Bleeding radiator questions

gslender · Postby **gslender** » Wed Dec 03, 2014 7:50 pm

Ac has nothing to do with the cooling system

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sailaholic · Postby **sailaholic** » Wed Dec 03, 2014 8:12 pm

AC will give you cooler dry air regardless of the cold/hot position.

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Roadrunner · Postby **Roadrunner** » Wed Dec 03, 2014 8:28 pm

So didn't even get as far as turning the car on his arvo.
See my other thread in this section, "have I stuffed a completely good radiator?"
:cry:

Roadrunner · Postby **Roadrunner** » Sun Dec 07, 2014 2:46 pm

Ok so yesterday got the radiator back in. Bleeding as others have suggested.
Obviously radiators are my kryptonite :frown:

Filled up the radiator. Then got a coke bottle as sailaholic suggested (one of the really thick ribbed ones) and taped it to the neck.

All seemed to go well, fluid raised and lowered and then seemed to level out, fans kicking in etc. Then im guessing the thermostat opened and a big gob of air and water came bubbling up the neck. The coke bottle instantly melted and looked like it was going to melt down into the radiator so I ripped the bottle off instantly (thankfully not burning myself)
Also got a face full of melting plastic fumes :shock:

At this time I looked across to see the overflow bottle overflowing.
The engine was still running and the coolant had settled back down, so turned the engine off and let the overflow trickle back into the rad.
Let it all cool down,put the cap on and went for a drive. All seems fine. temp slowly builds, fans kick in, temp comes back down.
Had to top up the overflow though.

Did all this 10years ago on my pulsar and never had any drama's. This has shattered me :cry:

One thing Iv learnt from all this is from now on anything to do with the engine and cooling (fluids in general) can be done by someone who knows what their doing.

sailaholic · Postby **sailaholic** » Sun Dec 07, 2014 5:59 pm

Wow! I'll have to be careful when I next try that trick! Maybe they've fooled around with the plastic in the coke bottles?

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Roadrunner · Postby **Roadrunner** » Sun Dec 07, 2014 8:37 pm

It was working brilliantly till the thermostat opened and got a face full of hot air, bubbling water and melting plastic.
A bit of liquid was coming out through the tape but nothing major. even with the hot water raising up and down inside the bottle it didn't deform.
I think it was the gush of air hot that shrinked the bottle

Roadrunner · Postby **Roadrunner** » Sun Dec 07, 2014 8:39 pm

Also should I have blocked off the outlet to the overflow bottle? Because it was completely full and overflowing when this all happened.

bruce · Postby **bruce** » Sun Dec 07, 2014 8:50 pm

All I've ever done is refill, run it, top it up and keep an eye on it. Nothing special. I think any trapped air just works its way out.

Danny · Postby **Danny** » Mon Dec 08, 2014 9:30 am

Another method would be to disconnect the rear inner hose, the one from the head, to the heater at the firewall. Add extensions to both open ends. Tape them to long stick to keep them upright so they're higher than the head. (I cut up a cheap hose from Supacheap together with a 5/8 metal coupling I had for one of the extensions and a broken broom handle to hold them.) Fill initially from the radiator cap and top up on the open extensions.

I'm currently in the process of fitting a coolant diverter so there's no hot air coming out of the heater in summer. Works well and now sorting out the vacuum control to operate it. But that's for another topic though.

green_comet · Postby **green_comet** » Tue Dec 09, 2014 9:06 am

No need to bleed the system, just fill the radiator, replace the cap and fill the overflow tank. The level will drop and it'll take what it needs from the overflow tank, you just top up the overflow tank till it's done.

Never had an issue doing it this way.

bruce · Postby **bruce** » Tue Dec 09, 2014 9:09 pm

I agree. Been doing it this way for over 20 years with no problems.

JBT · Postby **JBT** » Tue Dec 09, 2014 9:48 pm

Danny · Postby **Danny** » Tue Dec 09, 2014 10:40 pm

Some engines can have air locks especially in the head, which may or may be displaced after the first run. The MX5 head does appear to be higher than the radiator cap, where it's filled, unless the front's raised. Also our engines are unconventional with the coolant entry and exit both at the front and only the heater hose at the rear to bleed all the air out on filling.

The old VL Commodore had air lock problems but the Skyline with the same engine didn't. The Porsche 944T is another. There's even a kit for a rear tap to ensure the coolant completely fills the head and there are no air locks which, being turboed, could cause serious damage.

I'm new to playing with this car and from all reports it's probably not an issue with the MX5. Nonetheless I prefer to play safe especially if the engine is modified and/or turboed which is the case for me.

project.r.racing · Postby **project.r.racing** » Wed Dec 10, 2014 1:36 pm

It takes all of 15-30 seconds to bleed the air out of the system so why no do it. Just squeese the upper hose a few times while the car is running, and the extra pressure created moves the bubbles nicely.

Roadrunner · Postby **Roadrunner** » Fri Jul 03, 2015 7:53 pm

Just to retouch on this for anyone who finds this when searching.
I recently flushed and refilled with a weaker coolant mix for better cooling. All I did was jack the front up really high, slowly filled the radiator up to just in line with the top of the radiator core then started the engine. There was enough room in the top tank for the expanding part.
Water rose, dropped, rose again a few times, once overflowed slightly, really not much, but then dropped again.
As soon as the thermostat opened a big gulp of air came out and the level stayed solid through a few more fan cycles just to be sure.
Turned the engine off, topped it all off.
Been running nice and cool ever since.

I'd also recommend changing the thermostat while your there. They are only a few dollars and it piece of mind.