Toyota Prius Forums banner
1 - 5 of 5 Posts

· Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Happy 2nd owner of a 2008 Prius, 155k miles (bought used at 120k miles). Here's what Im running into:

After about 3 miles of driving, red triangle came on, followed by the coolant temp light. Coolant level was low in the overflow tank, refilled. Light still coming on... oil level was low, topped that off. Still coming on. Not driving it till I figure this out. Additionally, I've been noticing the cabin air takes FOREVER to actually get hot when I turn on the heater... it pretty much just blows cold air all the way to/from work.

From reading the forums, it looks like I should be thinking to replace either thermostat, inverter water pump or possibly looking at radiator fan issue, but I'm not really sure where to start. I've worked on other cars before, but not my Prius. Not sure, for example, how to tell when the radiator fans SHOULD be coming on, so that I can see if perhaps the radiator fan switch or the fans themselves are bad... or how to tell which of the water pumps may be bad (inverter or engine)... ultimately, I don't like paying/trusting the dealer, but wondering if in this case I should.

Any relevant experience / advice appreciated. Thanks!
 

· Super Moderator
'17 C 4
Joined
·
700 Posts
Almost guaranteed that it is the engine water pump.
Fairly common failure on high mileage Prii.

The inverter coolant loop is a whole different thing.

You can test the fans by turning the AC ON. The fans should run.

Since the water pump is electric, the "thermostat" function is accomplished by leaving it OFF until it comes up to the desired temprature. I'm pretty sure that there is NOT a conventional thermostat.
 

· Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Almost guaranteed that it is the engine water pump.
Fairly common failure on high mileage Prii.

The inverter coolant loop is a whole different thing.

You can test the fans by turning the AC ON. The fans should run.

Since the water pump is electric, the "thermostat" function is accomplished by leaving it OFF until it comes up to the desired temprature. I'm pretty sure that there is NOT a conventional thermostat.
Thanks, Easy. I'll be working on this today. Hope to firm up the diagnosis and get the part ordered. I appreciate your help!
 

· Registered
Joined
·
3 Posts
Discussion Starter · #4 ·
Ok, so here are the codes it's throwing: P1121, P1122, and P1116. Looked those up online, seems probable that it's the coolant valve, needs to be replaced. Once I took a look at mine, (after now noticing a nice patch of coolant leak on my driveway that I didn't notice till now) looks like there's definitely something up with it (see pics attached), and I'm guessing this is probably the culprit for both the red triangle of death / coolant temp light AND the no/slow hot air in cabin?

Question: I noticed also some discussion that made me think maybe I should also check to see my radiator isn't clogged... but I'm not sure how I'd be able to do that until after I replace the coolant valve and refill the system (esp since i seem to have a significant leak as well as a stuck valve?), then do the rev/hose squeeze method. Any good way to check before then? Or fix valve and assume no clog? I'm just not real familiar with coolant systems.
 

Attachments

1 - 5 of 5 Posts
Top