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Will a faulty radiator cap cause the coolant reserve bottle to spill coolant?

dcrou7

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So I just had a leak from my outlet pipe fixed (buggered O rings) the other day and anyway I got my mechanic to check the rest of the system for any faults and he said was all good except the radiator cap needed replacing (which I haven't got to yet) and everything was fine till I got to work this morning when I got out of the car there was a big puddle of coolant under the reserve tank. Anyone know if the faulty cap has caused it to overflow? Or could it be something else? thanks!
 

rambunctious

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Of course it could be the cause of overflow.
Get the new cap, and give them your vin number when you order because there are different caps.
 

dcrou7

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Of course it could be the cause of overflow.
Get the new cap, and give them your vin number when you order because there are different caps.

Cool thanks mate! I just haven't had time to get the new cap yet I hadn't forgotten about it. just wanted to make sure that could be the cause as I had start work and didn't have a chance to investigate properly.
 

Commo Baba

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Without the cap sealing the cooling system properly it is no longer under pressure so it will boil quicker and there goes your coolant out of the biggest available hole; overflow reservoir.

Get a cap as soon as you can or risk on overheat and busted bigger bits.
 

Wats_in_a_name

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This has happened to me. My advice would be to get a new cap asap, otherwise as Commo Baba said there could be a risk of overheat and more costly damage.
 

dcrou7

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Thanks for the help guys! Will get one asap! Also where is the best place to get one? Can you get them from supercheap or autobarn or do you have to go to Holden?
 

rambunctious

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Thanks for the help guys! Will get one asap! Also where is the best place to get one? Can you get them from supercheap or autobarn or do you have to go to Holden?

From a Holden dealer, and as I said above, with your vin number to get the correct one.
The reason I get mine from the dealer is because they are closer than the aftermarket shops and at least I know I am getting the correct part, and when you remove the old one make sure you remove all the bits left inside the housing, usually metal and rubber washer and spring, and some of the old stem.
Have a good look at the base (seat)where the rubber washer seals and clean up with something like a kitchen scourer pad if necessary as they sometimes have rubber from the old washer stuck to the seat, and this can cause the new cap to not seal correctly.
 

dcrou7

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From a Holden dealer, and as I said above, with your vin number to get the correct one.
The reason I get mine from the dealer is because they are closer than the aftermarket shops and at least I know I am getting the correct part, and when you remove the old one make sure you remove all the bits left inside the housing, usually metal and rubber washer and spring, and some of the old stem.
Have a good look at the base (seat)where the rubber washer seals and clean up with something like a kitchen scourer pad if necessary as they sometimes have rubber from the old washer stuck to the seat, and this can cause the new cap to not seal correctly.

Thanks mate. I stopped by supercheap (Holden wasn't open) on the way home from work yesterday got a non genuine one for $15 figured it's better than the one I had until I can go into Holden through the week sometime. Had it up to temp and been driving a bit and and all good so far but will definitely get a genuine one just to be safe.
 

timmy201

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It could also be that there was too much coolant in the system and the excess has come out after a heat cycle.

I used a small wire brush to clean up the threads where the cap screws on, you might get some corrosion there which prevents it screwing on properly.
 
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YES IT DOES predominantly with the later plastic O ring type.. The return valve gums up and they breath out when hot but cant breath back in as they cool so overflow bottle fills and dumps.. another sign if its bad is the top hose sucks flat when its cold again after running...
I carry a spare has happened to me 3 times now...
 
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