Temp Gauge on H! Help Please?

[venams03]

Hey guys. My wife just texted me a picture of the temp gauge on her way home from work. It's pegged on H!

I don't work on cars much. What are the main contributors in these things? Does the thermostat stick or go bad after awhile? I have about 120K on her so far. Just want to know what to check other than coolant level when she gets home.

[Pilgrim]

First thing for her to do is PULL OVER and find out if it's really overheated. Continuing to drive an overheated car is a good way to fry an engine. Tell her to pull over and shut it down.

If the vehicle isn't overheated, it's a sensor. if it is overheating, the thermostat is the first place to look.

A thermostat can stick on a car that's 24 hours old, but it's more typical with higher mileage. They can stick at ANY mileage.

[Warhammer]

I respectfully disagree with Pilgrim. I suggest turning on the heater full blast and leave the engine running. Make sure your AC light is on and the air is not being recirculated; i.e. air coming into the blower from the outside, while the blower motor is running. Hitting the AC button will force the electric radiator fans on. Then I would pop open the hood and let the engine compartment breathe.

Turn on your heater because the heater core can act as the radiator for your engine as it has coolant circulating through it. It's smaller and will take longer to cool your engine, but it's better than letting your engine stay hot!

While you have the hood open, you can do a quick test to see if it's a stuck thermostat. Put your hand on the top of the radiator. If it's cool or warm to the touch then you definitely have a thermostat that is stuck closed. Thermostat's are not that hard to swap out. Couple hours top on a cool engine.

[venams03]

Well she turned on the heat and arrived home. The fans were on as she pulled in the driveway. It's only 57 degrees out so right away I'm thinking it's overheated. Pulled in the garage popped hood. Cooland in reservoir OK and I think the radiator cap was pretty warm. So I'm thinking thermostat even though the coolant is about 3 years old right?

So are their links on the website to replacing the thermostat? I'm hoping I can get the part tonight so I can swap out and let her take the MO to work tomorrow. Otherwise I'm screwed for transportation

[njjoe]

I believe in the K.I.S.S. (Keep It Simple, Stupid) approach.

Car overheating? First check the coolant level in the radiator. Once the engine is cool to the touch remove the radiator cap (not the overflow tank) and look down into the radiator. Is the coolant right at the top? If not, then top off the radiator with a 50/50 mix, fire up the engine, and look for leaks. If the fluid level is fine then I would consider the thermostat.

-njjoe

[venams03]

Thanks NJJOE. I took off the cap and added little over half gallon of 50/50 mixture. Not enought so I went to the local Wal to get more.

Came home and by the time I pulled into the garage noticed that both fans were running although temp gauge looked to be normal. Weird that the fans kicked on when the heat/air was off and the outside temp is 48 degrees?

OK. So I looked under the hood for a leak but alas I can't tell since I spilled some antifreeze down the front since I couldn't get the darn plastic protector off.. DOH!

I'm guessing the fans running after a short drive in 48 degrees temps indicates it is defintely overheating right? So now I'm thinking thermostat.. Is that your assumption?

[njjoe]

If you added half a gallon of coolant and now the temperature gauge is back in the normal range I would think the overheating was due to a lack of coolant. As long as you do not have a major coolant leak you should be fine.

Did you say the reservoir had coolant in it? If so, then you may have a defective cap because the radiator should have replenished itself from the reservoir.

-njjoe

Sent from my DROIDX using AutoGuide App

[turbizzy]

In my experience with these vehicles, the thermostats almost never stick closed. I've replaced a few for sticking open and car not getting warm enough but none really for sticking closed.

With that said, the most common cause of overheating with these early Muranos is the little overflow hose that leads from the radiator to the overflow tank becomes disconnected at the radiator neck due to a lack of a factory installed clamp therefore leaking coolant. I see it all the time, check that hose! If its somewhat loose, trim a half inch off the end of the hose and reinstall it into the radiator neck's nipple.

If that hose looks good (and you mentioned the overflow tank was full) then you may have another leak somewhere else. Most other common sources of coolant leaks from these vehicles (and VQ35 engines in general) are faulty leaking radiators especially where the plastic tanks meet the aluminum radiator cores. And also the crossover water pipe from the back of both cylinder heads have a single gasket on each end of the pipe and they sometimes leak requiring replacement of the gaskets (which is slightly difficult).

My best advice, top off the coolant, hose everything down with fresh water and go drive around to get it nice and warm and dry off your sprayed water. Then park it with the hood open in your driveway and look around for any coolant leaks. If none visible, shut it off for a few hours and once its cold, remove the plastic trim and radiator cap, install a cooling system pressure tester (rent from autozone with the proper japanese adapter) and pressure test at around 18psi overnight if the leak is not easily seen. It is normal for some pressure loss to occur on the tester if the engine is still warm and not completely cold. You kinda already know its not holding pressure, your main goal is to find the leak. Pay attention to the radiator hoses and radiator tanks (remove the air intake duct so you can see under the radiator).

[Pilgrim]

Warhammer was right - the fastest workaround is to turn the heater on full blast, which increases the ability of the cooling system to get rid of heat. I forgot!!!!

I bet Turbizzy has it nailed.

[venams03]

NJ and Turbizzy. Thank you so much for the advice so far.

I let my wife drive the MO to work today after filling the radiator up last night and she texted that the gauge went back to the "H" mark after she was halfway to work (about 7 miles) so the problem is still there.

Izzy I agree. If it was low on coolant it should have pulled from the overflow which it didn't. So now that I filled the radiator, it's either leaking somewhere or the thermostat is bad. I'm not sure what else it could be. I hope to the head gasket isn't cracked? :O

I'll wait til she gets home and then check the coolant level first and add if needed. Then I'll check for leaks like you said but how the heck do you get those stupid little clips with the tiny phillips head off to get at the radiator cap. I tried last night to pry and turn with a screwdriver and it didn't budge. Then I pried again and the little F'er busted! I stopped when I broke one of them?

[venams03]

OK. She arrived home and engine is HOT!

Let it cool down and checked fluid. Added a tiny amount to radiator before it overflowed. Put cap on.

OK so nearest Nissan dealer isn't open till Monday.

So NJJOE and Turbizzy:

Should I wait and then try to use a 89 coolant change coupon which includes pressure testing etc? Or should I try to get a thermostat and change this weekend?

If thermostat is the way to go is 39 about right OEM? That's what O'reilly and Autozone quoted me.

Last question. Is there a sticky or thread that shows how to replace that puppy here? I searched and searched in every forum couldn't locate one..

Thanks in advance guys... Just a weekend warrior looking for a little help in a tough economy

[njjoe]

Again, let's keep it simple before digging in and replacing the thermostat.

Another component worth investigating is the radiator cap. A defective cap, one that does not properly seal, will not allow the cooling system to pressurize which is required to raise the boiling point of the coolant. A non-sealing cap would also prevent the radiator from replenishing itself with coolant from the reservoir.

The cap is quite a bit cheaper and much easier to replace than the thermostat.

-njjoe

[venams03]

Right NJ;

Makes sense. I did smell antifreeze but that could have been from the leftover that I spilled the previous night topping it off.

I'm going to try and find a cap this morning and will report back

[venams03]

Dangit. Picked up the cap and it was fine for about 5 miles then the temp started climbing again.

I pulled in the driveway but I can't seem to find any coolant leaking anywhere.

What should I try next?

[venams03]

Guys. I'm guessing you have to remove the plastic shroud on the bottom of car to get at the radiator drain bolt to drain coolant? The SM shows that I have to remove the water drain plug from the front of the engine. Is that necessary?

I'm guessing that I get at the thermostat bolts and hoses from the top right?