4th Gen DIY heat exchanger bypass solution

Bypass down below at the cat actually seems easier, no? Bc wipers, cowling, etc all have to come off to bypass at the top by the engine? Can anyone comment as to which bypass method will keep the car running longer?

 

As far as CA smog check… I’ve never had a smog tech do any in depth visual inspection ESPECIALLY with a Prius. Even if a smog tech noticed this, it would still pass imho. No open monitors, no active CEL, no visual smoke. I have a 99 montero 4x4 snow beater and I installed anti foulers on the post cat o2 sensors and thank the gods the smog tech hasn’t seen them!

 

I am considering your solution to this heat exchanger problem. Did you get any error codes that you could link to the bypass? Are there any sensors that I should be aware of when I do the same bypass? I hope that after 40 000 miles if there was an error code you must have seen it.

 

Don't take this the wrong way; but the only opinion that matters is that of the smog tech signing off on the car. It's great that you've found a smog station that's really 'chill' on their inspections.

 

Toyota's (abysmal, self-serving) response to this issue doesn't seem to have attracted much attention from North American regulators. The fix is in?

 

Sad that even independent repair shops in California refuse to do this job :-(. My jacks and stands won’t get the car high enough for me to do the repair here in my driveway :-(!!! I can get my hand on the hoses, but don’t feel confident that I can get the new U hose on. I usually pick the car on the outermost points behind front wheels, via the skinny “teeth” that stick down. Anyone recommend a different weight rated point to pick from that is lower, and will thus get the car higher?

I def have a bigger jack, but it’s too big to fit under the car to begin with.

 

I pull my car up on rhino ramps, then use my floor jack on that engine cross member tucked way back. Make sure to secure with jack stands and block the rear wheels. That's how I was able to install my CAT shield.
Don't forget to lower the car back onto the rhino ramps or you'll never get your floor jack out.

Good Luck...

 

hey biomes, did you bypass yours at the top end? If so, any issues? I’m tryna get another 150k worry free miles. I bought some spark plugs that I’m gonna install while cowl and wipers are out. Anything else I should hit while the cowl and wipers are out? Car is at 152,000 miles, and is 52k late for the new plugs I know ;-)

 

Hey I’ve watched the gasket masters video from early in this thread. Am I going to get sprayed with coolant? I like the video it’s quick and to the point, and skips the whole cowl and wipers which I’ve done way too many times. Does he also skip the part where he drained the coolant first??

 

Didn't bypass mine, it's still under CARB warranty. That issue is predominately on 2016-2017 model years; hopefully I won't have to deal with that issue.

 

yeah I have a 2017 and a 2020, both primes. I did the top end heat exchange bypass today on the 2017. I started her gas engine up, no issues but that was just idling in my driveway…gonna do spark plugs tomorrow, put her all back together, and then my daughter has to take the 2017 on a 200 mile trip…

as I did the top end bypass, there was no coolant spraying everywhere, just a little steady drip from the metal hose that I capped.

 

Make sure she looks at the coolant bottle at every stop along the way and put some coolant or jug of distilled water in the car for top offs. Levels may go down a bit, while working air bubbles out of the system, but you shouldn't have to top-off more than a couple of times - if you nailed down the leak.

Good Luck....

 

If for some reason you let it drop and the engine overheat, that could be quite a big bill to pay. I wouldn't wait and do the bypass. No reason for the reservoir to be empty in the first place so something is afoot.

 

If you do stop n go driving in sub freezing climates you're gonna want that heat exchanger working correctly

 

I use different jack stand points, albeit on my gen 3. 4th gen might be similar. See the oil change link in my signature (on a phone turn it landscape to see signatures).

 

I'll do my best to be gentle about the heat exchanger thing from a point of adding efficiency to the EV systems.
It's a nice addition when temps are above freezing, but below freezing you've gotta due some mafhs about how much or little of a gain your gonna get from it, keeping in mind at 14 F there's nada.
On the other hand HV modes heat is always available, even if it takes some experimenting to figure out how to use it with hyper miler efficiently. The Primes heat exchanger is sure not a cold weather heat exhanger, if it was it would probably take up all the room in the cabin besides the drivers seat, be a complicated as and cost as much as the Prius.

I had another video in mind but couldn't find it today that was about a homeowner in UK that was unhappy with the new heat pumps performance in cold weather and what the dude he hired to fix the problem installed to raise the performance level to the homeowners expectations. Complicated, expensive and sprawling is an understatement. And rated at 500% efficient.

As this guy tries to explain, you be the judge.

at 3 minutes in that turbo boost electric supplemental heat option is explained a bit to mildly IMO
"normally electric resistive heating is a bad idea, but these guys do it a bit differently" Ah Ha !
At least he mentioned it, but than, Oh well, see our bad different idea !

 

It shouldn't matter, if the thermostat is working properly. If it's stuck partially open, yes you'll have an issue keeping the cabin warm.

 

So far so good… it’s been a week now since the leaking heat exchanger was bypassed, from the top, on 2017 prime at 152,000 miles. Coolant level has finally normalized . Just fyi, I don’t think I mentioned this in earlier posts, but I 100% visually verified that pink coolant was dripping from the exhaust. I didn’t just decide to do this preemptively. I also changed spark plugs while wipers et al were removed. Again, after a week all seems ok after 500+ miles of driving.

I noticed that the heat/ac was set to “eco” mode, and I can’t help but think that at least with heat, the “eco” mode has to be this heat exchanger? Needless to say, I took the hvac out of “eco” mode.

I’m in SoCal, up in the mountains at 5000 ft. So we get snow, ice, and freezing temps, but drive five minutes and you’re in the desert. So never gonna do stop n go in sub freezing temps.

 

yep I had to change out the 3 way coolant valve on my gen2, and I did it without draining the coolant, so I’m pretty familiar with the tediousness of checking and refilling coolant to normalize it on a prius. BUT I don’t recall seeing any mention of the refill process in this lengthy gen4 heat exchanger bypass thread?

 

I don't know what kind of coolant tank is on your 2017, but my 2021 isn't a flow thru. A flow thru coolant tank has what looks like a heater hose at the bottom of it - (coolant intake to coolant circulatory system), an old style suction coolant tank doesn't.
The difference here is a flow through system will 'burp' itself, so all you have to do is look at the coolant level, thru the bottle. An old style suction coolant recovery won't.
An air bubble may form at the top of the radiator cap, preventing the transfer of coolant in and out of the reserve bottle. You'll need to remove the radiator cap to make sure there's no air bubbles there. Top-off as necessary. On mine, the radiator cap is right next to the bottle, higher than the engine level, so air bubbles should make it's way there - theoretically... I haven't dug-in to see if there's some sort of bleed valve somewhere (gen4) - perhaps someone else here knows????