radiator overflowing

MightyBoy tech questions and answers.
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cozza
Posts: 414
Joined: Tue Nov 09, 2010 9:57 am
Location: Boyne Island

ok well ive replaced my radiator cap because the old one was buggered, now the damn thing keep pushing all the coolant out when hot into the overflow bottle untill it starts overflowing i let it cool down put as much of the coolant in the overflow back into the radiator and top it up at least a good ltr of coolant is lost everytime, now i have replaced all my hoses, flushed the radiator and engine block and replaced the thermostat, even replaced the radiator cap again incase it was not allowing coolant to flow back into the radiator and still it does the same thing.
has anybody got any ideas as to the problem? the mechanic i took it to said the water pump was pushing water too fast for the system which is a load of crap.
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Brayden
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Location: Canberra ACT
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So the latest symptom, coupled with the overheating you mentioned in another thread suggests to me that either your engine is detonating due to a timing issue (slipped belt), or you have a blown head gasket between the combustion chamber and water jacket.
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Tez
Posts: 1176
Joined: Wed Sep 03, 2008 9:38 pm
Location: Croydon, Vic

Cozza

Been There Done That. (and more - same symptoms)
a blown head gasket between the combustion chamber and water jacket
Regrettably, this is where I'd bet my money...

Here's where mine went:
Image012b.jpg
The running engine pressurizes the cooling system and literally forces the coolant out the overflow.

Cheers
Tez
So the adventure continues...
Bear351c
Posts: 58
Joined: Sun Aug 19, 2012 7:50 pm
Location: Gawler, South Oz.

Generally, there are 2 types of rad cap, for older cars. One just vents out to the street, the other type, to an overflow bottle. The second type is a different design, that allows coolant past the rubber seal when you turn off the engine. The first style does not.

From memory, the 'small' cap is #560-90, and the 'large' cap is #534-15. Depends on the radiator you have.

If you can, start the engine with the cap off, and look into the rad, if you see any bubbles, unfortunately, that is a sure sign of head gasket/head issues.
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KEVIN
Posts: 146
Joined: Sun Apr 04, 2010 7:03 pm
Location: Melbourne South-East

I'll second TEZ on that one :(
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cozza
Posts: 414
Joined: Tue Nov 09, 2010 9:57 am
Location: Boyne Island

i tried the cap off trick and let it run for ages untill it was hot and no bubbles came through, i just dont know what is going on it happened again yesterday but the problem only seems to be an off and on problem one day i can drive it fine all day then jump in later on that day and it will overflow, the next day it just overflows all day then later on it doesnt it just seems to come and go as it pleases
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Tez
Posts: 1176
Joined: Wed Sep 03, 2008 9:38 pm
Location: Croydon, Vic

Yep...
And you'll google it, and find yourself reading other motoring forums where people have had similar problems, and you'll discover a faulty radiator cap can cause similar symptoms, so you'll trot out an buy a new cap hoping THAT's the cause (and it won't be)...

And you might even replace the radiator before you give in.

When the overflow bottle (If you've got a standard install) starts geysering out through the tiny breather hole and water-jetting the underside of your bonnet (you'll know this because you'll get rusty water flicking up from the edge of the bonnet onto the windscreen as you drive... Take the hint.

Otherwise, best of luck with it Coz.
Tez
So the adventure continues...
cozza
Posts: 414
Joined: Tue Nov 09, 2010 9:57 am
Location: Boyne Island

ok i found the prob was the head gasket must not have been hot enough when i ran it but it's definatly stuffed, will be doing the other jobs on the list for it now (cam, valves, report head). thanks guys i know ive been a pain in the backside with this issue.
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KEVIN
Posts: 146
Joined: Sun Apr 04, 2010 7:03 pm
Location: Melbourne South-East

Wise words Tez. The voice of experience :wink:
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cozza
Posts: 414
Joined: Tue Nov 09, 2010 9:57 am
Location: Boyne Island

head gasket went again but i found the cause just by one drunkin anger blast i removed the bottom radiator hose to my supprise nothing came out but it was full of coolant i gave it a shake and my god was it a mess, full of rust i wouldnt go past saying that is probably what caused the head to pop the first time it certainly was alot of rust there, so flushed the engine removed the thermostat and cleaned it all up done the gasket again and used the spare radiator must say it runs a hell of alot cooler and seems to stay at a fairly reasonable temp after a few k's sitting on 100. will keep posted on this though im not too sure if im outta the woods yet
Kuzz
Posts: 10
Joined: Sat Dec 01, 2012 4:51 pm

Hi Cozza.
I had a similar problem with my Mighty Boy overheating and found the thermostat bypass was blocked down the back of the housing, and so with the bypass blocked, the thermostat wasn't getting warm fast enough to open, and the car would boil as a result.

If you found a lot of crap in your lower radiator hose, then I'll bet your thermostat bypass is also blocked.

You might want to check it out, and clean it if it's blocked. - I used a bit of wire and poked around down the back of the housing to clean it, but had to pull the manifold off in the end, and drill mine out to clear it.

Now it works fine. No more overheating.

Best of luck with it.

Kuzz.
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