Pressurised expansion bottle modification

Hi folks. I have a 2002 Jimny hard top (my 4th) and an 2002 Ignis on LPG and think they are both wonderful cars. However, as with all the 1.3 engined Suzukis I've owned, they use coolant. They don't leak it and never have, nor are they attempting to combust it, but when the coolant expands with heat, it goes past the pressure cap lifting the spring and into the expansion bottle and it stays there rather than getting drawn back into the rad. The cap is then obviously preventing the water getting back form the bottle into the rad leaving it low on coolant. When I empty the now overfull expansion bottle back into the rad, there is always enough coolant to top the rad back up and leave enough to reach the MAX line. My last JImny did this for over 60,000 miles in my ownership but never got any worse, never did the h/gasket in. I've checked for contaminant in the water (none), compression checks (perfect) etc. and would take any of my 2 Suzukis on any road trip and be confident I'd get there. But I'd likely have to empty the expansion bottle back into the rad after the journey. This only seems to occur when the car is or has worked hard

So, having had great success with French, Italian, Serbian, and Russian cars over the years that have a pressurised expansion tank for the coolant, and driven them across Europe and back without ever having to top up the coolant, I'd like to explore the possibility of having the same system on my Jimny. Does anybody have any experience of doing this? If so, what were the hassles, did it work well etc.?

Thanks or "Diolch" as we say here in North Wales    

 

Welcome to the forum. Have you checked that the coolant feed pipe to the expansion bottle is clear of the bottom of the expansion bottle, they can vacuum themselves to the bottom if they're almost touching?

Lambert may have given you the answer, the Jimny system works well if everything is functioning.

But yes I converted a troublesome Reliant Scimitar from "spit it out,suck it back" expansion system to a pressurised expansion tank.

Yes it worked very well.

The hassles:

1) Finding a suitable expansion bottle that could be mounted slightly above the engine. I wanted a clear bottle so that I could instantly check the level, this meant I needed to find one from a donar car, not an alloy tank.
2) Makeing sure the new expansion tank pressure cap matched the requirements of the cooling system. They have a "blow off" PSI rating.
3) Fabrication of a "T" feed to allow coolant into the system. On the Scimitar I placed this in the radiator bottom coolant pipe.
4) Making a blank cap (no function) for the original radiator cap.
5) The last connection is the original "blow off" pipe to expansion tank, this hopefully is the same pipe ID as your tank, otherwise you need an adapter to cater for this pipe size difference.

So worth the hassle on the Scimitar which had flaws in the system, but not something I have considered  for my Jimny.
 

90% of the time this symptom is caused by a defective radiator cap, I've also seen it caused by a crack in the cap of the expansion reservoir.

The system of the Jimny is widely used in motorbikes and usually works fine.
When the car cools down and the cooling water contracts your car obviously suck air and not cooling water, but when the cooling water expands you do not see that it drips.
Therefore I would check the connecting hose between the radiator cap and the bottom of the expansion bottle. Maybe there is a defect of the pipe inside the expansion bottle, more on the top.

Cheers all and thanks for the pointers. I'll check for the pipe being too low and will check the cap as well, but the system holds pressure overnight so not sure; however, it is an easy thing to check and eliminate as an issue so well worth doing. 

I think the expansion tank to use would be a Fiat/Yugo/Lada/FSO one as they're not that tall.  

I wonder if you will run in to pressure problems?

At the moment it is the radiator cap which controls the pressure, it releases when the pressure gets high, caused by the expanding fluid, and allows the fluid to go in to the expansion reservoir.

If you replace the expansion reservoir with a pressurised expansion bottle, will you then have two pressure release values, one on top of the radiator and one on the expansion bottle? Or do you remove the one on the radiator?

If the pressure release on the new expansion bottle is set to high for the Jimny you might then get something else fail in the coolant system by going over pressure.

You might also have a mounting problem, the radiator cap in my Jimny is just below the bonnet and I understand that the expansion tank in a pressurised system is to be at the top?

What do you mean by the system "holds pressure overnight"?

The only pressure in the cooling system should come from the expansion of the coolant as it warms, so once the engine cools, the coolant should contract and there should be no pressure.

If you have pressure in the cooling system with the engine cold that would suggest a leaking head gasket or similar.

Agreed, holding pressure over a prolonged period is a symptom in and of itself. Is this pressure something you are applying to the engine for testing purposes or is it something it's doing itself?

Thanks all. The Ignis now has done the same again but I hadn't realised I needed to empty the tank back and it got a bit hot driving back from Cardiff through the the mid-Wales mountains. I've noticed that once they lose water, the gauge can still read OK so I guess the sender is fairly high in the system. Anyway, I limped it home and will try another cap and check the expansion pipe is clear of the bottom.

Interesting about the overnight pressure. I had the head-gasket done on this car last year including a head-skim. For only the second time ever, I paid a garage to do it and it cost more than the car is worth, by quite a margin. It's the fact that the Jimny does it as well and so have my other ones. Weird! I'll have it pressure tested by the garage that fixed it and see what's what.

Thanks again/Diolch eto