Major Overheating Drama Today :(

[KrazyKong]

Was driving along in the rain, car running nicely, then I look at the temp gauge and it's sitting at 90%. Holy s**t. So pulled over and stopped the engine. I could hear the radiator reservoir bubbling like crazy. I let it sit and could see there was still the correct amount of coolant in the car. So checked the oil dip stick and it looked a little low, but seeing as how the engine was hot, I think it was at the correct level too.

So let the car cool, fired it up and drove a bit more. Gauge started to rise, so pulled over and stopped again. I kept doing this for the next 20mins or so.

At this time, I turned on the heater full blast and discovered something. With the heater set to max hot temp and max (4) speed, it would cycle between blowing cold, warm then very hot air. But in conjunction with this, when it was blowing cold air, the temp gauge was rising way way up. Then all of a sudden it would start blowing very hot air and the temp gauge would lower back to it's horizontal position. Interesting. The car isn't leaking anything, no coolant missing. I'm waiting for it to cool down to check if the oil is all there.

When I started the car today and began driving, I noted how the temp gauge didn't seem to be moving at all. I gave the dash cluster a tap and it seemed to move just a little. Then very very quickly it rose all the way up to half way. It hasn't ever done that before. Normally it rises slowly and then holds steady at half way.

I put in a brand new genuine thermostat from Nissan 3-4 months back. Then a month ago I installed a FMIC. After that I noticed the temp gauge was a fleas di*k higher than before, but it was constant and never acted like today.

So is the thermostat faulty you think? or is there another problem I can look at. The car has been getting some rain on it for the past two weeks, but it's been totally fine driving it until today. So if it's an electrical problem, I wouldn't even know where to start. Could it be the water pump perhaps? or would there be other signs like leaking, squealing etc.

I hope nothing is blown or wrecked in my car. Coming up the hill to home, it was spluttering quite badly when I put my foot down, but hoping that's just the other issue I've been having with my car (started after installing FMIC and grounding the boost wire).

Edited October 10, 2010 by KrazyKong

[snozzle]

blocked heater hose ? id drop the coolant and make sure you have flow in the system and no blockages/corrosion/rust in any heater hoses / coolant lines

[KrazyKong]

blocked heater hose ? id drop the coolant and make sure you have flow in the system and no blockages/corrosion/rust in any heater hoses / coolant lines

I did a major flush 3-4 months back. Posted pics here and all. Flushed it several times, and the end result was a very happy and clean system. I've done nothing since then. I haven't even had to top up the coolant or anything as it's still a nice green colour with no residue or anything in the coolant.

If the heater hose is blocked, wouldn't that only affect the ability of the heater to work?

I just went outside now and popped the hood. The rocker covers are very hot to touch, as well as the throttle body. The top radiator hose is hot, but feels no hotter than it should. The lower one is warm and not as hot. There is still plenty of coolant in the reservoir, but haven't taken off the radiator cap yet. The car has been turned off 20mins now. It's pissing down rain, coming in sideways and going dark, so I don't know if I should do something or just let the car sit.

Edited October 10, 2010 by KrazyKong

[snozzle]

Id imagine it would cause a lack of flow of coolant in the engine and temps to rise too which is sounding alot like what you have.

Even bits of gasket goo from over appliying can break off and accumulate inside the engine and in hoses. Block off a bottleneck till a certain pressure build up, let some through then block up again.

Just a guess, could be wrong

[JonnoHR31]

park the car with the front uphill, or jack the front up, smash a cut off coke bottle in the top of the radiator and fill it up with the engine running. also crack the bleed bolt too to make sure coolant comes out. if it still does it after that check your thermostat

[r32-25t]

Good chance the radiator is blocked

[KrazyKong]

park the car with the front uphill, or jack the front up, smash a cut off coke bottle in the top of the radiator and fill it up with the engine running. also crack the bleed bolt too to make sure coolant comes out. if it still does it after that check your thermostat

I did exactly this when doing all the flushes 3-4 months ago. Bled it nicely and so far it's been perfect.

Just got off the phone with a neighbour and he recommended to start it in the morning so it'll be cold, have the radiator cap off, and look for bubbles. He said bubbles would indicate 100% of a blown head gasket?? Is this correct?

I still have my old thermostat, and could swap it out tomorrow if needed.

[snozzle]

id probably leave this to last if all else fails and your sus of the headgasket (even if its not blowing out huge amount of pressure from the radiator cap while running even tiny bubbles can give it away) you can get a co2 content tester which sits where the radiator cap should be and tells u if any co2 is getting into your coolant system from the headgasket.

Its like a blue liquid, turns green if CO2 present. Its easy to get a false positive from it so make sure you read the instructions properly.

You'll also be suprised how easy it is to miss a tiny leak too so do a pressure test also.

Im still confused about the heater hot and cold thing lol, very odd.

[KrazyKong]

id probably leave this to last if all else fails and your sus of the headgasket (even if its not blowing out huge amount of pressure from the radiator cap while running even tiny bubbles can give it away) you can get a co2 content tester which sits where the radiator cap should be and tells u if any co2 is getting into your coolant system from the headgasket.

Its like a blue liquid, turns green if CO2 present. Its easy to get a false positive from it so make sure you read the instructions properly.

You'll also be suprised how easy it is to miss a tiny leak too so do a pressure test also.

Im still confused about the heater hot and cold thing lol, very odd.

You're not the only one. If hot air was on my face, the temp gauge was horizontal and the car appeared by all accounts to be normal. When the hot air faded to cold, the temp gauge started rising upwards. I soon discovered it seemed to be going in a cycle, so I could keep driving the car knowing the hot air would soon come and the gauge would go back to normal.

I hope I didn't damage the car further or make anything worse. When I replaced the thermostat I gave my radiator quite a few flushes and also cleaned it with a water pressure blaster. If there is a blockage, I wonder why it took 3-4months+ for something to happen vs happening right away.

I'm shitting myself not knowing what is wrong, but can't do anything until tomorrow. Will do the cap/bubble test. Other than that, should I replace the thermostat and put my old one back in? and take out the radiator and try and give it another flush/blast? I hated doing it the first time, so want to avoid doing it again at all costs.

Edited October 10, 2010 by KrazyKong

[JonnoHR31]

radiator isnt your problem. you either have air in the system or you have no/minimal coolant flow which could be the thermostat or the water pump. air is the most likely culprit, hence why i said to bleed the system again.

[MBS206]

It sounds like you have an air lock in the system somewhere.

[KiwiRS4T]

Test your thermostats by suspending them in a pot and gradually adding boiling water while holding a thermometer in the water. Make sure they are closed when cold and watch when they begin to open - should be around 75deg C

[johnnyt]

bleed it properly first, have had a similar issue with my gtr after being impatient and not bleeding the system properly.

can take a while to get all the air out, so take ya time and cut coke bottle with some tape around it to seal properly is your friend.. make sure the water in the bottle is the highest point and the air will come out eventually.

[XKLABA]

have you used the heater since you flushed system, when you flush system out you have to turn heater on full to bleed or you air pocket in heater unit under the dash, keep car level when bleeding fill remove bleed bolt from engine and fill radiator till no more air is coming out of bolt hole then put bolt back in while water is coming out, if you left front of car up you will get small air pocket at front of engine as it is made so the bolt is highest point when car is level.

[DVS JEZ]

you still running a fan shroud? it seems like the thermostat might have crapped itself, as said above check its operation, if its dead then you should get a nismo thermostat,

on another note is the fan belt still on? water pump ok?

[mid life crisis]

could also be a radiatior hose thats collapsed and sucking in on it self causing a restriction

[SECURITY]

3-4 months ago he flushed it and had no problems since - im pretty sure its bled.

check your thermostat. boil water and pour it into a container big enough to hold a thermostat. throw the thermostat into it then watch if it opens up. it should open up around 3-4mm. if it doesnt then its shagged.

you dont need to take the radiator out to flush it, just disconnect the hoses and run water through it.

i read that you flushed your radiator, but did you flush your engine?

you can do it 2 ways;

1. disconnect the radiator hoses that connect to the radiator. run a high pressure water through the top hose for around 30sec. then run water through the bottom hose for 30 sec. its important you do it both ways. personally, i like to disconnect the heater hoses and flush that separately.

2. drain the water (little plug on the LHS of radiator), fill it up with water again, run the engine with a bit of revs for around 20sec (keep an eye on temps), then flush again. keep doing this till the water comes out clean.

[KrazyKong]

bleed it properly first, have had a similar issue with my gtr after being impatient and not bleeding the system properly.

can take a while to get all the air out, so take ya time and cut coke bottle with some tape around it to seal properly is your friend.. make sure the water in the bottle is the highest point and the air will come out eventually.

It was bled properly 3-4 months back. I spent quite a few hours on it, got it to where I was happy, then repeated the process just to be sure. It's been over 2500km since I bled it. I'm pretty sure air isn't the culprit at this point.

have you used the heater since you flushed system, when you flush system out you have to turn heater on full to bleed or you air pocket in heater unit under the dash, keep car level when bleeding fill remove bleed bolt from engine and fill radiator till no more air is coming out of bolt hole then put bolt back in while water is coming out, if you left front of car up you will get small air pocket at front of engine as it is made so the bolt is highest point when car is level.

Yes I've used the heater since I flushed the system many months back.

3-4 months ago he flushed it and had no problems since - im pretty sure its bled.

check your thermostat. boil water and pour it into a container big enough to hold a thermostat. throw the thermostat into it then watch if it opens up. it should open up around 3-4mm. if it doesnt then its shagged.

you dont need to take the radiator out to flush it, just disconnect the hoses and run water through it.

i read that you flushed your radiator, but did you flush your engine?

you can do it 2 ways;

1. disconnect the radiator hoses that connect to the radiator. run a high pressure water through the top hose for around 30sec. then run water through the bottom hose for 30 sec. its important you do it both ways. personally, i like to disconnect the heater hoses and flush that separately.

2. drain the water (little plug on the LHS of radiator), fill it up with water again, run the engine with a bit of revs for around 20sec (keep an eye on temps), then flush again. keep doing this till the water comes out clean.

I flushed the engine as well. Put in some flush treatment and drove 150kms with it in. I took the radiator completely out of the car and flushed it many times as well.

I appreciate the many replies here, but don't feel at this point air is the culprit. I bled the system perfectly 3-4 months back and have done over 2500kms since then. I've taken it on cruises, and driven all over the place. When I bled the system 3-4 months back I put in a brand new genuine Nissan thermostat. Maybe this is what's failed.

Just in case anyone else wants to insist this is simply an air problem, I'll repeat the critical points again. New thermostat 3-4 months ago. Full engine flush, multiple radiator flushes with the radiator out of the car. Car faced uphill with the cutoff plastic bottle method and bled all the air out. New coolant and top ups to get the levels right. 250kms since then, and not one problem until today.

The car has been running so good on fluids I haven't even had to touch the coolant or the oil. Checking the coolant today when it was overheating, the resovoir was bubbling like crazy, but still had the correct amount of fluid there.

If it's not stormy tomorrow, then I'll be able to take off the radiator cap and see how the fluid is. As well as checking the oil dipstick. Then I'll start the car, with cap off and see if any bubbles are there. If no bubbles, the next phase would be to take out the thermostat and check it in boiling water. Other things I could do are take radiator out and flush it again myself, or take to a radiator place that does a flush.

Other than that, I can check the water pump, but wouldn't know if it was working or not. Is there a method to check this?

[DVS JEZ]

A quick way to check the water pump is when the radiator cap is off and engine runnin u should be able to see water flowing BUT if ur thermostat is closed and or stays stuck closed then u wont see this. Better off pulling the thermostat out 1st and testing it. U can ever try using the car without a thermostat if u cant get one. But if u use it on the freeway u might have issue with it getting hot cause the wTer flows too fast throughthe radiator to get cooled down enough

[KrazyKong]

Well well, the plot thickens. With dread I popped the hood and took off the radiator cap and found to my horror it was empty. Seeing as how it was hot yesterday, I gauged that it still had coolant because the reservoir bottle was full. So I fill it up with tank water, and let it idle with the cap on. Soon enough, the green coolant showed up that must have been in the block or behind the thermostat. Feeling more bold I took it for a drive and found the car run fine. I had the heater on full blast to see if it would do it's cycle thing, and once I was up to temperature it seemed to constantly blow hot air. But I did note, though am not entirely sure, that when I came to a stop and just idled for a bit, the air then starter getting colder. It wasn't until I was driving again that it got back to hot.

I've shut the car off and letting it sit for a bit. Then will park it uphill, and will fillup/bleed the system with the cutoff bottle.

I have no idea what's going on, but the radiator part this morning seemed completely empty. Either I got a leak, or something more sinister, or mysteriously the coolant just vanished one day.

My oil is clean, and I didn't notice any bubbles coming out of the radiator. But since it was empty, I won't know for sure until I bleed properly.

Still very much worried, but at least it started today and drove ok.