zprz

Hey guys,

Got a bit of a problem here. My 2003 Z recently overheated real bad and the radiator cracked. I took it to a local garage and he changed the radiator. Then he ran the car a bit and it still overheated, so he changed the thermostat. Then he drove it around and it was fine. So he gave it back to me, and I drove it for about 2 weeks with no issues. Then one day it overheated on me, probably when I gave it a little kick off the freeway exit ramp (after driving for 2 hours with no issue). I caught it kinda early, so I sat it out about an hour, topped off the coolant, and took her to the mechanic. Told him what happened, he checked both the hoses (upper and lower), and they seemed hot, so he determined probably the thermostat is fine. He let the car sit for 1 or 2 hours and it didn't overheat, so he concluded its most likely a blown head gasket.

I was able to drive it home with no issue. Then a few more times, I let it run for some time, 10-20 minutes, no overheating. I drive it a few hundred meters and it heats up.

I did some searching on these boards for similar issue and it seems 350zs have a common problem of getting air trapped in the coolant system. So per this forums advice, I topped off the radiator with water (they're both actually already mostly full and don't seem to be leaking), turned it on, and waited for it to overheat. Now, it actually doesn't usually overheat when I idle (only when I drive), but when I turned the heater on (which doesn't work), after a few mins I heard the fans crank louder and it overheated pretty quickly. I turned off the engine and popped the relief cap for a few seconds. I repeated this 4 or 5 times but it continues to overheat.

Is this a blown head gasket? Does the fact that my cabin heat not work have anything to do with it? What should I do next?

Thanks a lot.

MicVelo

The only thing your "throw parts at it and see what sticks" mechanic didn't put on was a pump.

zprz

So are you suggesting I should get a new water pump?

Some additional info that I'm not sure is related:
- Fans work
- A/C very cold, but no cabin heat (continues blowing cold air)
- 128k miles
- No smoke that I've noticed

hulkout

First of all, never go back to that mechanic again. Sounds like he's taken you for hundreds by throwing parts it didn't need at it at this point and has not fixed the issue. That's my experience with mechanics though. I don't trust them. You're lucky he didn't break more stuff just to keep you coming back. But I won't get into that...

Do you have coolant in your oil or vice versa? That's a good sign of a blown head gasket.

dcains

iTrader: (15)

Same rhread, different day. No one looks at the FSM or uses the search function (or even Google), do they?

Find the thread called "coolant purge nightmare", buy the funnel, follow the instructions to the letter.

i8acobra

iTrader: (6)

If the heat doesn't work, there's air trapped in your heater core. Search and you'll find the answer. You need the funnel and either ramps or a jack with two jack stands.

zprz

I generally share similar sentiments regarding mechanics, but this one in particular has been helping my friends family for many years and seems to be doing OK by me. Don't think he is a 350z expert though... I actually originally took my car to Nissan service, and had it towed FROM their service center to this guys shop (ultimate slap in the face to them). But they had already determined that my radiator was cracked so I just asked this guy to replace it. And the theromstat he did do himself and only charged me for the part and not the labor (labor on the radiator), was together less than half of what the stealership wanted for only the radiator (including how much I paid for tow).

I will check if anythings mixing, thanks.

As I mentioned in my post I am well aware of this issue with Zs and have spent several days looking it up on this forum as well as other Google resources. I am not a mechanic and figured a few more opinions couldn't hurt. Every problem could be different. For example my cabin heat also doesn't work, and in several threads I've read here, it is suggested that it can mean head gasket. (Although usually it is still air bubble, I understand that. I tried bleeding it out all weekend with no success before I posted this thread ). I will look at that thread and keep trying to bleed since it is so common. Thank you

Will look into it, thank you. Appreciate everybody's advice.

PP08HR

iTrader: (2)

If his radiator was cracked then it most certainly would need to be replaced.

Sounds like you ran your 1st overheating issue too long and did possibly cause headgasket failure.

If you bleed the crap out of it and it still overheats then do block test... If fact ask the mechanic to do a block test anyways.

zprz

My first one, you mean which cracked the radiator? The way that happened was: I had just finished driving, and as I shut off my ignition, it popped quite loud, steam poured out and coolant was all over the ground. Again, this was while I was parked and turning my car off. After that happened I did not drive it at all, and got it towed until the radiator and thermostat were replaced.

I will try a block test.

Today my coolant levels in the overflow bin are much lower than yesterday. Also, my RPMs are not always stable on idle, they sometimes bounce between about 700-1300. And I just noticed the radiator cap is not stock, but rated at 13lbs.

zprz

Yesterday when I was bleeding my cooling system, I was able to drive around fine for around 20 minutes, high revs and all. Then when I turned my car off, waited about 30 minutes to have lunch, and back on, it overheated after driving just a couple hundred feet. Then when I waited again and turned it back on, it would overheat as soon as I turned my heater on (which didn't work) or drive. Barely inched it back home.

Today, after topping off the radiator and reservoir as it was quite low, I bled it again and it did not overheat. I was again able to drive it all morning. I drove it around for close to an hour, did errands across the city, all without turning my car off, just kept it running inside while I ran around. What's funny is my cabin heat starts working as soon as I start driving. It gets really hot when I'm driving fast but as soon as I slow down (even red light), it becomes cold again. What could this mean?

I'm going to do a block test later today and will report back.

zakmartin

In all probability, the heater core issue means you have air in your system that needs to be bled out. Read the FSM radiator flush section and do what it tells you to do. At the very least, buy a Lisle coolant funnel or if you have a compressor, get a UView airlift kit to properly flush your radiator. If you don't feel confident enough to do this very simple task, as it's been covered in countless threads on this board, then take it to a qualified shop. There really isn't much to this, and if you're having this much of a problem bleeding your system, then maybe that's your best course of action to leave it to a pro.

To be honest, your first "mechanic" (the guy who changed out your radiator) should be on the hook for bleeding your cooling system correctly, and if he isn't up to doing it right, then he should pay someone else to do it for him. Either way, I'd be pretty pissed at him at this point, family friend or not.

dcains

iTrader: (15)

Unless you're using the right tools and following the proper procedure, you're wasting your time and may be causing damage. Why is this so hard to understand?

APTech

If you let the car idle for an hour and it didn't overheat, there's no way its a blown head gasket, but hell at this point just do a compression test if you think you're capable of it.

hulkout

If the heat works when driving but not when stopped doesnt that point to a water pump issue?

dcains

iTrader: (15)

No. There's air in the system. Let's beat this dead horse some more.

zprz

Thank you very much. I will go back and ask him to bleed the system better.

I rented a block tester and went to use it today. I took the radiator cap off, made sure levels were adequately low, and turned the engine on. After getting to idle temps and waiting a few minutes, it started leaking out of the radiator cap. I figured there might still be too much coolant so I let it trickle out for a few more seconds, then it started to spew more and more violently so I turned it off (even though the car was not overheating past idle temp).

I waited about an hour, siphoned more, and tried again, same result. I obviously can't do the block test under these conditions. Does this still point to air in the system or could this mean something else?

Look, I understand its likely there is air in my cooling system. I mentioned the high likelihood of this in my first post. It's just I want to check it myself if I am capable before going to a mechanic and telling him he's wrong based on something I read online without any checking myself. Block test seemed easy enough so I tried it.

Thanks for everybody's invaluable input.

dcains

iTrader: (15)

This is my final attempt to help someone who clearly isn't paying attention.

Buy the funnel or you'll never get it filled. The funnel allows the bubbles to come out of the coolant cap, and then also lets the fluid forced out by the bubbles to flow back in.

RWDBajan

Can't anyone test for either combustion gases in the coolant or coolant in the exhaust? If neither, it's not a head gasket. VQ engines seem to be pretty strong though. From experience with a VQ25 which had a mechanical fan. The fan bracket broke, which led to the fan stuffing itself through the radiator. I drove it home with no coolant (2 miles). Replaced the radiator and fan and it was all good.






They are beasts to properly bleed air out of though. I had to make a tall funnel from a 2 litre soda bottle, and just keep bleeding the system. I seem to recall I had to break the heater hoses to get the air out.

zprz

Great. Will do that, thank you very much. I misunderstood about the funnel but it's on the way from Amazon now. Sorry for the confusion, really trying to pay attention, just this is my practically first time under the hood (of any car), so I'm still learning.

Thanks, I already replaced the radiator and the fans seem fine so I probably still have air in my system so I will try the infamous funnel. I'm a little concerned about all the spewing coolant when I leave it open but hopefully with the funnel attached it will draw the air out and coolant back in, as stated. I'll still be extra careful about doing it.

Thanks again! I'll report back how it goes later this week when my funnel comes in.

zprz

I got my funnel today and followed the procedure. It attached well and seemed to get a lot of bubbles out. But after a while of running at idle temps, it would start to bubble severely and overflow the funnel forcing me to kill the engine. I did this repeatedly for almost an hour, with it overflowing each time after a few minutes. I had the relief cap open as per the instructions.

So then I decided to see if despite the overflowing it helped any, so I took it for a drive around the block, no overheating. Then I waited a couple hours and went again, no overheating. Then I waited a few more hours and went again and this time it overheated on me pretty bad again. And my cabin heat still doesn't work. After waiting half an hour after overheating, I started it back up at idle temps and after about a mile of driving it overheated again.

Does this mean it's something else or did I do it wrong? Please advise. Thank you.