When I was driving my Max home today after work, the temperature dial suddently shot to H level. What could be the possible problem? I checked the oil level and coolant level, they are both good.

Thanks alot.

 

thermostat. where did you check the coolant level? resevoir or the actual radiator?

 

I check it in the resevoir.

If it is thermostat, then the engine isn't really overheating, is that what you mean?

And how can I possibly check the radiator level, or to test of the ehermostat is malfunction?

Thanks again.

 

with the engine cool, uncap the radiator and check if there is fluid in there. if there is, your thermostat is most likely sticking. the only real way to "check" the thermostat it so let the car get hot and touch both the upper and lower hoses. if the temp diff is great, the thermostat is most likely not opening.

 

um... i think that is 1/2 correct. when you check your upper and low hose if there is a diffrence it can mean your t-stat isn't opening but it also could be due to lack of flow.. which means water pump.

normally both items are replaced together but normally not for use DIY-er guys.

 

I opened the radiator cap, and the radiator is dry; there is no coolant at all.

But the reservior indicates it is in medium level of coolant?

Does that mean I need a water pump, or its hose problem?

Thanks a lot.

 

well i will assume that it doesnt get below freezing in SF so, fill your rad up with water. drive the car for a day. let it cool and check to see if it drops. with pure water you will boils quicker, so if there is an external leak, you will see the steam and where it is coming from. if not steam, let the car sit for a couple of days and check your oil before driving. if there is water in your oil, you have a head gasket leak and it is leaking into the motor. the fact that your resevoir is still full makes me think the system is probably full of rust (the hoses anyhow) and that is why the res couldnt empty out. that is just a guess though, you have to inspect it to be sure.

ps.s: when you fill it up and park, throw some fresh newspaper underneath to catch and drips. even if it dries up before you come back out, you will still see where the paper was wet showing you what area the leak may be in.

 

Since it seems that the issue at hand occured so quickly at what appears lack any warning as well, it makes me think that it is not a gasket leak or a leak at all like said above...i would say start simple (other than the fluid levels) and make sure your fans are comming on...Just a suggestion. I had a similar problem as well.

 

^nah. if the radiator is dry there is a leak somewhere in the system. start by filling the radiator and inspecting for leaks, as 2da said. fill it slowly (to burp any trapped air in the rad core) and pay attention to how much fluid it takes to fill up - you may or may not be bone dry (it's hard to tell if there's coolant way down in there by looking in the top). an empty radiator will take about a gallon to fill.

now, after you fill it up - start the car with the rad cap off, and top off the radiator as the pump pulls water down. keep the cap off until the thermostat opens and spews coolant into the rad and it overflows (will take a bit of time - revving the engine helps) -- this will expel any air in the upper hose. KEEP ANY EYE ON THE TEMP GUAGE during all of this (have someone help you).

 

So I have a 1997 Maxima SE, 5 spd, 3.0L, 83K miles. About a month ago I went and got all the fluids changed, oil, transmission, coolant. I was driving on 95 from Providence to Boston and after about 30 minutes the engine overheated, lost power and I had to pull over. The temperature gauge was all the way at the top, past H. I had never seen it move past the center, so I had not been looking at it during the drive. I popped the hood and there was coolant overflowing from the reservoir and spilled on the engine compartment. I had to get the car towed.

I managed to get the car back to the place where I had the fluids changed the next day, keeping the car under 50 MPH, and the temperature dial went up a little past normal, meaning halfway, but not up into the danger zone. When I told them what had happened they said that it was probably air trapped in the radiator, so they would bleed it off. They also said the thermostat looked like it wasn't opening up so they replaced it.

I got it back from them, and didn't notice anything wrong for a couple of days, but my commute is only about 15 min. The next time I went driving a long distance, it overheated again, but I stopped before it got to the top of the scale and waited for it to cool. I brought the car back and they were confused about the problem, and decided to have someone ride with me to watch what happened and when. We discovered that the gauge only goes up when I am traveling at around 75-85 MPH, and as soon as I drop down to 60MPH it goes down again. We got back to the shop and the manager made some calls, because he thought that if it were to overheat, it would happen at lower speeds, as less air would be moving through the radiator, and thus would have less ability to cool, which made sense to me. The person he called said that it could be a bad radiator cap, because it is supposed to let pressure bleed off at high speeds so that the pump can still force coolant through, instead of having to fight high pressures. They changed it then and there, we went for another drive, and it happened again, just a little slower this time. They decided to try and flush the coolant again, thinking there might be crud in one of the lines that was preventing the full flow needed to cool the engine at high RPMs.

I got the car back, and didn't notice any problems until today, when I had the time to just get on the highway and see if I could make it happen again. It took a while, and I was traveling about 80 MPH for 30 mins, but the gauge started rising again, and went back down when I slowed to 60 MPH. The mechanic asked me to bring the car back if the problem keeps happening, or call him and let him know if it doesn't, because now he is curious because he hasn't heard of a problem where this would only happen at certain speeds.

I am going to bring the car back on Monday, and I think they will likely try changing the water pump, because it might be a little worn, but I am losing confidence that this can be fixed without taking it to a dealer. If anyone has any ideas as to what it can be that I can have them check, that would be great. I love this car, but if I can't let her drive at a decent speed, it feels like such a waste.

 

Seems like the Thermostat is shot, because what the thermostat does is when u start ur car and its cold it needs to warm up. So it blocks off coolant to the radiator until the proper temperature is reached then it allows flow through the radiator.

Most likely the T-Stat needs replacing. Another thing could be that a hose might have collapsed, look for any collapsed hoses too.

 

Either your thermostat isn't fully opening or your radiator is partially plugged.

 

While the repair shop should have done this, check in between the radiator and the air conditioning condensor that sits in front of the radiator to see if it is filled with leaves and other debris. Also have the fins of the radiator and the air conditioning condensor cleaned so air can flow freely through them.

 

Early in the process they said they replaced the thermostat because it wasn't opening. Is there a chance they put the wrong one in there, and that would cause it to work most of the time, but not be able to cope with high speeds?

A friend told me to drive the car around to get it to heat up, then put my hand all over the radiator to see if there were any spots that were hotter or colder than the rest, as that would indicate a block, but I couldn't feel any difference, though most of it was pretty cool, or more so than I would have expected. I'm hoping it's not the radiator, because I imagine that would be expensive at best.

 

The radiator seems clean to me, no big leaves or other clots, just the occasional unfortunate bug. Is the A/C condenser the pipe in front of the radiator? If so that is clean as well, no interrupted airflow. They also told me the fans are working properly, so it is not a fan issue.

 

Unlikely that the new thermostat is bad, but it is possible. A new radiator is pretty easy on that car, especially with a 5 speed - drain coolant, remove two hoses, unplug the two fans, take out two bolts, lift radiator/fans out of car. Move fans to new radiator - reverse process to reinstall.
Question: When you are running hard and temp starts to rise, can you reduce temp by turning heat and blower on high inside car?

One off the wall thought: You said you had all fluids changed, including oil and filter. Crappy oil or a defective filter could restrict oil flow, thus raising internal friction and hence temperature at high speeds. I would change oil and filter at this point.

 

Squeeze your lower radiator hose. If it feels mushy, it might be collapsing at higher RPMs (when the water pump is pulling harder), which would stop flow through the radiator.