4th Gen DIY heat exchanger bypass solution

Here is even more simple way how to do the bypass (in the engine area):

 

a pic from ebay used part - looks like one of the old (part #s depending on your model) 17410-37852, 17410-37850, 17410-37AD0
selling for the same price as the new (superseded) part # listed in the TSB 17410-37D40 from toyotapartsdeal at $826 + ship.





those guys at GM are incredible. gurgling muffler bomb - love it ....

 

It's funny though, not 30 seconds in, he says the "problem is the catalytic converter", when the thing that leaks is the EHRS exchanger, which comes after both catalytic converters.

Then right after the muffler bong comment, he goes under the car and says "so here you have the catalytic converter" while pointing to the sub muffler ... which comes after the EHRS exchanger, which comes after both catalytic converters. And describes the coolant path after leaving the exchanger as going "back to the heater core" when in fact it's the other way around: the coolant fresh from the heater core is what gets sent down to the EHRS. That ensures it's as cool as possible when it gets down there (having given up heat to the heater core), so that it will pick up as much heat as possible from the exhaust. It then returns to the engine water inlet.



I suppose Gasket Masters specializes in head gasket jobs, so they'd have a better grasp of the anatomy that goes with that job.

The thing about the explanation he offers for why it starts leaking (cold coolant going in a hot [he says "catalytic converter" again], causing metal fatigue and cracks and leaks) is that the same explanation would completely apply to the EHRS in Gen 3, which has never turned out to be a common leakage area, even in really old Gen 3s.

There has to be some explanation for why it only became a problem in Gen 4.

As for bypassing it, because of the way the heater core/EHRS path is in parallel to the EGR cooler/EGR valve/throttle body path, doing a plain bypass as shown may steal some cooling from the EGR cooler and valve (and some deicing from the throttle body).

A person might think about doing the bypass in such a way as to have about the same flow resistance as a good EHRS exchanger.

 

His rerouting makes sense though?

 

If it were me, I'd want to include in the bypass a bit of restriction, for the reason given in #23 (which I was editing, maybe while you were posting).

 

check out @GasperG post #10 ( the last post on page 1 of this thread ).
Even if GM workaround is not as well thought out as perhaps it could have been, it's a far cry from getting the work done on ones own dime from a dealer, especially if GasperG s quote for the price of the parts ( 3 of them the pipe (all inclusive resonator, heat pump and cat ) and 2 gaskets according to the TSB ) which would you choose in a pinch?

 

His solution is easy enough to do on the side of the road. Almost need no tools at all to accomplish this. I'll be doing this, if/when mine goes.

 

FWIW, if anybody with a Gen 3 happens to read this, the same approach would not be good in Gen 3. In Gen 3, the parallel path through the EGR cooler comes off a tee in the side of that pipe going down toward the EHRS. So doing the bypass up at the top like that, in Gen 3, would mean no flow to the EGR cooler.

The slightly different Gen 4 plumbing allows this to work, though I'd still want some resistance added. Bypassing up at the top of those pipes creates an even lower-resistance bypass path than you'd get with a hose down at the bottom ends.

 

I was thinking about this a little. Basicly there are three things in parallel:
- Cylinder heads/blocks
- EGR valve
- Exhaust heat exchanger

Basicly you could disable the last one by just pinching the hose and everything else should be circulating with no problems. Am I correct?

 

It looks like, in Gen 4, the same parallel path that includes the EHRS exchanger includes the heater core also.

If there can be cold weather where you are, you might not want that path completely pinched off.

 

Should be able to find out really soon if the heater core and the heat exchanger are in the same line, if you live where it gets below freezing. I've already been thinking about duplicating the GM workaround, just in case it ever happens to my car, I just don't want to stress the exchangers by doing it, so maybe not while it's below freezing out and there is a backorder mentioned besides .....

 

How soon you wanna know?

 

Yesterday ?
I'm going to look through what I have of the repair manual, to see if I have one or both cooling lines already.
Hopefully I'll also get a chance to organized all the things I've accumulated so far.

 

Just got a word from the service guy, it will be changed under waranty.

Interstingly, I've checked also if Corolla and Camry hybrid have this system and generaly they don't, but some versions do, don't exactly know where.

 

they may have different types of heat exchange systems, I think the Prime heat pump a more advanced type exchange system.

How were you driving the car before the smoke and coolant loss, mostly highway? using heat in EV or HV or both? typical temps for A/C and winter heat? Any clues why the exchanger cracked?

Glad to hear Toyota is fixing it for ya.....

 

Very little highway, but some hills and more or less 20 km trips in one way.

 

how many miles were on your vehicle? I'm wondering the mileage on the warranty or if there is some kind of TSB that extends it past the usual 60K or even 100k. I'm at almost 110k, so I'm sure no warranty will be available if something happens.

 

TSB 2017 Toyota Prius Prime heat pump

https://static.nhtsa.gov/odi/tsbs/2019/MC-10166037-9999.pdf

 

Someone commented on the above video and said they have just had theirs done under warranty.

Initially they were told it was a head gasket failure, but when they mentioned the TSB they replied to a comment and said "... had mine fixed for free at dealer. Covered under federal emissions warrantee 96 months or 80k. I had 79,500!"

Hope this helps.

 

Jesus, that's tight. Ideally it should be 100k miles. Wonder what limited it to 80k miles?