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Temperature gauge problem


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eqwlyz
New User

May 25, 2016, 6:15 PM

Post #1 of 10 (835 views)
Temperature gauge problem Sign In

Hi every one, I have recently done a radiator flush & refill on my 1989 Toyota corolla GLX. Engine: 4a F.
After I have done this my temperature gauge isn't working properly, It stays on C (Cold), And it will stay on this after a good hour of driving, But as soon as I stop for a few minutes it starts rising, So I've determined that it only rises when the car is sat still, But it also started dropping back down again as I started driving.. Also when it rises it doesn't quite hit the 'half way' spot it should be sitting at. I have checked my radiator hoses after driving for a hour or two and they are both as hot as each other so im assuming the thermostat is working?

Any help will be much appreciated thank you, Michael.


Tom Greenleaf
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May 25, 2016, 8:31 PM

Post #2 of 10 (823 views)
Re: Temperature gauge problem Sign In

? Michael: This just happened when you flushed and changed coolant and now this? Did you remove the thermostat to flush it out as you almost have to for a good flush?


If so thermostat may not be in place properly allowing flow all the time if even partial would run cold or erratic which it seems to be doing.


This really does point to a thermostat that's not correct, stuck part open maybe even with debris if this really was a clogged cooling system isn't right and bet the gauge is.


Same temps of hoses in and out of a radiator alone suggests it isn't transferring heat normally. For now it DOES suggest a problem with the thermostat by your description,


T



eqwlyz
New User

May 25, 2016, 9:33 PM

Post #3 of 10 (818 views)
Re: Temperature gauge problem Sign In

Hi thanks for your reply, but no i didn't remove the thermostat during the radiator flush as the tutorial i used didn't say to do it :\

Should i just replace the thermostat?


Tom Greenleaf
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May 25, 2016, 9:57 PM

Post #4 of 10 (815 views)
Re: Temperature gauge problem Sign In

OK - Then essentially you only changed the coolant not a real flush at all. That's fine if the objective is to just get new coolant in and the old replaced but if it needed flushing (some really don't no matter how old) I question junk moved and is causing a problem you didn't have.


You can check operation of a thermostat with a touchless infrared thermometer and know it's doing what it should, when it should.


Without that bet you can feel upper radiator hose get slightly warm way too early when the idea is for it to seal shut till engine internal temps require some or a lot of cooling which will vary by ambient temps, type of driving such as just stop and go or steadily moving along.
Need to know real temps and where. If running as cool as radiator can do all the time it's not good for the engine, fuel use or emissions. Also may not run well.


You may have and probably do have air in the system confuses both thermostat and temp senders. You can tell if properly filled somewhat if heater works properly even when not needed should blow warm/hot air thru floor vents. If running that when temp reads "normal" and goes to cold it's not right. You may find it doesn't blow warm air at all if air is in with coolant.


More to the whole thing than you may think. Antifreeze protection level should be a 50/50 mix hard to do unless system is totally empty of flush water as all water doesn't come out. If too strong it can't cool properly. If way too weak it adds to ongoing corrosion inside.


I would test with the thermometer as mentioned that temps are a proven temp not a guess and rule out a faulty gauge.


In short it should never read cold even in frigid weather as thermostat doesn't allow that as it should shut tight and doesn't for whatever reason so just cools as much as it can all the time. Do real checks for that not guesses on the temps, know what they really are,


T



eqwlyz
New User

May 25, 2016, 10:14 PM

Post #5 of 10 (813 views)
Re: Temperature gauge problem Sign In

The heater works fine & correctly, there is no noticeable over heating after an hour of driving. I flushed the system with distilled water until it flowed clear (had motor running with cap off to circulate it while draining?) . I did the mix at 60/40(hopefully) as toyota reccomends above 50 & below 70. I may have gotten air in the system though as the coolant went frothy but it doesn't froth now its nice and green. Should i just replace the thermostat?


Tom Greenleaf
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May 26, 2016, 2:39 AM

Post #6 of 10 (806 views)
Re: Temperature gauge problem Sign In

Quote">>Should i just replace the thermostat?<<"
In this case I'd say yes. Again you can't flush out with it shut tight in place so decide if you need to drain this to filter new coolant for re-use if you really can but do measure coolant protection after it mixes itself with many cycles.


Distilled water for flushing? How did you do that and why? That's waste water and the idea is some force like hose water which would be drained again before the fill. I do suggest distilled for the final mix not knowing what every water otherwise used would contain universally.
Some very minor air in a system is about inevitable and would purge itself out. Not all will purge out large amounts or refill well or possible without machines to help.


Yes - some suggestions will deviate for an industry standard of 50/50 mix but must have some.


Hard to say but with thermostat in and flushed like that you really didn't achieve much except some new coolant IMO. So yes new one and look hard at old one to see if it's caught some junk or what.


This routine service seems so simple but many are a real pest to do and get just right,


T



eqwlyz
New User

May 26, 2016, 3:09 AM

Post #7 of 10 (803 views)
Re: Temperature gauge problem Sign In

I followed a video tutorial online. I think it will be best if i just do another flush & refill but this time replace the thermostat. Would you be able to tell me the correct way to do this or refer me to a good tutorial? Do i just take the thermostat out and run the motor with a garden hose in the radiator with the drain plug open or somthing? The method i used previously required me to empty the radiator, then run the motor "to get the rest out of the engine block into the radiator to drain it too" but that's where im confused with the thermostat.. then i had to put fresh water in with a flushing liquid and run the motor for 20 minutes and then drain it again and fill with coolant and water mix. But by the sounds of it i wasn't draining it correctly.. i think it's possible the issue is a build up of crap due to me not flushing it properly.


Tom Greenleaf
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May 26, 2016, 3:39 AM

Post #8 of 10 (800 views)
Re: Temperature gauge problem Sign In

Oh boy: Ya - these on line "tutorials" would have folks think all things are the same and just do it this way and full of crap many times.


You can't leave a plug (thermostat) in as it would stay shut tight so ZERO flow while flushing - near pointless! These things on line will NOT mention that you also may need to drain the engine block with bolts or plugs in the water jackets NEVER discussed and sediment collects there that even flushing doesn't get.


Think of engines not used just in cars all over the place. RV, Marine, Back up power sources that sit for long times and in use unseen for public things like water supply, public sewer even for underpasses that flood out we just don't think about. Not usually a Toyota but sure could be the same blocks.


I know antifreeze is a bit pricey but would start over with better understanding. You do force water forwards and backwards thru engine, heater core, radiator till clean then drain and fill, bleeding out air as each type requires.


In short it's not as plain 1,2,3, as it seems. Gets worse too as antifreeze is a real poison and hazmat almost impossible for DIYer to control and dispose of waste product properly! Quite simply - most just don't and ignore all that.
Actually you are lucky it's an older Toyota probably far less hassles then some other types out there,


Tom



Discretesignals
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May 26, 2016, 4:42 AM

Post #9 of 10 (795 views)
Re: Temperature gauge problem Sign In

I've seen gauge senders go bad after coolant services. Check to be sure the temperature gauge sender connector isn't all corroded. You can also use a IR thermometer to measure the temperature at the gauge sender to see if it is reading correctly.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Tom Greenleaf
Ultimate Carjunky / Moderator
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May 26, 2016, 5:03 AM

Post #10 of 10 (792 views)
Re: Temperature gauge problem Sign In

All true DS. I wont use chemical flush and in fact do NOT do it at my place but rather a place that has a catch area for hazmats. This is an '89 so lots of things could be weak - sender and the plug to it or who knows?


OP check on a real IR thermos. They range from $10 bucks on up. If you point one right at a thermostat housing you can tell when warmed up it should really read the rating of the thermostat. All I've checked do. If you are about to get into lots of guessing and wasting time it's totally worth it for good info,


T







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