No Heat - Maxed out temp guage - why?

Okay people, I have a 2002 Chevrolet Prizm with almost 95K miles on it… Anyways, it’s been running great and was creating great heat until recently… Before I forget to mention it, it has had a check engine soon light on for awhile… But, I had the local FireStone check it out and do diagnostics on it and could not find anything wrong with it. Anyways, recently, I noticed the heat was no longer getting warm. I also have noticed that the temperature guage is fluctuating a ton and very quickly, as well as often maxing out pegging itself on the H, a.k.a. overheating… I am about to run down and check the coolent level, but what do you think I am looking at here as far as possible repair costs and things go? What if it needs something like a new radiator or similar? What do you think is going on here? Thanks, in advance, to anyone that gives help and/or advice and have a great day people! By the way, Merry Christmas!

I think you will find the coolant level low which probably means that you have a leak. Cost will be hard to tell without looking it over. BTW, next time you get a CEL and have the codes read, get the NUMBER that they got from the reader.

First check coolant level.

The likely case I am betting on is your thermostat is sticking(it closes when engine is cold to warm up coolant faster). Its around $100 to replace that. Do not ignore your car in this state and find a real mechanic(independant shop) to check out check engine light too. Inexpensive to fix coolant problems can destroy car engines if left ignored in a hurry.

I think you were originally dealing with a coolant leak. Now I think the coolant has run too low. Don’t continue to drive this until you get the issue resolved, as repeated overheating acn and ultimately will cause permanent and serious damage. Since you haven’t heard any knocking or ticking and the engine is still running I’m guessing that there’s been no serious damage at this point. A pressure test will find the leak, but you may get away with just a new radiator + lablor and fluid. Have the thermostat changed too for the few extra bucks.

The Firestone guy probably didn’t check the cooling system. But I’d recommend finding a different shop, a reputable independent full service garage. The Firestone guy that checked it clearly was not thorough enough and I’d have to assume wasn’t really as qualified as you needed.

CEL? Umm, stupid 22 year old never fixed a car gentleman here… Not understanding that lingo! Elaborate? Thanks for your advice regardless (I never said I would understand it, haha), and I will surely take it into mind when I have something done about the problem! Merry Christmas

I dunno if the thermostat is the only issue because, correct me if I’m wrong but, from what I understand the HVAC pulls the heat from the engine to obviously, produce warm temperatures… Now, as I mentioned before, my heat is practically non-existent but, it was good when I first bought the (used) car a few months back! I am not saying you’re wrong because, obviously, I have no clue what I am talking about but, I do have somewhat of an understanding or more of a mechanical mind that can come to understand what you’re saying quickly! I guess what I am trying to say is: your thoughts, in my mind, just don’t make sense, but that’s why I’m not the mechanic and I surely will never say one is wrong until proven so! Thanks for your help and I have it scheduled to go into a local independent repair shop at 6 tonight so, wish me luck!

Well, looking back upon the other posts/replies on here, it looks like you may be right! But, then again, you all could be wrong, but let’s be optimistic and give ya the benefit of the doubt! As far as the Firestone guys go, all I did was have them look it over about 3 days after I bought the car and do a diagnotic check to see why the Check Engine Soon light came on! I will remind you, as well as everyone, this is a Toyota mechanically with a GM interior (which is a positive, trust me!)! But, it’s all good and I appreciate your help! Heading down now to check out the coolant and everything! Wish me luck! Stupid college student here trying to do a real mans work=youtube moment for sure! Merry Christmas!

Check Engine Light. They want the exact numeric code(s) that were read out, not what the shop thought of them.

Said college student knows and reads text books. Said college student needs textbook for car called “repair manual”. Much useful information; such as checking coolant level in radiator and overflow bottle. Can said student do one thing: check the dadburn level in the radiator/overflow bottle?! That is step 1. Upon completion of step 1, will proceed to step 2. Am keeping in mind, helping said college stiudent to conserve threatened monetary resources. We fly?

I agree 110% with you hellokit.


So, I had an interview not long after I posted all that I previously had posted, earlier today! Anyways, on the way to the interview, I stopped by and bought a container of coolant… Needless to say, I added all that it would take (maybe half the container which was probably a gallon or gallon and a half) before I drove the 15 or some odd miles to get there… On the way to the interview directly after filling it with coolant, it stayed the same with the overheating engine and no heat from the HVAC. However, on the way home from the interview, it was good and was producing good heat! Even though it was acting just fine on the way home, I still put it into the shop and they’re going to do the “pressure test” and also check the temperature guage out. No, I didn’t tell them to immediately replace the temp guage because, well, it’s Christmas time and Michael here is low on cash! But, if it needs it, than I will do it! We’ll see what happens, but until then, I have one of my parents cars (which is a heckuva lot nicer than mine, but should be regardless because, they have worked hard for all they have and deserve something nice, much nicer than myself) to help me get around! Wish me luck and thanks for all your help!

Did you add the coolant to the reservoir only? If you are low on coolant you can fill the reservoir and the replaced fluid will just stay there until the engine cools and draws it into the cooling system which is why it may have worked better after the interview. Have someone open up the radiator, when the engine is cold, and make sure the coolant is up to the neck. Learn how to do this chore as it will save you a lot of trouble.

More thoughts: From the fact that no coolant was flowing through the heater core, I think the water pump was pulling air from the bottom of the radiator and not flowing any coolant at all. The fact that the temperature gauge was very erratic and would peg out implies that boiling slugs of water were making it at times to the outlet hose. So this engine was being cooled mostly by boiling off the coolant that remained in the block. The fact that the engine still runs is testamony to Toyota engineering as well as the probable cold ambient temperature.

And I think that when the car cooled down while parked (for the interview) the cooling drew some coolant into the engine…thus enabling the car to work fine and produce good heat.

I’m pleased to see he’s taking it for that pressure test.

Well, 500 bucks later and I am good to go… For now. Seemed kinda pricey for a new thermostat and a pressure check, as well as their stupid “courtesy check” which is (looking at it) a courtesy that they can skip! But, it’s cool! Thanks everyone!