Thread: Super annoying low coolant alarm going off until car warms up (earth issue??)

Originally Posted by AK83

I'm probably(99.9% chance) going to be home all day again tomorrow, and most likely Friday too(kids holidays week with me) if you want to come around and I can show 'ya.
Shoot me a txt beforehand tho.
Very easy to do too, now that it's sunk in how to do it properly.

We could also try to do some rudimentary electrical testing too, even tho I'm not well versed in some aspects of electrics.

I probably need to sort out that hose before trying to bleed anything because otherwise it'll just happen again, and I need to check if that hose is actually okay and it is just the clamps, or if it's actually a damaged hose end. I've tightened it up a few times and it's still leaking a tiny bit of coolant.

I'm probably out all day tomorrow so maybe Friday morning might be a chance, will keep you posted thanks Arthur

Although an absolute pain in the bum to fit and remove I think that the LR hose clamps are a better option to the standard screw tightening clamps because they are spring loaded and maintain their pressure to hold the hose better.
As long as new ones are fitted each time a new hose is fitted I haven't had any problems with these types of clamps and they never need to be tightened after the initial fitting like the standard hose clamps do

So if I was taking it for a big drive today should I worry too much about needing to give it a bleed or will it be okay so long as I can put up with that noise for ten minutes?

It'd depend on what sort of driving you've done or been doing since the issue started.

One of the reasons I think your coolant bleeding isn't the issue, is that of the few times I've had massive overheating, it's been the result of my less than capable bleeding knowledge.
If you've got air in the coolant I'm sure you'd also have overheating issues too.
Even on short drives just to work, or to the shops or a quick test run to get it to operating temps .. I've mucked up the bleeding program, it's still had air in the system, and instead of settling at about 83°C for the coolant level, it's rocketed to 100°C, and I'm going ...
So, I bleed it a bit more on the side of the road, and still the same issue.

Normally! when the coolant system is all good and I get excessive heat due to running the aircon, the dash temp gauge doesn't budge even a millimeter, and my coolant gauge will show mid to high 90's.
A couple of times with this aircon heating up issue, I've seen 103-105ish on the coolant gauge, and only then will the dash temp gauge start to move.

When I mis-bleed the coolant tho, the dash gauge moves much quicker, and well before 100°C shows on the coolant gauge.
Can't remember exactly, but I do remember a couple of times, where (it stuck in my head) I've seen the dash needle rise at 94°C and 98°C shown on the 1Gauge.

If you have the time today, you could try a quick short bleed.
What I do which works perfectly first time every time now:

Get any old drink bottle and cut the bottom of it to turn it into a funnel. If you have a suitable funnel, even better! But you don't need an excessively large volume. I find a 500-600ml bottle to work fine.
Make sure rad is full. If there's coolant in the reservoir, then there should be coolant in the rad. If you open the rad plug(nut), it will overflow out continuously as the reservoir is higher .. ie. gravity.
So the trick is to only just open the plug and close it up ONLY when there is still some coolant in the reservoir. Don't let the reservoir lose coolant and then close the rad plug!

Then use the funnel/cut bottle on the reservoir, fill it to a mid-high mark on the funnel, make sure your vent heater is on(just in case) .. and the open the plug on the top of the thermostat housing to allow coolant to flow out.
The higher level of the funnel at the reservoir forces the coolant out of the thermostat housing and eventually the air pockets too.
If the D1 is parked on a slight uphill angle it apparently helps too, as it keeps the heater hoses a bit lower than the high point of the thermostat housing.(I haven't tried that yet)

Don't let the coolant level in the funnel get lower than about an inch or two from the reservoir end with the bleed cap loose.
The idea is that you want coolant in the funnel whilst you're closing the bleed cap plug. Even just to the point of it being finger tight. So it's an easy on person two handed operation.
You will end up with a bit of overspill as you'd expect around the reservoir, and the reservoir will be overfull .. but that won't be an issue, it will eventually settle to a level that the system prefers on it's own after a few drives.

Really easy to do and should take only a few mins.
*The thermostat housing plug(the bleed nut/cap/plug/whatever) should be pre loosened.
*Engine coolant doesn't need to be hot! I do it from stone cold.

Remember I'm not a mechanic, but every other car I've bled coolant for, has been engine idling, coolant warm, heat and pressure has expelled coolant from the small bleed nipple/nut/port.
300 Tdi had me confused for ages in using the same method on it. Never worked properly or had to do it a zillion(err. Ok, maybe three or so) attempts to get it to be fully air free. Used to frustrate me no end!
The above bleed description is the best, most reliable way(noting that it was first described by blknight that I recall).

Can I ask if taking the cap off the overflow reservoir, but not opening anything else, and then idling the engine, would force air out through the reservoir on a 300Tdi? Just curious.

Originally Posted by Young Angus

So if I was taking it for a big drive today should I worry too much about needing to give it a bleed or will it be okay so long as I can put up with that noise for ten minutes?

These alarms are there to protect your engine, I personally would get this problem "Sorted" Before using the truck.
Overheating a LR engine can have insanely expensive results.

My alarm, same as yours, was going off when cold sometimes, and sometimes while driving ... intermittent. I had a p-gasket leak and coolant level had dropped 'a bit' in the expansion tank. Topped up the coolant level - fixed. I hope yours is as simple.

Bleeding a 300tdi is easy. Take off cap on reservoir, the bung on top of thermostat housing and the coolant alarm from top of radiator. Fill through thermostat housing until water is at top of radiator (where coolant alarm goes). Replace coolant alarm. Continue filling through thermostat housing until water is at top of thermostat housing. Replace bung at top of housing and replace cap of reservoir. Reservoir will be a little overfull, but the system will get rid of the excess water. It's really that simple and quick.

Tom.