So the wife tells me the check engine light was back on the other day. We went out tonight and the check engine light was off. The last few times it has been on and gone off on its own is when the weather has been really cold (daytime temps around freezing, nighttime temps below freezing) and then warm (daytime and nighttime above 40) within the next few days. When I had it checked before, it had a P0128. The T-stat was replaced about 6 months ago and the engine temp seems to be normal. I don't think it's the T-stat again. Any ideas? Sorry if this is a newbie question.
Check Engine Light Confusion
- Thread starter TNEnvoyXL
- Start date
gmcman said:
Haven't had the most recent codes checked. Figured it would be the same since it came on and went off like it did before. The weather this week has followed the same pattern as I mentioned above.
OK I got the code red and I was right . . . P0128. So either the T-stat is bad again after less than one year and/or the coolant temp sensor is bad. When I took the car to get the code red, I noticed the temp gauge red anywhere from one tick to two ticks to the left of 210. So if you guys recommend replacing the T-stat should I also replace the coolant temp sensor? The car has 128,xxx miles on it. Let me know your thoughts.
I would do both at this time because they're adjacent, but what brand did you put in last time? Best to not delay any time you see a running temp gauge at all to the left of 210, even before you get a code, because it's costing you fuel and putting the cat at risk.
the roadie said:
Not sure what brand was put in. I had a local mechanic put it in (I know but I was limited on time). I checked and it would be replaced under warranty. Since they are there I will probably have them put the coolant sensor in IF it isn't too expensive. What brand do you recommend?
I agree this is costing me fuel and putting the cat at risk. Fuel mileage average has been around 16 ~ 18. I know the average will vary but what should I expect the average range to be if all is working properly?
TNEnvoyXL said:
On the two thermostats I changed, it had the degrees stamped on it. Do not use the 186 deg (STANT) I went with Motorad 192deg (this gave me a 195-197 temp.) . If you could get one 90 deg, might be perfect. Coolant sensor it about $25. 16-18 with XL, I'm going to go ahead and call you a liar
You would get that if all is working well.So I had the car checked today and my mechanic said my problem is actually the fan clutch and it needs to be replaced. Said it would be about $650. Does this sound right? I just want to be sure before I spend more money on this car. It's starting to drain us financially.
Mooseman
Moderator
A P0128 would not be caused by a bad fan clutch. Your temperature is below what it should be because the thermostat is not regulating it properly or the sensor is bad. Doesn't matter how much air passes through the radiator, the stat should be keeping the temps where they should be no matter what or the sensor is not reporting the temps properly. Bad fan clutch would throw different codes and usually gives other symptoms than low temps.
Find yourself another more competent mechanic and get the stat and sensor changed.
Find yourself another more competent mechanic and get the stat and sensor changed.
Mooseman said:
They told me they checked all the codes and said they found the fan cluch code but when I had it checked at AutoZone they only found the P0128 code. So I agree I need to have a second opinion. What really sucks is I have used these guys for quite some time and have trusted what they have told me. Oh well.
gmcman
Member
- Dec 12, 2011
- 4,656
TNEnvoyXL said:
Generally the Autozone employee will be right there with you and you can verify the codes...I believe they even give you a printout. Your fan clutch may be on the way out but that's not your issue, your issue is the coolant that's LEAVING the block which is too cold not the coolant flow RETURNING to the block.
P0128 is when the coolant is too cold in the block from not being alowed to remain in the block, because of a bad thermostat or bad sensor, generally a thermostat. Like Roadie stated, they're right next to each other so replace both.
gmcman said:
This is why I am getting a second opinion.
When I picked up the car the guy behind the counter told me the fan clutch was stuck "on" so that the fan is on all the time. This is why the temp is cooler he said. We just got back from a short vacation trip and the car averaged 20mpg and the temp was one to two tick marks to the left of 210. If the fan is stuck on all the time would I still see good mpg and lower temps?
Also in some other reading about replacing the fan clutch there was mention about checking for play. I gently pulled the fan up towards me and there was a little play but not much. Would this also mean my water pump is getting ready to go? No noises coming from this area. Just trying to understand what I'm up against.
gmcman
Member
- Dec 12, 2011
- 4,656
TNEnvoyXL said:
If the only code that was pulled was P0128, it has nothing to do with your fan. Let me explain this another way.....
You can put 10 fans in front of the radiator, it won't matter. The temp gauge on your dash lets you know the temp of the coolant in the engine block, not the radiator. When the thermostat opens, the hot coolant will leave the engine block and enter the radiator, the temp sensor is in the block, before the thermostat. thus displaying the temp of the coolant getting warmed by the engine.
When the thermostat goes bad, it won't completely close, thus prematurely allowing a circulation of colder coolant back into the block, displaying a lower temp on the gauge. The water pump will always pump coolant regardless of it's state of health...it will leak when it starts to go bad or make a failing bearing noise....but will always pump if it's turning. When the thermostat is closed, the pump will move the coolant elsewhere but not out of the radiator.
The guy probably heard your fan engaged and thought it was your issue, it's not. When the temp climbs a few ticks past 210, then the fan is likely the culprit.
I would pick up a sensor from the dealer, and a trusted thermostat with a 195 deg opening temp. Also pick up a lower hose while you are at it....labor saved.
gmcman said:
Thanks for the comments gmcman. What you are saying makes sense. I think I'm just going to get the second opinion to see what they say and not mention what the current mechanic thinks the problem is.
Part of my problem is I don't trust myself when it comes to some of these repairs . . . especially when it's on the wife's car. If it were mine I would try to do it myself but since it is her car I don't have time to mess around. She drives 30 minutes to and from work each day and takes our boys to school. I need to make sure this is done right the first time and make sure it is reliable.
P.S. Sorry for the delayed responses. I am currently working on a Pinewood Derby car with my son so I am trying to take advantage of the warm weather we are having right now.
When I moved the wifes car back in the garage I checked the fan to see if it was "running" and it was, cold engine. So can someone explain the fan operation? When the fan engages and disengages? Fan blades would be off when the clutch is disengaged? Sorry for the newbie questions but again I just want to understand.
The fan will always rotate due to residual friction. If the clutch is engaged, you won't be able to halt it with a rag. If it's disengaged, you will.
Mooseman
Moderator
If the fan sounds like a jet engine all the time, then yes, the clutch is done and it should then throw a code indicating that it is spinning faster then commanded by the PCM. But the thermostat and/or the temp sensor are still not working right no matter what is happening with the fan.
Awesome guys.
It doesn't sound like a jet engine so I agree it isn't the fan. Hopefully it's just the t-stat and/or coolant sensor. Either way I will probably have the coolant sensor replaced.
Everyone has been a big help and I really appreciate it. Thanks!
It doesn't sound like a jet engine so I agree it isn't the fan. Hopefully it's just the t-stat and/or coolant sensor. Either way I will probably have the coolant sensor replaced.
Everyone has been a big help and I really appreciate it. Thanks!
TNEnvoyXL said:
Did the repair shop provide a warranty? Might be something to ask about this time around. Only 6 months useage seems like a botched job but parts do fail prematurely.
CaptainXL said:
Sorry for the delayed response. I've been working on a Pinewood Derby car with my son.
So there's the interesting part. Yes,there is a warranty for the t-stat. However my other post on here is about the power steering pump and rack and pinion problem we recently had with the Envoy. The same shop replaced the power steering pump 3 times before they finally had to replace the power steering pump (4th time) and the rack and pinion
. They did help cut the labor cost but I'm sure they lost money having to replace that pump so many times. Based on what everyone has said here about this issue, I'm starting to feel they wanted to replace the fan clutch to "recoup" some of their cost. If they replace the t-stat under warranty, they will be losing money on me again. Anyway I am still planning to take the car somewhere else to get a second opinion and see what the other shop has to say. I'll keep you posted.Finally got my second opinion about needing to have the fan clutch replaced and the place I take the car regularly was correct. The second shop confirmed the t-stat and the fan clutch needs to be replaced. They tried to command the fan clutch off and on and it would not respond. Since the t-stat was still under warranty, I had the t-stat and coolant temp sensor replaced today (by the regular shop). Temp now is just to the left of 210 
. Now I've got to save my pennies to get the fan clutch replaced . Probably get the water pump replaced at the same time.
. Now I've got to save my pennies to get the fan clutch replaced . Probably get the water pump replaced at the same time.
floridarv
Member
- Mar 30, 2013
- 59
This is the UltraGuage vehicle monitor I purchased for another vehicle and used it to read my codes on this vehicle: UltraGauge Automotive Information Center and OBDII Scan Tool
Just a thought instead of having to run to the parts store to read and clear the codes, it also will show and give alarms for pending codes.
Just a thought instead of having to run to the parts store to read and clear the codes, it also will show and give alarms for pending codes.
Mooseman
Moderator
floridarv said:
That actually looks good. The only thing it will not show is transmission temperature. Other than that, looks cool. There is also the ELM327 and the Torque app on Android that works very well and cheaper.