Losing coolant but car runs fine

I just bought a '19 Gen 4, so I've been doing a bit of research.
There was a problem with the EGR coolant getting into the exhaust system directly in the Catalytic Converter area.
I think there was a TSB or recall on this problem.
You may qualify!
Good luck!

 

It is not the EGR system but the exhaust heat recovery system (EHRS). Coolant is leaking from the heat exchanger into the exhaust system just in front of the catalytic converter. Very common problem on the Gen 4 Prius. Do a search in this forum and you find a lot of information. This should be covered by the Toyota warranty.

@andy song , Take the car into your local dealership to get it fixed under warranty.

 

That would be covered under the federal emissions warranty 8yrs or 100K miles or you may be able to talk the dealership into replacing it for free, reference the TSB. I don't believe the 2021 model year was covered under that - but it doesn't hurt to ask.
If they refuse to cover it for free; just by-pass/loop the hose at the heat recovery unit, behind the CAT. There's a few YouTube videos and multiple threads on this forum about this. Search 'exhaust gas heat recovery'

Hope this helps.....

 

Bill did you forget your Ginkgo Biloba this morning?

 

No, just new to a Gen4.
Isn't there something about EGR being taken post CAT?

I've had mine for exactly 2 weeks now and loving it!
Still learning the systems and their names....
It's a '19 ECO with only 235k miles on it. So I got it for a song!
The Champ!!



Next I'm buying a Comma for it. That was the driving force to give up on Gen3's.
That and head gaskets. Once is enough.....
But the quietness and improved fuel economy are added treats !

I cleaned the battery fan filter, for the first time from the looks of it, but it was easy and satisfying!
And today the engine oil/filter and transaxle ATF. Mobil 1 all the way! I won't argue about using WS, again...
I like premium lubes !!
And soon both air filters will arrive.
I'll test the engine coolant and then, relax and drive the Hay'L out of it. while I wait for the Comma to arrive.
Are there threads here about setting up the Comma?

Updating my signature soon.
How about that for jacking a thread????

 

Leaking coolant into the Exhaust Heat Recirc system at a high rate needs repair or bypass asap. Otherwise you risk a badly overheated engine and then a head gasket.

 

thanks @rjparker - I guess my memory isn't that bad from old age.
I don't believe Wisconsin is a CARB state.

 

Looking for someone in or near Nashville tn to help me do the heat exchanger bypass

 

For what it's worth, I'm pretty sure that heat exchanger is just behind both catalytic converters.

In a gen 4, the first catalytic converter is built right into the exhaust manifold. The second converter is the first bulge in the exhaust pipe. The next bulge is the EHRS heat exchanger, and there's probably a resonator/submuffler bulge after that.

 

Shouldn't you see if the car qualifies for a free emission systems repair at a dealership first?
There is a lot on info about this system failing.

 

Just look for two black rubber hoses going into one of the exhaust pipe budges; that's the lines you'll need to loop.

 

After you verify Toyota won't repair it free (which could get you a new assembly), I would have any shop with a lift immediately do a below vehicle bypass.

Option 1

Bypass under the vehicle




Option 2

A no lift, no parts required driveway bypass requiring more time.

Bypass in Engine Compartment requires Wiper Assembly and Cowl Removal

Long term a bypassed heat recirc/exchanger should have the internal actuator forced open. However this is not an immediate requirement as an exhaust flow still exists and normally exhaust pressure alone will open the straight through path.

 

Thank you, ChapmanF, for correcting what I wrote in post #3.. I am not very familiar with a Gen 4 Prius and normally do not make posts in the Gen 4 forum.

 

mobile 1 is not a "premium lubricant "
Amsoil is a premium lubricant.

 

And what premium ATF should I use in my Gen 4 transaxle?
I have a jug of Reline ATF D6. Is that considered premium?

 

Thanks for posting this primer on this system!!
I got to take advantage of it this 19° morning leave for work in my '19 ECO.
I feel it did get the cabin warmer quicker than in my Gen 3.

 

Not according to toyota:



Also, while it's not noted in the Owner's Manual, but I did come across a document, likely a dealership service department directive, saying to only use ATF WS from freshly opened bottles.

After doing the bypass?

 

No, my Gen 4 is doing fine. The OP has the problem.... pay attention....
I feel my Gen 4 is quicker to warm the cabin than my old Gen 3.
Technically I have not crawled under the car to see if it's using the exhaust heat recovery system (EHRS).





OH NO,,,
Not the dreaded 'may cause ultimately damage' .....

But let's do this, again.....
WS is the house generic ATF. That's what your 25 year old Tercel uses. And most everything else they drag into the shop. They want to sell their stuff that the parts room stocks.

I choose to use a higher quality synthetic ATF. I have been using Mobil 1 or Redline ATF's in my many Gen 3's for a long time and many miles.
I feel my transaxle is happier and that I'm getting many more mpg using a modern synthetic alternative to WS.

I started a very long thread on testing the ATF that was drained at different intervals.
ATF fluid changes ARE Required. | PriusChat
Dang, up to 37 pages now !!! To be honest, I haven't read them all.....
I got away from owning a Gasser for a few years when I owned a Volt, Spark EV and now a Bolt.

 

IMHO; If your going to run extended intervals between ATF changes - going with something like D1 or Mobil ATF may be warranted, since they resist thermal break-down better than Toyota WS. I recall a YouTube video where Toyota WS placed pretty low, below Valvoline ATF. I believe D1 came out on top, but it may've been sponsored by Redline.
If your sticking to 50K-60K replacement intervals, Toyota WS will do fine. I ran my old Prius C for 70K miles on WS, and it came out cleaner than the 20K mile replacement.
We still don't know if the other stuff will de-laminate the electric winding wires over time.

Your results may vary.........