Sorry if this is in the wrong area but I was wondering if anyone with any knowledge of cooling systems could help me...
I've got a 1990 T25 with 1z conversion and I've been looking at the cooling system today when I was topping it up. It seems like the expansion/header tank is too low in comparison with the pipe work which runs into the side of the head. Here's a pic...
The pipe which comes off the top of the header tank runs uphill towards the pipe going into the head. It would appear that the water in the pipes doesn't come up high enough to enter this pipe and as it runs up and meets the other pipe it seems like this doesn't have water in it either. It has water in lower down but it doesn't seem to get high enough in the system to reach this bit.
I've also noticed that the valve on the cap on the expansion tank is broken and allowing air in and out when I squeeze the pipes. Not sure if this is right.
I've rambled a bit but I hope that makes sense. Any help would be great.
The cap needs replacing as you are at present running an unpressurized system with that one duff. You should also have a top-up tank (usually behind the no. plate flap) that allows the expelled water to draw back into the header tank. This is most probably why you have air in there.
You have to rev the engine hard to expel the air with the top off and replace the cap whilst still revving hard (You will see the coolant level drop as you rev) You need to do this several times and the air will be gone. But...it will come back if the cap is duff and also if there is no top-up tank.
That said... some people have upgraded their engines and have just used a single expansion tank with no ill effects.
I am surprised that you say that - that cap would just spray coolant out over the engine from the cap, even if it were working correctly. Not the way that you would expect them to do a transplant - maybe the previous owner made changes afterwards.
Don't know the part no... sorry. Don't know if you can read it (old pics)
You have the right cap but from your description it is faulty. The "overflow" tank doesn't have to be the original T25 one, just something to collect any coolant which is expelled when it heats up and expands, so it is sucked back in as the engine cools.
VWMartin wrote:So do I need to fill the header tank to the top?
Yes.
VWMartin wrote:And does the new tank need to be higher or lower than the current one or doesn't it matter?
It does not matter as long as the pipe that comes from the (new) "dalek" cap is set so it is at or near the bottom of the overflow tank (so it can suck coolant back into the system as the engine cools down.
You should really connect up that low coolant level sensor on the top of the header tank too (if you haven’t already) especially as your system is not right at present. You REALLY need that working to warn you of any low coolant level situation (which could wreck your engine) !!
E D I T = looking at the pic again = is it wired up?
Topping up the coolant reservoir under the hatch at the back doesn't add coolant to the main coolant tank. Despite having a full reservoir the coolant level was too low.
When adding coolant recently I had to raise the hatch above the engine and add coolant directly to the main tank.
I read somewhere that you need to rev the engine to get the water through, then do the lid up so it keeps the pressure. if there is air in there then its probably not going to draw water through.
