freakin intake manifold/plenum gasket set is 80 bucks for Fel-Pro…awful pricey for something so thin!! But I have never been done wrong by Fel-Pro before…
Anyone ever sub out fuel line for coolant line?

Yup, no issues at all.

You worried about the temperature resistance since fuel doesn’t get hot… but everything around the fuel line gets hot. The hose is designed to handle inside heat as well as outside heat. The hose is rated to withstand 100 or 200 psi depending on the hose. Higher than the 18 psi water temp. That high pressure rating allows he hose to perform even better at low pressures.

What was the condition of all the hoses you removed? How close to failures?

Ridiculously good shape. Upper radiator hose had some spots approaching soft, the hose thats under the intake manifold had a thermo protective/rub shield that was totally crispy/disintegrated. Hose was fine though. I felt like an idiot for changing them all. But heck, time has been spent doing worse things.

I bet 90% of recent cars never get their hoses changed before they go to the junkyard. I’ve not had to replace any with my cars that I keep for 10-13 years.

The material I see being used for ALL rubber parts over the last 25 years or so seems to be really high quality. That includes door seals and interior rubber bits, too. My first cars built in the 60’s and 70’s would show noticeable deterioration in 7 to 10 years. My 14 year old truck has original hoses and they look great. Only the brake hoses turned to junk.

A 12 year old SUV with 200K+ on the clock deserves some love, though!