Hello.
Same problem as a few folks have no doubt encountered. The inside of the expansion tank cap stays in the tank top when I unscrew it. Lid unscrews but leaves the valve housing inside the tank. Bought a new one which lasted about 3 unscrewings and now that one has done it too. Anybody know why there is too much vacuum sucking these interior lids down.
By the way I know you can just pop them out with a screw driver but I'd rather fix whats keeping them in too tight.

Cheers

 

Have you checked the line to the atmospheric catchment tank behind the R/H wheel. I imagine if you had maybe a collapsed hose it might allow coolant in one direction but close off under vacuum while things are cooling.
This could be checked by removing that hose connection at the expansion tank and check with a bit of blow and suck.

 

I have had trouble with this ...the cap has two valves ...a 15 psi to presurise the system and a low pressure return for the expelled coolant.. I find the expelled coolant goes down the long pipe to the tank and does not get sucked back. I was losing coolant every time I drove the car. I have fitted a small tank alongside the main expansion tank for the overflow and it works well.
In your case I suspect the overflow pipe is blocked ..blow it through .you can hear it bubble behind the right wing.
Far too far away in my opinion.

 

Thanks for your answer. So are you now bypassing the original overflow tank ( the one in the U.K drivers side wheel well ) for one you have made yourself and located it closer to the expansion tank? If so, it sounds like a good fix ( shorter distance to travel ) and if so what size tank have you used? Perhaps you could send a couple pictures of your remedy tank please.

Cheers to you both for your replies and help.
Ste

 

My expansion tank saga is this ..BUT remember the original system should work OK as its in thousands of cars.
Every 4 or 5 drives I needed to put about a cup full of coolant in the expansion tank, It did not seem to be sucking back from the overflow tank. I blew down the pipe and could hear it bubble in the bottle and I sucked with a length of clear tube and it came up from the tank ..you should do this. Also I tested the return valve in the cap. Wash it in water and then suck on the o ringside with your mouth . You should get a small airflow thro the cap..thats the return valve . Now my car has an extra electric heater pump that occupies space between the expansion tank and the bulkhead. As yours is standard you could fit a small bottle in that space . In the UK milk bottles are plastic 1/2 litre 1 litre but any old bottle will do . Put one in and hold with cable ties for a test and run a clear pipe from the outlet into the very bottom of the bottle . Put about an inch of coolant in it and besure the pipe is under water. That worked for me . Not an ideal place at the top of the hot engine compartment due to potential evaporation.
At present I am designing a tank in polystyrene which I will cover in fiberglass and melt out the poly with petrol.
But remember the original system should work. Personally, I think the pipe on it is too long and discharged coolant runs down it leaving air in the pipe and only air in the pipe is sucked back .But it works for 99% of us so ????

 

Thanks for that detailed explanation and how to. I got too busy this weekend but may get a chance to look into next weekend. So I presume you are running a temporary recovery tank while you fabricate a permanent one. From that I would conclude that it works.
Thank again. God Bless.

 

Works perfect ..the expansion tank is full to the top every time I check it . Thats important .you fill it to almost overflowing before you put the cap on. I am looking at one of those water bottles people carry to put behind the throttle body . ( mI have a bosch electric pump for the heating right behind the expansion tank.)

 

Do not do what Pistnbroke is suggesting that is an unnecessary bodge ! NOT a repair.
It should, and does, work perfectly as it is designed, unless you have a problem with the hoses etc.
Do as baxtor suggests

I suspect that Pistnbroke may not have correctly primed the system and/or has a coolant leak that needs rectifying, as it sounds like on cooling there is possibly not enough coolant in the Atmospheric Recovery Bottle to fill the system and it is sucking air !

 

Loads of fluid in the tank had a look and bubbles when blown thro and I can suck up fluid.
What do you mean by prime the system ...not seen notes on that .
True its a bodge but it keeps water in the tank until its sorted.

Who is Baxtor ????

 

baxtor is the 1st reply at post #2

There are several methods people have described in the past to prime the Atmospheric Recovery Bottle and make sure that there is at least 1 pint of coolant remaining when the system is full.
Using a turkey baster type system to feed coolant down the overfow pipe or by repeatedly squeezing a radiator hose while covering/uncovering the expansion tank with your hand (pumping) keeping it topped up between squeezes, sorry I don't know the official way but suspect it involves accessing the Atmospheric Recovery Bottle itself.

 

I will try that ..from what I remember about 1 inch in the bottom at present..+ I guess it sloshes about if too little in the bottle and lets the tube drain by gravity. If overflows with too much no harm done.
think the OP problem is a faulty cap.
thanks

 

the distance is only obliquely an issue, as it can be blocked somewhere along it’s length, or it may have a leak somewhere along it’s length which makes it lose the needed vacuum it must have in order to function. The loss of vacuum due to a hose leak is usually the cause of coolant loss as the coolant will eventually overflow the recovery tank since it’s never being sucked back after each cooling cycle.

The length of hose is not directly a cause of these type issues. However with age of these cars, the 20 year old hose can collapse or get a pinhole pretty easily. Otherwise, the vacuum system is known to be very reliable, being used successfully millions of cars.


Z

 

I am waiting on the delivery of some antifreeze before I top up the tank. Once topped up I intend to suck the fluid up ,clamp the rubber link and connect removing the clamp once the cap is on.

 

FIrst things first - you must have a properly-working reservoir cap. My experience with a couple of aftermarket caps convinced me long ago to stick to OEM caps. The aftermarket ones can fail in just a couple of months or be faulty right out of the box. I have been running a 2017 aftermarket reservoir with a 2015 OEM cap for several years with no issues. I unscrew that cap weekly and take a look to ensure that the coolant level in the reservoir continues to remain at the base of the reservoir cap neck. So far so good....

 

I cured my header tank emptying problem by topping up the overflow tank . Poured about 1 litre down the pipe to it from the expansion tank end ...thanks all.