PLS HELP! Getting 200KM or less after changing Thermostat!!

It's a 2008 Tacoma TRD Sport Tow Package, 4.0L V6

Getting less than 200KM on a full tank with VPOWER Shell Gas and same with the highest octane at Mobil 1. It dropped instantly after changing my thermostat. Truck takes forever to warm up. At first I thought maybe it's the PCV valve so I changed that to a brand new OEM one from the dealership. My old one still rattles and was fairly good. I kept it as backup after the swap. Will change the Spark Plugs to OEM Denso's but honestly, it would be unreasonable to change them when I know the fuel consumption became extremely poor only after I changed the thermostat. I put in the AISIN from Amaz0n Canada. I bought two. One is off brand and the other is the AISIN but I feel like some dbag swapped it with a bad one and returned it(?) because there is no sticker on either of them. The OEM and aftermarket one both look the same I believe and has the same temp rating of 180. I decided to just use the one that was supposed to be AISIN OEM but like I said, it had no silver sticker on it. Since changing it, my truck is not giving me anything past 190-200km. The truck takes forever to warm up and sits dead center between hot and cold. The heater doesn't blow as hot as it did previous years. Is the thermostat stuck open and not getting to closed loop?? Maybe I missed a step on the install?? One of the hoes was lose after driving from Toronto to Algonquin Park. I checked and tighten the clamp and it isn't leaking coolant since but maybe that's the issue? The clamp and hose not being tight enough leading to air leak? I really don't know.

If you guys can help with this, it would mean so much. I have a cross Canada trip coming up and need to sort this out pronto.

 

I feel Amazon is pretty known for selling counterfeit parts.

Do you have any check engine light codes? have to tried putting the old thermostat back in? Is your coolant properly full? What kind of coolant did you use?

What led you originally to change the thermostat?

 

Thanks for replying man. I have no CEL codes. Old thermostat had gone bad and was leaking profusely. There was crystallized coolant on it. My coolant in the reservoir and the radiator is to the top, full. I used pink coolant 50/50, the same I've always used that's recommended. Anything else?

Edit: I should add, when my old thermostat was leaking coolant all over the place, my CEL never went off. Should it have? Is it possible that a sensor for the CEL has been turned off by the shady dealer I purchased it from? Lol probably good to know.

 

Do you have a scan tool?
Can you see your Engine Coolant Temperature or you Fuel Trim data?
What is your idle speed on a "warm" engine?

 

Thanks for responding. I do not have a scan tool, unfortunately. I can pop an infrared scanner on my radiator hoses today and take the digital reading? Is that what you're hinting at?

 

Kind of, yes.
Was looking to see if the ECT is getting over 150is degrees.
I don't think the 4.0 goes to closed loop until then.

As for fuel trim, it would help us know if we are looking at a lean condition being compensated for.

 

I would need an OBDII scanner for this right? The ECT is functioning that's for sure, just because the old leaking thermostat did not cause a fuel drop this bad. I don't know what a fuel trim is but I'm guessing the OBDII scanner would check this? This problem is really messing with my peace and financially-- a big nightmare.

 

I second the code reader, and like TnSHooter mentioned, check how hot it's running at. An overly cold engine in a cold climate will get terrible mileage. There's a chance the thermostat is responding very slowly or not closing all the way or that you got a bad one. When something like that happens right after a repair it's time to look at the last thing that was "repaired".

 

I'm in Greater Toronto Area, Canada. Should I buy a ECU reader then? Or start with the heat check, take out the thermostat and place it in hot boiling water? I feel like the thermostat may be stuck open. Could also be the hose not clamped down tight enough. What should I start with?

 

I don't think it is a hose issue.
Thermostat possibly. As you say it takes a long time to warm up.
The temp gauge on the dash is a poor way of measuring temperature.
It's pretty much there just to act as a warning. It doesn't really give an accurate representation of the temperature.
It basically has three reading. Cold, Some where between cold and hot (Warm-ish) , and Hot.

 

If it were me and I didn't have a code reader I'd drive something I always drive (route) and once I verified it's not as warm as normal at a certain distance I'd pull the thermostat. For instance I know I need to be about 2-3mi from the house in the morning before it's warm enough to ramp up the heater, sounds like you already know the answer to that question. The code reader will be more informative but you'd want it available when the vehicle was cold so you could watch it warm up, running down to the autoparts store and getting it read might not yield much helpful info .

 

You can also pull the thermostat, and put it in a pot of water. Turn the burner on, and measure the temperature of when the thermostat starts to open.

 

I concur with everyone above, only thing different I would suggest it to either take the hit and acquire and install an OEM thermostat or try your hand with the other aftermarket one you already have and go from there. It could be something else but since it happened following your thermostat replacement and I have a large skepticism for parts that aren't from a reputable source like rockauto, dealers, (not usually my first choice but) chain part stores, I would throw what ever you got in the garbage and install a proper reputable thermostat and go from there. If your engine isn't getting up to temperature you need to start there.

"Base" engine issues should be rectified before looking into other areas

 

Yeah exactly. It definitely does warm up to the centre but the issue is on how long it's taking to even warm up. A lot slower than it used to.

Are you saying to pull it out and replace it?

I'm planning on doing this tonight. I'll swap in the second one in the meantime but only after testing that one first in the boil check. I've been planning on doing it.

I'll do a boil check on the second one but honestly, I will be ordering one from the dealership. I really thought Amazon would not be so irresponsible when it came to vehicle parts. That whole organization in Canada has gone to crap ever since they started hiring Indian students. Not all of them are bad but quite a few of them are corrupt in thinking. They've destroyed Amazon like termites as many of them are in key positions as well making decisions. Who knows how many of them are from illegal call centres. Anyhow. I digress. It's not the first time Amazon has done something sketch. I hope and pray to God this is just a case of a bad thermostat or a leaky hose.

ONE QUESTION to you all: IS it HIGHLY plausible that it come be the hoses related to the coolant that was spitting out coolant after the change? My clamp was lose but once I tightened it with a plier, it stopped leaking. Maybe the hose isn't completely pressurized?? Or do you all think it's highly likely its just the bad thermostat that's stuck in the open position?

 

Bump: Any others here that can chime in?

 

Never seen a thermostat leak, only thermostat housings and temp sensors. Correcting that doesn't require a new tstat.

Do you still have the old tstat? Test it on the stove. If it opens when it should, reinstall it. Otherwise get a new OE unit.

I've seen tstats installed with improper orientation that caused problems. Be sure you install the new one correctly.

Your hoses have nothing to do with it. If snugging a clamp cures it, their leaks were from loose clamps.

 

I don't see how a thermostat can cause that bad of fuel mileage, if your correct about only getting 200KM a tank and my math is right that's less than 6 mpg.

What were you getting prior to all this?

 

Absolutely a bad stat can cause poor mileage, engines run richer than normal when cold.


Forget about testing it in boiling water. Right after replacement your mileage went to shit, you lost heater performance and the gauge is reading way colder than normal. That's the test right there..It's bad, try another one. Preferably OEM

 

Is it possible that you put it in backwards?

 

Not to be a smart ass but are you sure you did not put the stat in backwards? I've seen that done before. If you are sure it is the stat, then pretty much seems you need to pull it out and make sure it is in right, and if so that it is operating correctly - pretty simple to do with a hot water test. Good luck.