any way to check the coolant level warning device while on the road?
The one core plug where the block heater would thread in seems to drip sometimes causing me to be short on several litres of coolant. I noticed because the temperature began to climb and drop back down in some situations.
Being on the road is there a neat way of testing the black box that generates the signal should the light bulb be good? I know that it senses the level by seeing if there is a voltage drop from the wire in the tank to ground through the coolant.
Apart from that nothing went wrong in 1500kms since jb-welding in the head gasket and I‘m trying to stay positive. I finally have a club membership for towing.
The only other annoyance is that the driver’s window failed and it burned my fuse so it stays shut now.
David,
If your ignition switch is ON and the coolant is at the proper level in the brown plastic header tank then the Low Coolant light on the dash should be extinguished. If you then remove the White-Red wire from the Low Coolant Level Sensor in the Header Tank the Low Coolant light on the dash should illuminate in a few seconds. If your system does not work this way then something is wrong.
As Aristides points out this is a test that you can performon the road.
BTW, there are no fuses in the window circuits. The usual problems are caused be dirty switches. Lots of info in the archives.
That makes so much sense. Thank you both!
How could I not think of that
I‘ll keep an eye out for the something. I think either the in-tank metal got contaminated by the remaining oil residue or something in the wiring/black box out of my control. Tomorrow will tell, good news is coolant loss went down significantly.
The window switches are not at fault; I tried my luck and tested other switches that work. Maybe a wire shorted to ground or to the other or the motor is toast… I disconnected it and customs thought it was funny that we had to get out in our posh rattle can.
**
To rely entirely on the ‘low coolant’ warning light is fraught, David…
The best warning signal is unaccountable temp gauge readings. At which stage it is prudent to stop and check coolant level, using due caution with a hot engine. To check the function of the low coolant warning at this stage is pointless - it should be checked at home, as should the coolant level…
That said; either you have not followed up an obvious leak with regular checks on coolant levels - or the leak is of a magnitude that requires urgent action. You need to observe coolant levels regularly over time to assess how much fluid is leaking.
‘Several litres’ of coolant does not disappear overnight unless you have a major problem - ‘drip sometimes’ is no explanation…
An assessment of coolant loss allows you to carry a spare can of water of suitable size - and drive on…
It might have disappeared after several hundred miles, Frank, and I was very careful to slowly open the cap. As long as the engine runs, there is no boiling over, luckily. With the erratic needle we immediately pulled over and I already knew what was going on. I hope it is what it seems to be - that threaded core plug. The leak has slowed down so it has presumably blocked itself with the available debris. Drip sometimes was about a few drips a minute - add that up over a few hours and you get this kind of leakage.
A side effect of a leak is that system pressure is lost. Which does not interfere with cooling, but lowers the boiling point of the coolant. Also, if enough coolant is lost; the gauge temp sensor is not heated by the coolant - and the gauge may seriously underread actual temps…
This is why I am so annoyed at the level sensor failure. The indicator lamp has to work. Properly.
It will leak most with the highest pressure, by the way, and that should occur a few minutes after shutdown. Heat soak
And I looked after shutdown and couldn’t find water nor steam, so far. No residue either. Just what little had pooled on the aluminium bracket that supports the pump and what had trickled to the ground in the earlier leaking stages. I‘ll shop around for a satchet of barrs‘ leak stop just in case…
For everyones‘ entertainment and relief, the XK tolerates the loss of several litres (quarts) of coolant very well
thanks for pointing out that there has been technical evolution over the series Jags production. SII cars don’t have this warning light feature. Yet, even without any bit of knowledge about your system I’d be surprised if the coolant level warning light were ever to function properly with a running engine.
A friend of mine lost two Mazda engines due to animal induced coolant leaks: upon start coolant level was still ok. With pressure building up and the water pumped through the coolant left the system quickly and even water temp didn’t react any more as the water temp sensor relies on water - not hot air.
Frank’s point is still pertinent - you’re talking about a lot of coolant! I doubt that even a few drips a minute would make several litres of coolant over just one trip. Maybe under load conditions there may have been a more or less constant loss of coolant.
Jochen, there is a black box behind the glove box. It measures the resistance of a wire that connects to the plastic reservoir tank (where you fill up) to ground. If current flows, there is water that can conduct the electricity; so if I disconnect the wire the light must turn on. If not it is a more difficult fault. The bulb seemed fine.
The BMW was close to that once, it went to full hot all of a sudden when we went downhill and the 120+°C water reached the sensor - and I added about two litres. Similar story a year later in Italy but it still runs very well, luckily.
Depends on trip length, I might have emptied more than both tanks on the trip in question - maybe…
I am talking about a shockingly high amount of coolant but as I said before the leak seems to habe plugged itself, who knows how bad it was.
Thank you for the wishes; I seem to rely on good luck. So far I‘m very happy.
**
Again, David; check coolant level, engine cold, every day for some time. If the engine is not driven, it gives the ‘stationary’ leak rate - the longer it stands the more precise the measurement. Then check before and after driving, engine cooled down - it will give the ‘driving’ loss. And the difference may be of interest…
It’s essential that the expansion tank is only replenished to the ‘normal’ level - filled up fully; a litre or so is inevitably lost at the first heat sequence. With the expansion tank full, the 15 psi cap opens as soon as the coolant starts heating up - and without a leak, pressure stays at 15 psi throughout. From ‘normal’ coolant level, the pressure gradually rises, to 15 psi with the engine hot - providing there are no leaks…
All this is of course just preliminary - it does not resolve the leak cause. Filling up the expansion tank and then idle the engine hot, while closely observe for leak points, may show something as the pressure increases. The better alternative is of course to pressurise the system, for a more leisurely observation…
Incidentally, if coolant is low due to a leak, the pressure is lost. And the heat soak is ineffective as the hottest part of the engine, which causes the heat soak, is drained of water as the engine/water pump stops…
Coolant level unchanged.
The box wasn’t plugged in right for good reason, now the lamp is on continuously. The connector is JB-welded into the tank and I won’t disturb it until home.
I still think the highest pressure occurs after shutdown.
**
With normal level from cold; the pressure will rise as coolant heats and expands - reaching 15 psi (cap relief pressure) as the engine reaches operating temp - and stays there…
If coolant temps drops, so will pressure as coolant cools and contracts - but if temps rise the further coolant expansion will open the relief, venting coolant out, maintaining 15 psi. So the pressure cannot rise beyond relief pressure. The heat soak may cause venting coolant - but the small heat soak temp rise is minimal anyway…
With lost coolant, the pressure will not stay at 15 psi. And again the heat soak when stopping the engine will cause little coolant expansion and minimal pressure increase from well below 15 psi…
Fill up when cold. At the first heat up period the water expands and excess fluid is pushed out the cap.
From that point on the relief cap should only open when pressure exceeds 15psi; that should not happen when the engine is running. When it is shut off, coolant temperature will rise as there is no cooling but the heat from the internals still transfers into the water. There is of course the catch tank but let’s leave that out of the picture - the cap should stay shut after the first operation and should not allow steam to escape. It is a safety device, not a pressure regulator!
The heat soak increase is in the double digits and will cause a significant pressure increase. With lost coolant, if anything the pressure will increase as there is much more steam generated and less coolant capacity available. Still, the cap will only open when 15psi are exceeded, and in heat soak temperatures this should not happen, otherwise we’d have to refill often losing a few mililitres every time we shut the engine off, several pints a year.
Still, the pressure will be the highest after shutdown due to the heat soak and any leaks should be most noticeable a minute after shutdown, at least that is what I maintain. Minimal, sure, not much but still an increase. We should measure just to find out
I’m happy to note that I have not lost any coolant in the last 200 miles.
**
The purpose of the pressure cap is to raise the boiling point of the coolant from 100c to some 120C by rising pressure to 15 psi, David - considered a reasonable safe pressure for hoses and connections…
As pressure is generated by coolant expanding with heat, it cannot indeed maintain 15 psi if the coolant temps drop - but it will vent excess pressure whether, importantly, it is caused by liquid or steam. I never meant to imply that the pressure cap could raise pressure - which is a function of coolant volume…
Temperature is created, and maintained as will pressure, by engine heat while running. If temp varies so will pressure, but the highest temp reached will dictate the residual coolant volume - excess will be ejected as the hottest coolant is the most expanded…
If the heat soak temperature is higher than previously reached, the pressure will rise, but reaching 15 psi; venting will occur - first time around. However. it is not unusual to reach higher temps during driving, causing venting, then dropping as one approaches home. Highest pressure is then reached during driving…
A typical pressure leak is at hose clamps, and may indeed start as pressure approaches 15 psi. But there is no guarantee that this pressure will only occur during heat soak.
The best way to detect a pressure leak, apart from pressurising the system by air pump, is still to top up the system cold. Then idle the engine to operating temp while observing for leaks. During this period the pressure is constant at 15 psi - while coolant is expelled. At other times, the pressure may be 15 psi - or lower…
Since you now don’t loose coolant - the question is now somewhat academic…
