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Old 29-02-2004, 09:39 AM   #1
st11x
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Coolant boiling in overflow tank

Hi members,

About 3 weekends ago, I drove my BG SP from Canberra to Kiama. When I reached Kiama, I heard low bubbling noises from the hot engine after I have turned off the ignition key. At first, I thought it was the sound of the engine cooling off (some engines make noise when they start to cool off I think ... at least my old bike did).

Then when I got back, I realised that the coolant in the reserved tank is almost dry. I had topped it up to full just before the trip!

I flushed the radiator and added a pre-mixed bottle from Valvoline. It think the top temperature is 127 degrees. During a hot evening, coupled with a traffic snarl in Canberra the same thing happened.

What I notice is that if I drive in a low gear (both times I had to use a low gear very often), the coolant in the reserve bottle will boil. Yesterday I had to drive in a low gear for quite some time looking for a car park at the Royal Canberra Show, and the temperatur guage went slightly above the middle mark. That's the first time it had cross the mark, and I just know that the coolant will be boiling. It did.

Any idea what's causing it? I suspected the fan isn't working, but when I turn the ignition key off and on again, I could hear the fan going. Are there 2 fans one of which is not the radiator fan? This couldn't be normal isn't it?

I'm a little apprehensive about taking it to Sydney and getting caught in the jam. I'm afraid it will "explode"!

Thanks
Matt
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Old 29-02-2004, 10:35 AM   #2
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I had a very similar thing happen when my water pump went. Check that the coolant is actually flowing around the system - your pump might be shot so its sitting in the one place and heat isnt being transfered.
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Old 29-02-2004, 10:47 AM   #3
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Hey! Check for any leaks!
Sounds like the overflow bottle got empty and the engine sucked in a whole lot of air!
Then pull the radiator cap of cold and top it right up, then start the car let it heat up and wait for the fans to turn on! keep topping up the coolant if it goes down! Then when the engine starts getting real hot the coolant will expand and some may come back out! Thats ok! Then when the fans turn on the coolant level drops! Quickly keep topping it up until the fans turn off! Then refit the radiator cap! Next fill the overflow bottle to about 1.5cm above the full line! Drive the car for 15 min and then turn it of and let it cool oovernight! In the morning have a look at the overflow bottle if it is below the full line, top it up to the full line! It should always be on the full line cold! This should solve that problem!

If this does not work! I would check ur thermostate and radiator cap! + Get a heat gasket check with a gadget that sits on where the radiator cap goes! It has blue die in it that changes to yellow if there is any exhaust gas in the cooling system! I have seen this a lot! hope its not that $$$$
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Old 29-02-2004, 03:21 PM   #4
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the thermostat would be one of the first things id check as its fairly common to die and is one of the easy things to check.

i think drive as little as u can, or risk damage to the engine and cooling system.
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Old 29-02-2004, 06:59 PM   #5
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Yep i have the same prob with mine. I am going to do a full flush on hte radiator and cooling system this week to test it the effectiveness of stuff called ROIL (I am going to start selling it)

by the way the second fan is for your air con!!!

got any pics of you SP ????
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Old 29-02-2004, 07:47 PM   #6
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Had a similar problem with the Cosmo, I flushed and flushed, no leaks so went and had a custom aluminium radiator made (about 3 times the cooling capacity). The thermistat had the wrong rating :evil: I could have spent $30 and 15 minutes fixing it but I thought the worst and is cost about $1k and took over two months to sort. Leason learnt was to try the simple, low cost things first.
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Old 01-03-2004, 10:42 PM   #7
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Re: Coolant boiling in overflow tank

Quote:
Originally Posted by st11x
Hi members,
Any idea what's causing it? I suspected the fan isn't working, but when I turn the ignition key off and on again, I could hear the fan going. Are there 2 fans one of which is not the radiator fan? This couldn't be normal isn't it?
your car has airconditioning yeah? one of the fans should be a dedicated aircon fan and the other will be the 'engine related' one
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Old 01-03-2004, 11:30 PM   #8
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i'm gonna ask a simple...

are you topping up the radiator at the top of the radiator, as well as the over flow??
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Old 02-03-2004, 09:33 AM   #9
st11x
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Thanks for the replies guys.

The first time it boiled over, there was nothing left in the overflow tank. I could see coolant coming dripping from beneath the car. The second time it happened (at the Canberra Show), the floor was dry and the level in the bottle did not drop.

I remembered the first time, I poured too quickly and topped up above the Full mark. I was more careful the second time. Would topping up above the full mark have caused the coolant loss? Or was the 2nd time round just lucky that it didn't have enough chance to get as hot?

The radiator fan is the one running, so that's good.

I read about releasing the air from the radiator. On Sunday, I did something to what Ezin has suggested. I opened the radiator cap, started the engine and keep it running for about 10 minutes. The level didn't go down at the top of the radiator, but it rose (I guess that's normal). The overflow tank was full to start with.

I'll probably starting checking the following in this order. Some questions:

1) How do verify that the thermostat is working? The temperature guage hovers just below the middle mark most of the time, does it mean that it's okay? I'll check the rating on my current one.

2) I'ved checked the radiator cap and it looks all right. The spring is good, it doesn't get squashed; the washer is good, no cracks and still flexible. I'll get the gadget to check the exhaust in the radiator.

3) How do you tell if the water pump is gone?


I've just take some pics, will upload them when I get home ;-)

Thanks
Matt
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Old 02-03-2004, 09:43 AM   #10
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Replace the cap anyway. It may look OK, but it can still be faulty. When I was having problems, that's the first thing my mechanic did (as it turned out, I had a hairline crack in the plastic top tank, still haven't been chanrged for having it repaired after one year!).

Caps have a pressure rating, and even though the spring may feel OK, if it's lost some of it's "spring", it won't work properly, and you'll have problems.
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Old 02-03-2004, 10:23 AM   #11
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Drop into Mazda and pickup a thermistat the cap as they should be generic and reasonably well priced. Preasurised cooling systems need the correct cap, Supercheap caps can be too generic. (Cosmo thermi cost $30 as it's for a rotary and has a hot and cold valve).

If you've got your heart set on testing the thermistat put it in a pot of water along with a cooking thermometer and boil the water.
The thermostat should be fully open at the temprature stamped on it.
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Old 02-03-2004, 11:01 AM   #12
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From what u have said! Do this!

Let the engine heat up and while doing so look for the themostate housing! then grab both the hose's going to the radiator! The one near the thermostate should be the colder one and then as the engine gets hotter they should become the same temp (Dam Hot) This means the termostate is opening (good) and u have circulation from the w/pump! (good)

If this does what i say! Take it down and get a head gasket check done! This should be free! If not very cheap $10!!

Its hard to say if its a water pump not working at full capacity! Do the pressure check and head check first to get that out of the way! Its easier and cheaper! If it comes up good! Replace the w/pump,thermostate,cap!

Please do it in the order that i have said!
Good luck!
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Old 26-03-2004, 02:17 PM   #13
st11x
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Hi guys,

Didn't have the time to work on the car till tomorrow. However, in the process, I have found this website

http://www.troubleshooters.com/tprom...210/200210.htm

and my experiences were very similar. I have reasons to believe my radiator is clogged like he described. The temperature gradient is from hot at the top, to much cooler (not cold) at the bottom. Also, the bottom hose is cold.

Last Saturday, I had to go to Sydney airport to pick up a visiting relative and came back with heater on full blast and windows opened. The journey to the airport was fine, but on the way back, the gauge kept going higher and higher until I turned the heater on. That gave me a real fright. All this while the air conditioning wasn't even switched on.

It didn't help when I met several others who had steam coming off under their bonnet along the highway, one of them was another Astina.

I'm going to replace my radiator cap, thermostat, both hoses, and reverse flush the cooling system this time, not just the radiator.

Is it okay to leave the thermostat on while reverse flushing the system? Can't find a straight answer from google.

I have the Gregory's manual, but I can't find the correct pressure rating for the radiator cap. The one on it is rated as "0.6" or "0.9", one of these two. Does anyone know the correct rating? Does your radiator cap feel easy to remove, like little or no resistance?

I went to an auto dealer who had cars with their bonnet opened. I twisted several radiator caps and found they had much more resistance than mine. It's like you can feel that it's screwing in and out.

I have bought parts from the Mazda dealer, but had been given the wrong parts before. According to them, their computer system and their manual system didn't tally! So I thought better to get feedback from the ground first.

BTW, if you are interested ;-), pictures of my Astina can be found at

http://dotphoto.com/GuestViewAlbum.asp?AID=1411981

login with username matthewsoh password matthewsoh.



Thanks for all your help.

Matthew
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Old 26-03-2004, 02:44 PM   #14
Nate
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Thats a nice car you have there - good luck with the cooling!!
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