P1121 CEL-RTD and coolant spray

I just got the CEL, specifically solid yellow exclamation and intermittent red triangle of death (RTD) light about ~10miles after an after anti-freeze draining and filling of my 2005 Prius [baseline, 128k miles]. Antifreeze is topped off in the radiator and overflow container and I feel pretty confident the hoses were burped as I ran the fan and heater on high in a parking lot. The OBD2 code reads P1121 Accelerator Pedal Position Sensor Range/Performance Problem but I imagine it's more the coolant system malfunction indicated on most chat threads. I have been reading through a half dozen P1121 PriusChat postings and all pointing to a normal malfunction at +100k miles and a simple need to replace the coolant control valve; so I have OEM part on order now. As I inspected the engine compartment, I noticed a very dripping wet coolant control valve and areas surrounding it. Liquid was definitely coolant. It looks like the coolant originated from larger coolant hose above. Could this be due to an excess of pressure in the coolant system [perhaps failed coolant control valve] forcing coolant out of a hose clip? It could be a pin hole in a hose that only opens with the increased pressure, but the hoses look in great shape. Any thoughts here?

I reset the CEL and took the car out a second time to replicate the spray: nothing at low <30mph speeds mainly noticing electric battery usage and with minimal gas engine usage-- no CEL; but same coolant amount of spray was noticed at high speeds [~60mph] with gas engine engaged and CEL-RTD revisited. No signs of liquid gurgling and squeezing hose pressure was ok without any pressure/stiffness.

I am reading that I can still drive back roads [under 45mph] the Prius with the CEL for a few weeks 'til I get it fixed. Is that correct? My concern is that my added symptoms of leaking coolant with the RTD
(unlike the other chats) may nix even under 45mph driving.

cheers

 

JC91006. Thanks. i relook at tightening up the control valve hoses, but they all are pretty set up against limits.

OK, I relooked at the coolant air drain valve that has a 6m hex head. just beneath it under the upper-grill cover is
an extended drain pipe with no apparent attaching hose; it looks like it needs to be attached to something. Could this be a place where i am leaking coolant? I cannot find anything online nor on PriusChat to ref this pipe?

cheers

 

Andrew,
You are awesome!
i TOTALLY didn't properly bleed the coolant... Correct, I bled the engine coolant and not the inverter system coolant yesterday whilst squeezing my hoses, and air bleeding the upper coolant valve.

In this regard, I am a total sloppy-amateur. I FORGOT to noted that i did receive the engine temp thermometer overheat icon on the upper left corner of MFD. Thus the RTD did in fact derive from engine overheating. I don't recall it being an exclamation mark and car, though. WORSE, I forgot to incorporate the CHRS pump technique, I woefully overlooked these important Prius-specific steps. I was incorrectly thinking of maintenancing regular engine cars.

OK, but today's time in the shop was very productive in regaining on yesterday's losses. I incorporated the CHRS pump with a paperclip... nice! That enabled me to slowly and thoroughly level the air pocket bubbles in the coolant system. I located origins of the spray issue; it was more small drain spigot connected below the upper coolant valve. I contained it with a clear plastic upward pointing hose;allowing me to monitor air escape and coolant fill.



In later stages of incorporating the gas engine to cycle coolant, the engine didn't activate for long and quickly reverted to battery engine idle; that reassured me more that i was going in the right direction and Prius could better self-temp regulate. Driving it home ~7miles in the cooler evening under 40mph didn't draw the CEL nor RTD. In fact the CEL self-cleared this morning. However OBD2 code P1121 is still prevalent; hence my continued hesitation from going over 40MPH and total effort to avert another overheat. I would've thought the CHRS pump should've resolved the RTD-overheating issue? Any thoughts out there. I still have a new coolant control valve coming in the mail; with that lingering P1121 code, i figure that will be my saving grace.

Tomorrow i shall get a new $3 radiator cap, just to cover all bases; as the shop and my friends dont have a smaller radiator cap pressure testing pump. I was extra careful around the radiator and fans, thanks. No pets as i operate in a professional car hobby shop.

cheers.

 

OK, i still have a few more days till my part (control valve pump) comes in; until then i will cont to explore & tinker with the radiator system.

So because i cont to drive no greater than 40MPH, the coolant system is just not stressed enough. Seemingly, i can do this all year, as long as i keep the coolant topped off. The CEL cleared itself on day 2 and has not returned. However, the RTD return only but for a quick moment as i climbed a good hill enroute home at 30mph on that 2nd day. Still the RTD too has not returned since then. Overall my dashboard is cleared now; but deceptive as my OBD2 still reveals a P1121; even on day3. This is tricky as its masked as a false negative CEL reporting on my dashboard. If i wasn't paying attention or did not know any better, I'd be stranded on the hwy with an overheated Prius.

All day today that upper radiator drain spigot was still spewing out all over the coolant control valve interior. I need to contain this spillage mess if possible. I can only guess at how much coolant i trail while driving.

ANDREW with your suggestion, I changed the radiator cap for a generic $9 at AdvAuto; its been a good long run at 128k miles; good-bye old'cap. Also i placed a temporary 1/4' hose loop to help both capture some of that coolant and control a cleaner discharge. It may have made the difference, as i took the car up to 50MPH for a mile and no coolant spewed from the spigot. I'm done for the evening and enough stressing the Prius for one day. I will start again fresh tomorrow, spring boarding from today's gains. I'm feeling pretty positive and encouraged with the Prius; enough air was recent bled out of the system with the CHRS pump action i conducted via the paper clip hack to prevent it from overheating any further. I shall check the overflow first thing in the tomorrow morning when I plan to stress Prius a bit more: attempt 50MPH for a longer stretch of distance and if successful i may consider taking it up to 60mph.



BEFORE (50mph test drive)


AFTER (50mph test drive; looks like only condensation as no coolant got trapped in that loop)


Good thing its Spring and won't need the heat switch. On the contrary, my engine emission is great at over 55MPG inner city; but when you're doing ~35MPH everywhere, avoiding highways and at +twice the time cost; me-thinks the time kinda outweighs the MPG gains and I could settle for ~45MPG avg.


With the upcoming coolant valve procedure, its my intent to contain the coolant as i just filled it. I'm still on the fence with both pinchers and drain-capture coupled with a 12" long needle nose plier action. Still have a few more days to be talked into or out of' it.

My inverter coolant looks really fresh pink. Can a standard acid strip test reveal need for flush better than an optic review?

cheers.

 

Its still a bit early to tell, but seemingly the coolant leak (spigot under the bleeder valve) recently ceased after swapping a new radiator cap from this evening's 8mile drive home. My intention was to confirm and replicate today's evidence. That bleeder valve (6mm hex) has been closed shut during the procedure. Like i said, its still a bit early but i think the new radiator cap did the trick. Your concern has me a bit thinking; take it slower and perhaps i can just do another similar stress test from today.

Yes i did see that technique (valve -tube to radiator fill) referenced in a repair manual and on a few YouTube vids. Thought I'd use it towards tidying up the engine compartment. The earlier coolant sprays were just getting to be a hot, wet, mess.

Big thanks.

 

OK, today's 60mile roundtrip to work and back was fruitful.

- DRINK UP. the AM radiator inspection was nice and dry, but thirsty. I poured ~0.5gallon of coolant into the radiator valve. There were no wet spots under the Prius. So I'm thinking that sometime in the night the radiator cooled down and soaked up that half gallon deficit. Because i do recall dropping some sips of coolant into Prius during yesterday's cap swap and hose insert. Could this be day 2 residual effects of radiator still trying to establish equilibrium after me paper clip hacking (thanks Patrick Wong) the CHRS pump? Gratefully, the engine compartment was a whole lot drier at end of today's drive.

- CLEAN DRIVE BUT LESS RESPONSIVE. generally no leaks all day, as i took the car an avg of 40MPH over 60miles, but also peaked once at 50MPH for <1mile. Experiencing less responsive breaking and throttling; weird no engine pangs nor any put-put jerking. The braking is early on the pedal and gas pedal is slower to respond and harder to press.

 

The splash guards are in place. The overheating seems so long ago. I will check out the oil. Look into a engine compression/bleed test. Those are some daunting thoughts, but little to go on.

cheers.

 

4/16/17
OMG. I finally figured out the overall problem: NO O-RING TO THE REPLACEMENT AIR VALVE. Long story short, [I might had earlier left out that] I had lost this valve while working during my initial radiator flush. I had this replaced via mail order but the company didn’t attach an O-RING. Thus I had been riding around town without a clean valve seal all this past month, all the while spraying fresh hot coolant into my engine bay compartment. Now with the new O-RING installed, all coolant sprays have ceased. CASE CLOSED.
***I feel like a total moron as perhaps my $67 replacement coolant control valve was for naught; as that was associated with the inverter coolant system. And the coolant sprays were akin to the engine coolant system. I totally missed that.
*** LESSON. Prius coolant systems are two-fold (inverter/engine) unlike reg cars; differentiating between both systems during diagnosis is key.


4/15/17
OK, returning from a few weeks out of town with the mail ordered new part-- coolant control valve. It looks a bit different in size but 3 tube leads are size and positioned well.


Andrew with your advice, I tackled both engine and invertor coolant replacements--- BUT at the same time concurrently. BIG CHALLENGE, but I nailed it at 4 hours. Instead of the OEM Toyota coolant, I used Peak Auto 2x gallons of Peak anti-freeze Long Life coolant premixed 50/50; claims appropriate for all car types and it doesn’t void all car warranties. After the repair and driving a day the CEL disappeared; however on 2nd day, I’m still getting OBD2 codes: p1121, p1150, and a new code p1118. That last one arrived upon replacing the inverter coolant fluid.


JOB ENGINE COOLANT. I did a completely new flush of the engine coolant system. This would actually drain all of the mixed old-new coolant fluid from my earlier-first botched attempt. To recap, I didn’t fully drain and fill the coolant correctly, and also didn’t cycle fluid via the CHRS pump. In fact I may have only replaced 0.5gallons of new fluid. Ok for this attempt, I drained ~0.5 gallons of coolant and topped it with ~1.5gallons and used the paper clip hack to cycle coolant thru the system. I also used a ¼” clear tube to connect both the bleeder valve spigot and refill valve. Fluid never connected from spigot to the refill valve.


JOB INVERTER COOLANT. Draining and filling 0.5gal of the inverter coolant was a snap; nice pink looking fluid going out, but upon closer inspection plenty of particulates. New green fluid going in. Drained that concurrently as I did the engine coolant. I picked up the car at 90k and it’s at 129k now; time to replace the fluid.


With fluid drained, it was time to replace the coolant control valve. I went in through the driver side head lite, as it gave me so much more room and cut time. Opening that up only took an extra ~5 minutes. Doing that allowed me to see better into the fender frame, and to unveil some mangled metal from an earlier owner-accident. I got a longer set of needle nose pliers as well; man those were NICE. Should’ve had a set of those in my tool kit long ago.


Both nut/bolt were in there rested tight so I let sit a bit of penetrating lube oil. The side-bold I released while working from the bottom of the vehicle. I removed the old coolant control valve through the bottom and placed the new through the top; the newer valve had all the same needed valves, but was just a bit thinner.

Side by side comparison didn’t really show any valve stuck/malfunction or left open; perhaps issues reside internally within the housing. Didn’t bother looking I just trashed the old coolant control valve.


New coolant control valve in—time to refill inverter fluid. I redirected that ¼” tube from the engine radiator to the inverter refill valve and air drain spigot. Now that fluid filled and arced full with air bubbles back into the refill valve. That was cool. By pressing the car start button twice, initiated the inverter motor to cycle coolant fluid and rid air bubbles throughout the system. I turned off the start button when all air bubbles ceased to arc into the refill valve. Afterwards, I looked into the opened cap and saw a small amount of waves and nice humming from the inverter pump. Sounded done to me; good for another 50k miles.

 

Thanks JC.
- NOT a lot of reporting out there on use of alternate coolant fluid options that prove positive. I will be able to report to the Prius community.
- I'm always trying to cut costs, i hope not at a huge expense this time. The Peak Auto anti-freeze Long Life coolant premixed 50/50 was going for $8/ea at my local car shop.
- I'm also purposely assuming more risk and experimenting a lot more with this project-car. PEAK claims its appropriate for all car types and it doesn’t void all car warranties. I will let the Prius community know how this pans out.

Cheers