My 2003 M45 is overheating when it is hot outside (above 70 F) and why I stop for couple of minutes. Once it is hot, the engine noise increase when I drive it back and I can hear also hear the loud fan noise. The coolant level in the reserve bottle goes up from min to max level. The temperature goes back to normal once I start driving the car. I thought it could be fan clutch but it looks like 2003 M45 has hydraulic fan motor that run with oil pressure. I have tried to stop the fan with folded newspaper and Ac off and it did stop with the folded newspaper. There is no problem otherwise with heating in the winter or overheating. the problem only appears while the car is standing in a warm to hot day. Looking for advice on what to check and replace.

Check for dirt and debris between condenser and radiator. Bent fins on either.
7 years is about right for a major coolant system rebuild to restore as new performance.

Since you forgot to list your city,state, country we have zero idea what ambient is.

I live close to Detroit, Michigan so the temperature does not get high frequently. I am more concern about destroying the engine. The radiator was flushed by Suburban Novi last year ($8K miles ago). Is it normal for a fan to stop with folded newspaper at idle speed with Ac off?

I just had a very similar problem with my car. I was driving from Chicago to St. Louis and temp gauge started going crazy on my 03' M45. It almost went into the H. I had the car towed and the dealer said that it was the thermostat that caused the overheat. Also when it was overheating I pulled over and checked under the hood and the tank was completely filled to the brim with coolant. They first thought I had a blown head gasket but told me to watch the coolant level.

Did you car overheat at stop or while driving?

It was overheating while I was driving. It would stay cool while I was going down hills or on level ground. It really started heating up going up hills. The cooling fan was also running when it went above the middle line.

Put a new thermostat in before you start chasing other problems. That is the cheapest and most likely thing to fail. Everything in your post points to a bad thermostat or one that is failing.

mipinc wrote:My 2003 M45 is overheating when it is hot outside (above 70 F) and why I stop for couple of minutes. Once it is hot, the engine noise increase when I drive it back and I can hear also hear the loud fan noise. The coolant level in the reserve bottle goes up from min to max level. The temperature goes back to normal once I start driving the car. I thought it could be fan clutch but it looks like 2003 M45 has hydraulic fan motor that run with oil pressure. I have tried to stop the fan with folded newspaper and Ac off and it did stop with the folded newspaper. There is no problem otherwise with heating in the winter or overheating. the problem only appears while the car is standing in a warm to hot day. Looking for advice on what to check and replace.

Thermostats were/are designed to fail open so the heater never warms up. Failing closed or restricted has been rare on previous V8 Infiniti back to 1990. But you never know in the newer low cost designs?

True...but I have heard that one for years. Most fail open, some fail half open and some fail closed. Trust me, I have replaced them and have first hand knowledge that regardless of what they are supposed to do, they don't.

In fact a failed open can cause an overheating problem. An open one allows the coolant to cycle too fast and it does not have enough time to cool down. Never run a car with no thermostat. Its purpose is to constantly vary the speed of the coolant, either cold or hot, through the system to maintain optimal engine temp. It should close in cold weather to let the motor heat up faster. In hot weather it actually goes from full open to somewhat closed to make sure the radiator and cooling fan has enough time to get rid of the heat.

Its not just Infiniti....this applies to all thermostats in all brands of cars. If you are a Q45tech and that is just not your logon ID you should know this. Is Q45tech just a logon or are you a certified tech. Not flaming, just asking.

Q45tech wrote:Thermostats were/are designed to fail open so the heater never warms up. Failing closed or restricted has been rare on previous V8 Infiniti back to 1990. But you never know in the newer low cost designs?

I have changed the thermostat and I will drive the car tomorrow and see if it fixes the overheating problem.

Please let me know. I have a 2004 and I am very interested in the final outcome of your overheating problem.

mipinc wrote:I have changed the thermostat and I will drive the car tomorrow and see if it fixes the overheating problem.

Actually for 8+ years here Q45tech has been used for TECHNICAL not technican as I have a BS and MS in Engineering plus an MBA.
Owning and repairing [hobby] my personal 1990 Q45 for 20.4 years and spending $45,000+ on parts and labor over 326,000 miles has taught me a few things besides book learning.
Have access to 15 certified technicans [2 were at Infiniti at company launch in 1989] at our 3 different locations around ATL but too old to physically do the work any longer.

Current we have a appentice program where we employ 2 year trade school grads for a on the job training so I get a great observation in what is being turned out fresh from school with ASEE Master Certification........scarey!

Sounds like a pretty big brain trust we can all tap into. Thanks for letting me know.

Q45tech wrote:Actually for 8+ years here Q45tech has been used for TECHNICAL not technican as I have a BS and MS in Engineering plus an MBA.
Owning and repairing [hobby] my personal 1990 Q45 for 20.4 years and spending $45,000+ on parts and labor over 326,000 miles has taught me a few things besides book learning.
Have access to 15 certified technicans [2 were at Infiniti at company launch in 1989] at our 3 different locations around ATL but too old to physically do the work any longer.

Current we have a appentice program where we employ 2 year trade school grads for a on the job training so I get a great observation in what is being turned out fresh from school with ASEE Master Certification........scarey!

myother45isalesbaer wrote:Sounds like a pretty big brain trust we can all tap into. Thanks for letting me know.

Indeed, yes! Dennis (Q45tech) has been providing us detailed technical information since before the beginning of NICO - on the older Yahoo Infiniti forums, for example.

Z

mipinc wrote:I have changed the thermostat and I will drive the car tomorrow and see if it fixes the overheating problem.

I hope that was the fix! Good luck and keep us posted.

I took out the car for a test drive in 87 F temp. The car did overheat like it users when I parked it at the fast food palce but it took a little longer for the neeldle to start going toward H mark. I parked the car and kept the AC on. It took about 3 minutes till the temperature start to rise. I turned the AC off and it slow down the ascending of the needle. While standing I pushed the accelerator and kept it at 2500 rpm and the temperature needled goes back to nomral level. All indication are pointing toward the coolign fan and air flowing thorugh the radiator. As far as I know, there is no fan clutch in this model so that could be slowing down the fan when it needs to be running at a higher speed?

Running the AC just adds to the cooling load. Seems to me the coolant is not moving fast enough through the system as indicated when you say if you increase engine speed it cools back down. Maybe the poster who stated a new radiator or dirt clogging the fins was right on. I'd look at dirt in the fins first, then the water pump. Fan clutch now becomes an issue too if it has one. I thought these were electric fans....but I am going to defer to someone who knows if these are electric or have clutches.

mipinc wrote:I took out the car for a test drive in 87 F temp. The car did overheat like it users when I parked it at the fast food palce but it took a little longer for the neeldle to start going toward H mark. I parked the car and kept the AC on. It took about 3 minutes till the temperature start to rise. I turned the AC off and it slow down the ascending of the needle. While standing I pushed the accelerator and kept it at 2500 rpm and the temperature needled goes back to nomral level. All indication are pointing toward the coolign fan and air flowing thorugh the radiator. As far as I know, there is no fan clutch in this model so that could be slowing down the fan when it needs to be running at a higher speed?

Checked the coolant last night and to I was surprised to see the reservoir bottle empty? I took the bottle out and washed it many time to get the debris out of the bottom. Installed the bottle back and fill the reservoir to almost max level open the radiator cap and put a little bit coolant to top it off. I ran the can with front defroster on for about 5 minutes with radiator cap off the radiator to burp out any air in the system. The coolant level in the radiator did go down a little and I top it off by adding more coolant slowly. Now I have driven the car in 81 F and parked it for three minute and no overheating I will try it in the afternoon when it is around 90 F to see if thermostat/low coolant level/ air in cooling system were the cause of overheating. The cost so far for all these thins is about $25.

Excellent. Sounds like it could be fixed. Lets hope so. Now is the time to try to make it overheat. Idle it in Drive, AC on, anything to get it real hot in hot weather. Let us know.

mipinc wrote:Checked the coolant last night and to I was surprised to see the reservoir bottle empty? I took the bottle out and washed it many time to get the debris out of the bottom. Installed the bottle back and fill the reservoir to almost max level open the radiator cap and put a little bit coolant to top it off. I ran the can with front defroster on for about 5 minutes with radiator cap off the radiator to burp out any air in the system. The coolant level in the radiator did go down a little and I top it off by adding more coolant slowly. Now I have driven the car in 81 F and parked it for three minute and no overheating I will try it in the afternoon when it is around 90 F to see if thermostat/low coolant level/ air in cooling system were the cause of overheating. The cost so far for all these thins is about $25.

Bad news, it did overheat but after a longer interval this time. I will try to burp the coolant again and if that does not work, i am leaning toward radiator flush.

Dang, I was really hoping the thermostat was the issue. I had a thought as an old time car guy. Twice I had a temp sending unit go bad. It gave me and over heat reading. I just mention this as another alternative. Are you sure its overheating, or is just the inside gauge telling you that. The only way I know how to determine that is stick a thermometer in the radiator and see what the actual temp is.

With todays cars, I would not do that when the car is hot and the pressures build up. I would do it from a cold start, cap off. See how high it gets. Its not exactly a safe thing to do unless you know exactly what you are doing.

Perhaps another NICO guy has other ideas. Without getting my hands on the car and seeing for myself I'm kind of lost with an internet analysis. Look at the componets, there is really not too much high tech stuff that can wrong.

Just for ha, ha's I need to ask.

1. Are you running the proper coolant.
2. Does the cap pressure check out.
3. Is there white smoke coming out the exhaust.
4. Is there any scum on the radiator cap.
5. Are there bubbles coming out of the radiator.
6. Is the oil nice and clean and up to the full mark.
7. Did you pressure test the entire system.
8. Is it eating coollant.
9. Is it throwing collant out as on the ground.

Any combo of the above could be a head gasket or crack in the heads or block. Perhaps a trip to your local dealer is the best way to go at this point.

mipinc wrote:Bad news, it did overheat but after a longer interval this time. I will try to burp the coolant again and if that does not work, i am leaning toward radiator flush.

Have you checked the fluid level for the hydraulic fan?

Question....what is a hydraulic fan. I thought these were electric. Is it power by hydraulic pumps? I never heard of such a thing. Please explain. Are you just taking about a hydraulic clutch that kicks in as the heat goes up. This old dog needs and education on this one.

Reds12t wrote:Have you checked the fluid level for the hydraulic fan?

myother45isalesbaer wrote:Question....what is a hydraulic fan. I thought these were electric. Is it power by hydraulic pumps? I never heard of such a thing. Please explain. Are you just taking about a hydraulic clutch that kicks in as the heat goes up. This old dog needs and education on this one.

It is a strange set up for sure. These cars have a hydraulic pump that is built into the water pump, it drives a hydraulic motor that is attached to the fan shroud. There is also a small radiator mounted in front of the A/C condenser, you can see it through the grill. The hydraulic fluid reservoir is mounted on the drivers side cylinder head. If you take off the engine cover, you will see it, it is just the standard Nissan power steering reservoir.



It is the brown reservoir in the bottom left of the picture. I ditched that whole set up for an electric fan, much simpler!

WOW....you have got me confused how a hydraulic pump built into a water pump does anything. Are there some diagrams in detail to see how this all works. It sounds very strange to me. What does the hydraulic pump do for cooling?

I need to study the diagrams to understand what this is all about. Thanks for the info.

Reds12t wrote:

myother45isalesbaer wrote:Question....what is a hydraulic fan. I thought these were electric. Is it power by hydraulic pumps? I never heard of such a thing. Please explain. Are you just taking about a hydraulic clutch that kicks in as the heat goes up. This old dog needs and education on this one.

It is a strange set up for sure. These cars have a hydraulic pump that is built into the water pump, it drives a hydraulic motor that is attached to the fan shroud. There is also a small radiator mounted in front of the A/C condenser, you can see it through the grill. The hydraulic fluid reservoir is mounted on the drivers side cylinder head. If you take off the engine cover, you will see it, it is just the standard Nissan power steering reservoir.



It is the brown reservoir in the bottom left of the picture. I ditched that whole set up for an electric fan, much simpler!

Sorry, should have been more specific. The hydraulic pump is driven off the same pulley as the water pump, and the hydraulic pump drives the cooling fan. Here is a link to the FSM that will explain it better then I can.

http://www.nicoclub.com/FSM/M/2003/co.pdf check out page 18.

WOW!! A new one on me. Thanks for the info. I know there must have been some good reason for this, but dang if I can think of why they did this. Seems to me a space saving effort. A hydraulic fan driven motor........why?

Reds12t wrote:Sorry, should have been more specific. The hydraulic pump is driven off the same pulley as the water pump, and the hydraulic pump drives the cooling fan. Here is a link to the FSM that will explain it better then I can.

http://www.nicoclub.com/FSM/M/2003/co.pdf check out page 18.

The fluid in the hydraulic fan fluid level is at the proper level. The fan run at a high speed with AC on and at a slower speed with Ac off. I can stop the fan with folded paper which was a normal test for a failing clutch. This does not seems to have a fan clutch or I could not find one so I am not sure if the small motor on the fan is failing.
Q1. Is it normal for the cooling fan to to stop with a folded paper or something is failing?
Q2. When I took the radiator cap off and ran the car for 10 minutes to burp the air out, the temperature stayed at normal level. Could it be the radiator cap? It looked clean to me.

As I have removed my fan I can't test the folded paper trick for you, but if you find your fan is failing, i'll give you a great price on mine

I am not sure about the fan test. On the cap test its usually the other way around. Its Boyle's law. They are supposed to keep pressure on the system to keep the boiling point down. Cap off boiling point would be what is normal at your altitude.

A decent parts store usually has a cap tester and a system tester. In any case, it could be the cap and its a cheap replacement. Just make sure you get the same pressure rating on the cap. They are not all the same. Not sure if Infiniti uses different pressures on caps that will fit, but are for other models or makes.

mipinc wrote:The fluid in the hydraulic fan fluid level is at the proper level. The fan run at a high speed with AC on and at a slower speed with Ac off. I can stop the fan with folded paper which was a normal test for a failing clutch. This does not seems to have a fan clutch or I could not find one so I am not sure if the small motor on the fan is failing.
Q1. Is it normal for the cooling fan to to stop with a folded paper or something is failing?
Q2. When I took the radiator cap off and ran the car for 10 minutes to burp the air out, the temperature stayed at normal level. Could it be the radiator cap? It looked clean to me.