erratic temp guage

[userfriendly]

Guy opinons pls. My temp guage has been going up and down. Yesterday, it was normal just above 1/4 while driving at speed sa SLEX. Upon hitting bumper to bumper traffic at Alabang flyover, it went to a shade below 1/2. It stayed there for a while. Went down again when I was able to speed up. Up again in traffic.

Upon reaching Merlco Ave, it was almost 1/2 (stop and go traffic). Stop at the traffic light there, went down again to above 1/4. This kept repeating until I got home. So basically its cool when the road is clear but creeps up during traffic.

About a month ago, I had the car serviced at the dealer for overheating problems. They fixed a loose wire. Also, my thermoswitch is new. Coolant (prestone premixed) level is ok, serpentine belt looks fine and does not seem to be loose.

Can this be a sign of something wrong or am I just being paranoid?

[roninblade]

baka di totally fixed yung loose wire.
ganyan din kasi problema ko... maluwag lang yung connection sa thermostat.

[4JGtootsie]

I think its normal. Your temp sensor is doing its job. From a fast stint to a bumber to bumber the water pump slows down circulation which in effect lessens its ability dessipate heat in the radiator fins to the air by virtue of convection.

When you stop an engine there is such thing as afterboil because the pump stops circulating even if the engine is still hot. Somewhat this explain the reading in your gauge.

[userfriendly]

I think its normal. Your temp sensor is doing its job. From a fast stint to a bumber to bumber the water pump slows down circulation which in effect lessens its ability dessipate heat in the radiator fins to the air by virtue of convection.

When you stop an engine there is such thing as afterboil because the pump stops circulating even if the engine is still hot. Somewhat this explain the reading in your gauge.

Pls clarify di ko naget yung "When you stop an engine there is such thing as afterboil because the pump stops circulating even if the engine is still hot"
The engine is still idling so dapat naikot pa rin yung pump diba? Although at a slower rate.

Also, how fast should the temp guage react? I was in Dona Hemady yesterday (part of the same trip as the 1st post) beside the old Magnolia factory temp was near 1/2. Upon reaching the corner of 8th street and Hemady, guage has already gone down.

Last Tues, temp went up to just a shade above 1/2. I pulled over and poped the hood, everything checked out ok and the temp returned to normal. Did not think much of it at the time. Related kaya ito?

[4JGtootsie]

Afterboil occurs when you turn off the engine(no idle). I was trying to explain fast, slow, no circulation of the water pump in relation to temp. I am sorry for the confusion.

Let me try to diagnose further?

Before you serviced your car for overheating how high did your gauge reach? Did the engine shut down because of overheating?

[userfriendly]

Afterboil occurs when you turn off the engine(no idle). I was trying to explain fast, slow, no circulation of the water pump in relation to temp. I am sorry for the confusion.

Let me try to diagnose further?

Before you serviced your car for overheating how high did your gauge reach? Did the engine shut down because of overheating?

The guage almost reached 3/4 but was not yet in the red zone. Did not shut down the engine. What I did was bring it to a gas station, by this time it was already going down but still above 1/2. They poured water on the front of the radiator infront of the fans, engine idling. Metal part with the fins, not the plastic top. Temp immediately went to normal and was able to drive home normally.

BTW, the stealership said the wire that they soldered was loosening when it heated up and prevented the fans from turning. Thing is, I distinctly remember the fans turning at high speed in the gas station. Could it be that its the low speed that wasn't working? Anyway, after they fixed it, all was well for about a month.

[4JGtootsie]

When was the last time you checked the coolant level?
May bawas ba?

[userfriendly]

This reminds me, before having it serviced (may 2 pala), the driver needed to add coolant about once or twice a month. I replaced the rad cap and had it pressure tested (last week of April), no leaks naman. About 2 weeks ago, nagdagdag yung driver namin. Did not see how much he added.

[4JGtootsie]

I think you have a minute leak either in the clamps or the minor water tubes. Since you have added coolant additive, its color will show you the leak. maliit lang pero water escapes in the form of steam.

[userfriendly]

Yun din ang inisip ko dati, kaya nagpapressure test ako. Hindi bumaba yung pressure sa guage during the test. Wala rin akong nakikitang discoloration sa clamps or hoses.

[finchy18]

I think its normal bro kpag traffic maging half temp sya at kpag long drive syempre baba ng 1/4. or kung hindi yan ganyan dati well its not normal.. check the radiator cap and aux fan..
sir what car model and year?

[4JGtootsie]

Check it pag 3/4 ang temp sisingaw yan somewhere.You will hear it.
Pag wala pa rin, its possible na sa cyl. gasket. Wag naman sana.
Do you have an overflow reserviour? May boiling ba doon?

[userfriendly]

I think its normal bro kpag traffic maging half temp sya at kpag long drive syempre baba ng 1/4. or kung hindi yan ganyan dati well its not normal.. check the radiator cap and aux fan..
sir what car model and year?

Chevy Venture 2002 model. Installed original rad cap last week of April. Before this, temp did not go up and down. Defective kaya yung new rad cap? O defective yung old cap kaya di gumagalaw yung reading?

Check it pag 3/4 ang temp sisingaw yan somewhere.You will hear it.
Pag wala pa rin, its possible na sa cyl. gasket. Wag naman sana.
Do you have an overflow reserviour? May boiling ba doon?

Wag naman sana. Pero aside from the coolant loss, I dont see the usual sins of defective cyl head gasket. No white colored smoke, no oil discoloration, no oil in the coolant, no power loss.

The time it almost reached 3/4, I was not able to check the reserviour. If there is boiling, what does it indicate?

What are the symptoms of a clogged radiator? I don't use the manufacturers recommended Dexcool coolant. Read too many horror stories of it turning into gel and cloging the rad. May effect kaya ito?

Also, I can borrow a laser thermometer from work. If I measure the entering coolant temp and leaving coolant temp, how big a temp difference should I be looking at? May use ba to?

[Yoda]

Is your thermostat working properly? Maybe it's stuck in the open position, or removed.

Kapag umaandar ka, water flows faster because the pump is driven faster. There's also a greater airflow through the radiator. If your thermostat is working, then it would regulate the water flow such that the engine operating temperature is maintained.

[4JGtootsie]

A loud boiling/gargling sound is a sign cyl head gasket failure. You can confirm it by the smell of exhaust fumes coming out of the reserviour.

[userfriendly]

Tried to troubleshoot. Car has not run for almost 2 days. Checked both upper and lower rad hose. No sign of damage and both dry. Checked reserviour, looks full. Removed the hose leading to the reserviour. Removed the rad cap, coolant spilled out. I noticed that with this car, whenever I remove the rad cap, coolant will spill out. What does this indicate? Overfilled kaya? Incidentally, the rad cap is at an angle. almost 45 degrees.

Started the car while looking at the exhuast pipe, no white smoke. Went to the back, no visible smoke at all. Just some water going out of the tail pipe. I belive this is normal.

Looked down the rad cap hole, coolant looks clear, no discoloration and no signs of oil contamination. Held the upper rad hose until I felt it warm up. Not long after coolant in rad hole went down a bit, looks like its circulating. No bubbles in coolant. (I belive bubbles is another sign of cyl gasket failure or air in the system) However, lower rad hose took longer to heat up.

Used an inexpensive hydrometer from Concorde. Result was good coolant, 225F boiling point protection. Not sure how accurate cause I was able to get the same reading with pure water.

Turned on the AC. Both fans turned on. Turned off AC, fan still running. Used my finger to touch a small part of the rad not covered by the fan, near rad hole. Area was hot. Did the same to the side of the upper rad hose. Also hot. Could not test the lower part for safety reasons.

Went to the back and smelled the exhuast. Smells normal, no smell of oil or coolant.

[4JGtootsie]

I think every thing is in order.
Two more questions. When was the last time you serviced/cleaned your radiator? Thorough flush?

[userfriendly]

Di pa na service or flushed. I'm thinking that it might be dirty. At speed, the air flow is enough to keep it cool. At traffic, without the airflow, the temp goes up.

How do you check if a rad is dirty? I'll borrow the laser thermometer from work and if there are any cool spots then it is dirty. Is this correct?

The guage used to be relatively steady it will take time before it goes up or down. Now it reacts even with short distances.

[4JGtootsie]

There is no sure way to know. Since never pa nalinis yan I guess it is time.
Since QC area ka naman yata. Sa tabi ng Ellens near Morato cor Timog may magaling na radiator shop.

[userfriendly]

I'm thinking that it might be bec of:
1. stuck open or partially open thermostat
2. clogged or dirty radiator
3. fans are not spinning at correct speed

Which is most likely? And how can you tell if the fans is spinning at the correct speed? I see it spinning and can feel the air but have no idea how strong it should be. This car has 2 speed settings, low fan and high fan.

I also called 2 dealerships and explained the prob. The 1st said that as long as the guage does not go to 3/4 I'm ok. Normal lang daw. The 2nd dealer said bring it in cause it might lead to overheating. Sino kaya ang tama?