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Coolant Bleeding

Eric S

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Hi Spec Z'ers,

I have a 2003 track model that I am thoroughly enjoying now that I have been able to get it on track. One thing I definitely did not enjoy while prepping it though was bleeding the coolant system! Not only did it take forever, it also made a HUGE mess. I flushed the coolant system and replaced it with water not realizing just how much of a pain in the ass it is to bleed the coolant system. I live in Colorado and my garage is neither heated nor is it insulated, so it definitely gets below 32 degrees come winter. This means I definitely need to drain the water from the system before winter freezes come, and will need to refill it in spring.

My question is: how do you guys go about making this job not suck as hard? I got one of those coolant bleeding kits form AutoZone that has the huge funnel and the extender to make it the highest point in the cooling system. While this eventually allowed me to get all of the air bubbles out, I'm not really looking forward to repeating the process.

I was watching a YouTube video of a couple guys who use one of those systems that use an air compressor to create a vacuum in the coolant system and it essentially "sucks" all the water/coolant into the system. Supposedly this prevents air bubbles from getting trapped since it draws the vacuum, but I've been fooled by claims like this before. Does anyone have one of these systems? If so, does it work as advertised?

Thanks in advance for any suggestions!

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  • 3 weeks later...
On 6/16/2021 at 7:15 PM, chinotalk said:

Hey chinotalk,

Thanks for the link. I'm familiar with how to bleed the cooling system, the problem is that the VQ35DE is notoriously difficult to fully bleed without getting air pockets in the cooling system. Also, it makes a HUGE mess. I was hoping that some fellow VQ/Z owners may have some tips on how to bleed the system effectively without making a huge mess every time.

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  • 10 months later...

Old thread, sorry, but adding my 2c...

I've burped the cooling system on my 350Z twice in the past 6mo and did not use any gadgets.

1. Jack up the front a few inches higher than the rear.

2. Open the radiator cap and put a normal funnel that fits well enough to stay upright on its own. 

3. Top off the radiator with coolant. For a new radiator I had to add 2 1/2 gals. Fill it until it's into the funnel a coupe inches.

4. Start the engine and let it warm up to operating temp with the heater on. Check the funnel. If it's empty, add coolant to keep the funnel loaded.

5. Once warmed up, rev to 3k for 20 secs. Let idle for a while. Rev again. Do this 3x while continuing to check funnel in between revs.

6. This might be optional but it's what I did: turn off engine, let it cool for an hour, then return. Not sure if this helps or not...

7. Repeat #5. Continue to keep funnel loaded with 2" of coolant while the radiator bubbles. It should not get too hot but you might put a catch pan underneath.

8. Eventually by repeating the rev/fill/idle steps a few times, you should see the temp gauge stabilize at peak operating temp (on mine it was 180*) even while revving.

9. Reinstall the radiator cap.



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