One day wife driving car home to top of our hill sees smoke coming from hood and keeps driving the extra 1.5 miles cresting to home while temp gauge in red zone.

In morning I top off with water to start diagnosis....takes 1.5 gallons to get radiator back to full. Start car and run....immediately see water flying out the broken "T" in the heater hose for burping. I've seen this before on cars with the Prestone flush T....plastic gets old and cracks over time...no biggie.

I replace hoses and put new OEM T in. Burp traditionally with raised front and funnel. Drive car and it overheats ONLY up steep hill to neighborhood (35-40MPH). Everywhere else drives fine...freeway...even freeway with large hills, stop and go traffic, etc....temp gauge stays buried in center of gauge.

Figure its the "hard to burp" G35 I've been reading about - no time to mess with so I give to my local independent. He can reproduce problem on same road up hill, tries burping again...no luck....vaccuum suck and replace...no luck....block test turns up fine. No clues. Thinks Thermostat and radiator are fine. recommends dealership.

Dealership says change thermostat otherwise its head gasket. Replace Thermostat and it doesn't fix problem. They claim its head gasket despite no symptoms. Claim that heavy load is only way to force compression chamber to push small air bubbles past gasket into coolant. Expensive $1200 test is only way to confirm. Block test and compression tests will not show it due to no load.

Does this sound plausible or are people just punting so as not to deal with a no cost lengthy debug or admit they are puzzled?

I'd rather not just dump a perfectly good car and pony up $40-60K for a new one if I don't have to. I still drive it, but only locally and take the easy road up hill to my house turning on heater to dump heat and it maybe rises 1-2 bars up the gauge before i hit the driveway.

Also...I've used bars leak on an old car before with no problems...both the brown crud and the metal flakes....in fact I still have that car with 325,000 miles on it. As a last grasp, could I try the bar's leak metal flakes or the head gasket repair stuff figuring its a tiny gap and might actually work? Or am I tempting fate and looking to brick the coolant system doing that?

Thanks

 

^^^

No year
No model
No mileage mentioned.
Have you followed the troubleshooting instructions in the CO section of the FSM for your vehicle?
Are you using the proper coolant?
Have you checked/replaced:
Water Pump?
Fans?
Clogged radiator?
Proper radiator cap?
Completed a pressure test?
Completed a compression test?

Telcoman

 

2003 Sedan V6
180,000 miles
Independent Mechanic and Dealer did the coolant replacements - so it better be proper.

Pressure Test - fine
3 different caps used (original - plus each mechanic did it again) all 3 were tested fine. I got 2 extra caps for free if anyone wants one.
Fans tested fine and come on when supposed to.

No Compression test done - read debug report above.
Radiator replaced 4yrs ago. Both mechanics didn't think that was the problem.
Water pump - original. Both mechanics didn't think that was the problem.

 

I think an original water pump on a sixteen year old vehicle with 180k miles is worth a replacement.

Telcoman

 

Thanks,

Sure the water pump could use a replacement because its old, but what would be the theory of that causing my car's problem?

Mechanics agreed that the water is flowing properly (heater blows hot, upper and lower hoses from Rad are hot.

 

I've had several cars over the years that had over heating issues, mechanics nor the dealership after replacing half the cooling system couldn't figure out. Next to my Break/Alignment shop was a Radiator shop, they had my issues figured out in minutes. Clogged radiators or thermostat that wouldn't open 100% were easy to fix, even new Thermostats s/b tested before installing them! Find a good Radiator shop in your neighborhood, cooling issues is all the do!
Gary

 

That dealership is 100% full of **** and lied to your face.

It's probably your radiator, they get old and accumulate deposits, especially if anyone in the past was using straight tap water instead of mixing distilled water with the coolant (or buying pre-mixed coolant). Deposits accumulate in the radiator fins and cause blockages, if you aren't flushing the coolant system every 30k (just a drain and fill not a power flush or anything) then those particulates stay in the coolant loop FOREVER and will cause radiator failure eventually.

Putting load on a motor does not increase combustion chamber pressure... what a load of crap. The valve closes, the piston travels up, pressure is generated and then fuel ignited at nearly the same rate every time that cylinder fires, the ECU keeps the fuel ratio as close to the same as it can, putting the motor under load does not magically create MORE pressure because the piston is still travelling the same stroke and bore on every cycle and the computer only adds so much fuel each cycle.

 

On my 130k mile '04 I had an overheating issue which turned out to not be an overheat at all - it was the $6 Coolant Temperature sensor ($6 on RockAuto, 10 minutes to install) that had failed causing the temp to read higher than it actually was. It's an cheap, easy part to replace which can show symptoms of much larger issue, so might not hurt to hand one to your mechanic if that hasn't already been tried.

If there's no oil in your coolant or coolant in your oil, and your compression tests good it's very unlikely to be a head gasket. Also, $1200 for a compression and leakdown test is crazy - they don't want your business and they're just straight up trying to rip you off. Both tests can be done in 1-2 hours by any novice mechanic with tools you can rent from AutoZone plus an air compressor for the "heavy load", and can replace the spark plugs at the same time which can be purchased cheap over the internet for the same part the dealer would install.

You'll have a good time with specialty shops like Gary's suggestion for this issue, but if there's any Japanese car tuning shops near you that work with Nissans those guys know your car inside and out and will charge a lot less than the dealership as well as taking actual pride in their work as car enthusiasts.

Cleric is probably right though (usually is), and you can get a new radiator for $50 if you buy it online and don't go to that dealership.

 

I see what you are saying but not experienced in that. More heat is generated under load however. I'll pass the dealership's explanation back to my goto mechanic and see what his response is too.

Radiator is maybe 4-5yrs old at best with maaaayyyyyybe 25,000-30,000 miles on it so I assume that would be the last possible thing to check.

I was going with the theory here that it originally overheated because of the broken burp T, and because my wife drove it after the point of redline that it caused something else to go bad. Of course perhaps that something else going bad could have cause the T to break, but seems unlikely.

 

That was a thought I passed to my mechanic and he said they monitored the temp on OBDII while going up the hill to verify that the engine temp is indeed getting hotter and its not a faulty gauge. Does seem like a no brainer to replace myself if its easy to get to.

I just replaced one on my old car after it died and went to zero a year ago....even the replacement was way off so I had to go OEM.

 

Never did a compression test...just a block test and a pressure test. Dealership isn't recommending the $1200 test...they just claim thats the only way THEY can verify it....they don't have the equipment, they send it out...and only on warranty issues where they are footing the bill. They recommend swapping engines and don't recommend that they do it. Car is worth $3500 at best from my vantage point if its fixed - zero right now. However I have no bones about paying $1000-2000 to keep it running for another year or two...but I don't want to play the dealership game of just replacing parts until I randomly fix it....IF I fix it. I want some theory to debug it first. Some of the work I cannot do at home myself. G35 engine bay is not something I have the small hands or the tools to get at things.

 

That's the thing, the sensor feeds the data to both the OBDII and the dash gauge, so don't rule that out. I'm guessing you're used to working on older cars, it must have been nice when you didn't have to drain the coolant to get the alternator out.

You said the coolant bleed valve was where the leak occurred, that sensor would have been sprayed with hot coolant and could have easily been shorted or otherwise damaged, especially given its age. I got a Beck-Arnley one which is working fine and seems to be good quality, but you do need a crowsfoot or deep socket to get the old one out. This isn't a common problem by any means but it's the last 15 year old part in your cooling system which was just exposed to traumatic events. It's had a long life and is ready to rest.

I'm curious, what happens if you stop your car on that hill and let it idle? Does it still read as overheating or does it cool down?

 

I'd first check the front of the radiator for debris, leafs, bugs, or anything that could prevent air flow. Maybe put a new radiator cap as well.

 

All those items you mentioned are in the CO section of the FSM which so many posters refuse to obtain or read.
They just keep asking the same questions over and over again
Sad!

Telcoman

 

I read the FSM in my debug and discussed with my mechanics - not the point...a simple search on this site done a month ago yields lots of different solutions or dead ends to the same problem or different situations that have already been done by me, thus the new thread to look for alternate solutions for MY situation that haven't already been done. This isn't a first blast, homework and a months worth of debug has already been done before asking for help here.

It does not overheat at idle, nor does it overheat while driving a freeway or a slight hill. It wasn't the thermostat, there are no conclusive tests showing its a HG. Most of the time it starts to rise in temperature when going up said steep hill....however from cold, it will warm up quickly (<5 min) and I can go down the hill and back up immediately 2-3x with no temp rise. However if its been running for a while in running errands or coming home from work 15-20 minutes away....it will ALWAYS temp rise going up said hill. I can slow down to perhaps 20 MPH and go up said hills with no temp rise too....but if there is traffic I certainly can't back up other cars in my tests.


The simple stuff has been done including:

Checking for debris
Hosing down rad and AC fins
Burping per "T"
Burping per raised front end
Monitoring Temps via ODBII
Checking fans operation
Thermostat change
Pressure check on cap and system
Heater runs hot
Flow checked via in/out temp hose with infrared gauge
Block test
Raised front end and ran to simulate going up a hill
Fluid change 3x (once via vacuum)
Oil drain and check and replaced
Oil check for coolant
coolant check for oil
hose changes on "T" and Thermostat
2x cap change - tested all 3 and passed with pressure test
Fan Clutch replaced.


What hasn't been done:

Water pump
Radiator
Compression check
Sensor replacements.

Looking for practical and positive help, not negative blasts about how its obvious to a solution just by doing a google search and reading a FSM. 2 mechanics including the INFINITY dealer have looked at this and punted. A 3rd trusted on also searched his subscribed database for ideas and we bounced some around with no clear direction...just random stuff.

All help is welcome by me - keep up the posts. Thank you.