Coolant too cold

Happy new year everyone.

I have 99 2wd 2.4L. My coolant will not get hot. I’m trying to get my catalyst monitor to turn on and the tsb says my coolant needs to be at least 176 for the monitor test to start. My coolant at idle after 15 minutess gets to 176. However as soon as my car moves coolant temp drops to 172-174. It’s not that cold here. I live in ca, and it’s been 40-50’s. I’ve driven for nearly 5 hours at the speed needed for the test but apparently since my coolant temp drops below 176 when I move the test will not start.

I changed my old thermostat(year old motorad) to a new 180 degree Murray ultra thermostat from orielly. I swapped the Motorad to make sure it wasn’t the thermostat. They are both 180 degree thermostats.

My coolant is about 5 years old but I’ve only put about 15k on it. I had all Toyota red coolant until swapped thermostats and then topped up with Walmart pink long life zerex for Toyota’s. The bottle said I can mix with Toyota red...

I replaced the coolant temp sensor to make sure it’s reading correctly.

Does anyone have any ideas on what could be causing this?

Air in my cooling system?
Is my coolant too old?
Should I not have mixed coolant types?
Should I get an oem thermostat?


Any help would be appreciated I’m trying to smog it and my kids are getting mad at me because we can’t throw all our junk in the back and go fishing.

thanks

 

Get a piece of cardboard and cover “some“ of your radiator.

 

Make sure to turn the heat control to "cold" (making sure the valve is fully closed, which can be confirmed by checking the return hose which should be cold). In my 2.7 (also 4 cyl) I'm getting 150F within a minute from starting the engine in less than 5 minutes it is at operating temperature 185F.

If your engine is not doing that you have a "leaky" thermostat. With thermostat closed and heater in "cold" (closed valve) the coolant would boil (unless you have diesel).

 

liking your post especially for this

do you have a transmission cooler? How are you monitoring coolant temp?

Welcome to TW and Happy New Year to you as well.

 

I dont think I have a transmission cooler. I am monitoring coolant temp with my cheap scan tool that has live data.


I’m going to be home in a bit so I can try some cardboard and check to see if my return hose is cold.

Return hose would be the lower rad. hose right?

 

I want to say its the hose/line next to the coolant drain petcock... don't quote me on that though

as for an added cooler, you'd known. would look something like this... you'd see it as soon as you opened the hood and looked down.

 

I don't know how it is in 5-lugs (maybe similar) but this is how it looks on my 2.7



The one with a valve connected to heater temperature control is hot, the other is a return hose. This is also called a "medium circuit" - basically running coolant from the engine through heater core and back to the engine.

There is a "short circuit" which is basically a pipe running from a water pump back to the engine - it is used for heating up the engine (bypassing heater core and radiator). The third circuit is used when thermostat opens and then the coolant will flow through the radiator giving maximum cooling.

By the way this is the reason why there is a recommendation when driving through Death Valley in the summer: turn off the AC (so radiator is not heated by AC condenser) and turn on cabin heat on full blast (make the "medium circuit" help with engine cooling.

 

i thought when he said return line we were talking about transmission. what I get for not reading your post.

 

I don’t have trans cooler. There’s no hose attached to the outlet by the peacock.

I checked return hose when the temp hit about 150 it was still cold. Then I rechecked it several minutes later and it felt somewhat warm but it may have just been warmed up by being near the engine. My coolant was still sitting at 174-176. Until I stuck a piece of cardboard on the radiator. Then the temp finally went up. I covered the whole rad at first. the temp went up to 195 quick so pulled some of the cardboard off and then it dropped back down to about 180.

I drove it for 20 miles at 45ish. The monitor did not clear but now I have a soft p420 with no cel.

Can the rear 02 throw a p420. I have a fresh dealer 02 up front.

can a small exhaust leak behind the cat cause p420?

Or am I likely needing to get a new cat?

thanks guys

 

Can't help with P420, but from the cooling symptoms you wrote, you definitely have a problem with thermostat. Either it is stuck open or have very significant leak. Or maybe someone stole it

 

Everyone was right... it was the thermostat... I picked one up while picking up my new o2 from the stealership. I just didn’t want to believe it because I bought a couple bs “premium” aftermarket thermostats. The guy at the parts counter said that many of the aftermarket ones don’t quite get to 180 and over time it causes problems because you’re running a bit cold.

and I fixed the p0420... I ended up getting a full magnaflow exhaust. The wife told me to just replace it so I said ...OK... the old stock exhaust lasted about 21 years so that’s not too bad. It was rusted everywhere and had been repaired a time or two already. Late merry Xmas to me I guess. Now to complete some drive cycle and visit the ole ca smogman.

thanks everyone

 

That's great news to hear hombre
And thanks for checking back in and reporting afterwards. Always nice to have that info here in forum for the next dude that runs into that situation