Duff rad cap?

[easty-5]

As some may know, I have been having overheating issues for a while now. It only ever overheats on long mtorway journeys. There are no visible leaks that I can see. My coolant level hasn't budged a bit in the past 2 weeks.

I just checked my Rad cap. I took off the 6mm hose that goes to the expansion tank and let the engine get up to normal running temperature. Once up at temp coolant was dripping out of the little nipple where the 6mm hose is usually connected. Once I revved the car then it came shooting out.

Also, when I was at knockhill a few weeks ago, once the car had been out and got up to temp, it started dropping its coolant. To me it seems as if when I put my foot down, it is throwing the coolant into the expansion bottle, which is overflowing, hence me losing coolant, once it starts to cool it is trying to draw the coolant back in, but if there is no coolant there then it will just be sucking in air, adding another reason for it to overheat. Does that sound right or am I way off?

Do I need a new rad cap?

[JJ]

Firstly, these coolant systems are crap to gauge if its low on level....

What you'll probably find is its probably not lost any on the filler neck, but the rad is partly empty... crap I know... so when you check, do a good few bleeding exercises first....

ie. Cap off... goto the front and bleed off the radiator... coolant level should drop...

Tell tale signs of engine integrity problems, is carry out all the bleeding correctly first, leave the heater pointing to hot and take it for an inspired drive.. the early signs of overheating is the heater will go cold.. when it does this, it means there is no coolant circulating around the block... so get ready to ditch the car on the side of the road....

Then its a process of elemination ....

Check the caps seating, the rad cap is a two way valve... blowing out is not a problem, but its sucking it back in when it cools down... the system creates a vacuum... if the cap doesn't seal properly on the filler neck, this wont happen, so its constantly pushing the coolant out, but not refilling the system....

Check the filler neck is not corroded excessively... take the cap off and look down at where the cap should seat....

[easty-5]

So is it normal for the rad cap to let water to the overflow whenever you accelerate?

Once it overheats it also blows the expansion bottle cap off and it does lose all it's coolant. I am pretty certain it is the pipes from hell that are duffed, I am just trying to find out if my rad cap is too?

Cheers
Jamie

[easty-5]

Anyone?

[Dangerous]

...Thats exactly what mine did when it cracked the block for the 2nd time.....

[easty-5]

I bought a block tester and tested it. It came back okay. I seriously doubt the block is cracked, it doesn't overheat enough to suggest that. I can easily take it out for a 30minute backroad thrash and temps will stay okay.

Alls I want to know is, is my radiator cap duff? Lol.

[Razor04]

Mate seriously they are £9 from toyota c'mon just go buy one and try it.

[Martin F]

I have one you can have for free

[easty-5]

Mate seriously they are £9 from toyota c'mon just go buy one and try it.

£9!! Times are hard matey

I have one you can have for free

Will you be around tomorrow morning/lunchtime? I think I have an old Starlet one in the garage and I have been told that all toyota ones are the same size. If the starlet one doesnt infact fit then I'll take you up on that offer. Most kind of you once again

[Razor04]

It needs to be rated to 0.9 bar or higher mate

[easty-5]

It needs to be rated to 0.9 bar or higher mate

Yea the starlet ones are the Type S type and 0.9bar, so the same as the MR2. It should fit - hopefully.

[Si_Crewe]

Was just outside mucking about with my engine so I thought I'd give this a check while I was there...

I get nothing coming out of the rad cap until I press the button on the top of the cap.

I assume the idea is that the system remains closed until the temperature hits 0.9 bar and then, when/if it hits 0.9 bar (or if you press the button) the cap will vent some liquid back into the header tank rather than just dumping it on the floor.

FWIW, my rad cap used to be kinda corroded around the button and the button was very "crunchy" to move.
After a bit of hosing with WD40 and poking at the button it freed itself off so it's far smoother.
Perhaps you have a similar problem?