NA coolant system pressurising?

[Si_s Supe]

Hi all,

 

Just got home from work and wanted to remove my broken fan shroud to carry out a repair. Quickly realised the top rad hose needed to be removed for this. I gave the hose a bit of a squeeze and it feels pressurised! The bottom hose the same. Pressure seems to be dropping as the temperature lowers. What souls be my first port of call to check?

 

There are no adverse symptoms. No over heating or hissing after use. I'd never have known if I hadn't squeezed my hose!! (Ooh err!)

[Dnk]

It is meant to pressurise, thats how the system works, what rating is the rad cap ?

 

As the water heats up goes the pressure, when it reaches the rating on your rad cap the rad cap

releases the pressure by letting coolant out into the expansion tank, when it cools the pressure

drops and the coolant is drawn back into the rad.

Edited April 15, 2014 by Dnk (see edit history)

[Si_s Supe]

Ah, makes sense. The hose just seemed to be a lot harder than I'd expected. It says on the cap 1.1 (I guess that's bar?)

 

 

I've just done a 35 mile drive and the hose is almost solid. This photo, although not great, shows me squeezing the hose pretty hard. I can compress it only by around 10mm.

 

[scott87]

Thats the right rad cap for an na

[Dnk]

Well 1.1 bar is 16 psi

 

Is the cap working as it should and letting coolant out when its hot then drawing back in when cold ?

 

Check the level in the tank and see, mark it with a felt pen/marker pen when its cold

then run it up to temp and check where the level is

[Si_s Supe]

I'll do that, cheers. I remember when I had my turbo, the relief valve in the cap disintegrated completely. When the car has cooled, I'll give it a good check over.

[Pulley]

Also, to check for hg leak, start the car from cold and having released any pressure in the radiator first

Then after a short time of idle check the hose, it should be soft and not pressurised

[Si_s Supe]

So this morning I've done all of the above. Released the rad cap and it's quite manky underneath.

 

 

Sucked some coolant from the expansion tank and it looks to be a good colour to me?

 

 

There is some scum in the tank though.

 

 

The stuff in the rad however looks to be a rusty colour.

 

 

Anyway, closed everything back up and started the car from cold. I'd say the pressure in the hose was building within 1min but so was the temp. You could feel it getting warm. By the time it was at normal running temp. the hose was solid and the rad cap doesn't seem to have opened as the level in the tank didn't change.

 

Just ordered a cap, will be here today so let's see if that helps!

 

I'm guessing the system really wants a good flushing at some point in the not too distant future.

[Dnk]

Time for a coolant change and flush the system, if you do that i'd fit a new

OE rated thermostat as well, on the TT they're 82 C and think its the same on

the NA

Edited April 16, 2014 by Dnk (see edit history)

[Si_s Supe]

Time for a coolant change and flush the system, if you do that i'd fit a new

OE rated thermostat as well, on the TT they're 82 C and think its the same on

the NA

 

Yep, I think you're right. I remember reading on a thread somewhere that Mr Wilson said it's not really worth using the red 4Life coolant, but using a decent concentrate of the same type and deionised water. I can't find that thread now, what type of coolant does the car need?

[Chris Wilson]

Any ethylene glycol based concentrate is fine. Unless you live in an area of hard water, tap water as a mixer should also be fine. Try blowing a bicycle tyre up to 16 PSI, then squeeze it. That hose seems quite normal.

[Dnk]

Glycol Ethylene pre mix or concentrate mixed with distilled water

[Guest Roger NE]

I don't think it's possible to buy antifreeze that ISN'T ethylene glycol based these days (they stopped using methanol years ago) . . . what's really important is all the corrosion inhibitors they add, but again all antifreeze has them. You actually need those qualities more than the actual antifreeze (it has to get VERY cold to freeze an engine!). It's why they get so many BHGs in hot parts of the USA - because stupidly some people just use water.

 

But most Antifreeze comes "ready-mixed" now, so beware of that ! It's usually a 50/50 mix, and at least it saves adding water. (personally I shop around the Supermarkets, to see which have the best deal - you can sometimes find ready-mixed for £1 a litre)

 

If you DO buy the concentrate, I personally wouldn't bother buying distilled water to mix it with . . . but I've always used boiled water out of a kettle, that I've then put through a Water Filter Jug (gets rid of most of the calcium in it).

Edited April 16, 2014 by Roger NE (see edit history)

[Si_s Supe]

Right on que, there's Chris!! Thank you. And thanks for all the responses. Very helpful. I'll change the rad cap anyway as it won't hurt and it's probably original anyway!

 

I guess it's best to whip the thermostat out for an open system, go in through the water hoses up at the bulkhead with a hosepipe and run the engine to flush system through?

[stevie_b]

If you DO buy the concentrate, I personally wouldn't bother buying distilled water to mix it with . . . but I've always used boiled water out of a kettle, that I've then put through a Water Filter Jug (gets rid of most of the calcium in it).

Surely using boiled water is worse than using water straight from the tap? When you boil the kettle, the steam is the bit you'd really like - condense it into a cold container, and you've basically got distilled water. The water left behind in the kettle will have a higher concentration of calcium and others bits 'n' bobs than unboiled tap water.

 

I suppose using boiled tap water in a soft water area means you'll have killed off most of the bugs in the water, so less likely to get algae etc.

 

Edit: just re-read the bit about using a water filter to remove calcium etc. Kind of makes sense, although I don't know how effective those water filters are.

[Guest Roger NE]

The calcium tends to come out when you boil tap water, and collect in the bottom of the kettle, or stick to the element if it's visible.

 

Even the built-in simple mesh filters in most jug kettles will keep a lot of the bits out.

[Si_s Supe]

Quick update, I changed the rad cap on Wednesday with absolutely no difference what so ever! In fact, I took the car for a good blast Wednesday evening half expecting to end up with a coolant pipe splitting, but it didn't.

 

I'm guessing, as said above, I'm talking myself into thinking there's a problem where there's not! I just can't help but think those hoses are harder than they should be.....!