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

Originally Posted by Kerry

The sensor should not be at the thermostat housing because the pump keeps sending coolant onto it long after you have dumped a lot of coolant. I had mine there and found out the hard way. It must be at the radiator filler plug. If it is an Engine Saver, you can find out more on their web site.

Me thinks you had another issue of some kind.

Are you suggesting that the waterpump flows coolant directly into the thermostat housing?

Water pump coolant flows into the block, not the thermostat housing.
So while you're correct, it's the same as almost every other system .. once you have low coolant levels, you start getting overheating.

Technically it shouldn't really matter if it's fitted in the thermostat housing or radiator cap.
If you have sufficient levels of coolant to maintain an acceptable temp in the engine, then low coolant or not, it makes no difference.
If the coolant level is too low to maintain an acceptable engine temp(ie. not overheating) then a coolant temp gauge will display the same problem.

Low coolant alarms are all well and good, but I'd prioritise an actual working coolant gauge first, and keep an eye on coolant temps.

Hey Yangus
You havent voted in the ‘what landy do you currently own’ poll
It is in the general chat section

Originally Posted by edddo

Hey Yangus
You havent voted in the ‘what landy do you currently own’ poll
It is in the general chat section

Oops I'll get over there right now...sorry I haven't had much time for the forum this last week, been back at work and run off my feet...I just want to go driving I don't want to have to work so darn hard!

Originally Posted by AK83

Me thinks you had another issue of some kind.

Are you suggesting that the waterpump flows coolant directly into the thermostat housing?

Water pump coolant flows into the block, not the thermostat housing.
So while you're correct, it's the same as almost every other system .. once you have low coolant levels, you start getting overheating.

Technically it shouldn't really matter if it's fitted in the thermostat housing or radiator cap.
If you have sufficient levels of coolant to maintain an acceptable temp in the engine, then low coolant or not, it makes no difference.
If the coolant level is too low to maintain an acceptable engine temp(ie. not overheating) then a coolant temp gauge will display the same problem.

Low coolant alarms are all well and good, but I'd prioritise an actual working coolant gauge first, and keep an eye on coolant temps.

I sure did have 'another issue'! My P gasket started leaking S of Alice Springs on my way back to Darwin towing 2.9 tonne van. In A/S i bought some Rislone radiator stop-leak and as soon as i hit the first hill just N of A/S i boiled - and did so every time i hit a hill or got to cruising speed. My heater element blew (bypassed that) and exhaust gas was bubbling into the coolant header tank. I learnt that if i kept the exhaust gas temp below 380C it would not boil - so it was a sloooow trip to Darwin, especially up the hills (sorry road trains!). I put a new Turner performance head from England on (it got to D before me) and had the 3yo radiator cleaned - it was 70% clogged. I will never use a radiator treatment again! Despite boiling several times and losing quite a lot of coolant, the Engine Saver alarm never made a noise. Later i spoke to David at E/S and he alerted me to the fact i had the sender at the wrong place and it was he who told me about the water pump keeping the sender asleep when it is at the thermostat housing. Interestingly, after 440,000km each bore was in perfect condition with honing marks still clearly evident. All is good again.

Originally Posted by Kerry

.... Later i spoke to David at E/S and he alerted me to the fact i had the sender at the wrong place and it was he who told me about the water pump keeping the sender asleep when it is at the thermostat housing. .....

That part doesn't make sense.
Of the info I can find on the coolant flow in a Tdi, the only way the water pump can supply the thermostat housing with water is via the block and head.
The small hose from thermostat housing(passengers side) to the water pump is the bypass that is open when engine is cold, and blocked when engine is at thermostat operating temp.

So coolant flows from pump through engine(and heater core) and back to thermostat housing, and when cold, directly back to water pump.

300 tdi hold about 11 lt of coolant.

it's be in interesting test(from cold) to see if the the bottom rad hose was removed just a little at a time, say to remove 1lt increments, what would be the result of the low coolant alarm's indicator if it were fitted in the thermostat housing or radiator plug.
That is how many lt removed in each location would set it off as the warning.

Not so much for me... I'm not a big fan of low coolant alarms myself... just curiosity on my part. Practicality would imply that the sensor set up at the highest point of the system(which is actually the top heater hose at the back of the valve cover! ) would make the most sense .. low level sense at the earliest point in time.

Of course I may have my understanding of the flow of coolant in the 300 Tdi completely wrong too tho.

on a separate but similar front: I had a leaky P gasket a few weeks back .. worried me half to death as I'd only just replaced the water pump.
Checked the three long bolts on the waterpump and they must have come loose. Torqued up when I installed the pump, but early one morning with motor still cold, I gave them a double check and they were almost totally loose(not quite, but a nip up with a open ender showed them tighten up as if only half done up!
When I do torques, I always double check the bolts .. anyhow, re did them, + about 5-10 Nm over(can't remember the value off hand now) .. but I was then off on my little drive .. and no problems with the P gakset.
That was on the 27th Dec.
Having a look into the P-gasket issue .. what an abomination of a design choice!! .. I got a spare gasket now myself .... just in case

So I went away with the Disco last weekend, spent all weekend up in the High Country on tracks , lots of low range and probably worked it petty hard with no issues. Hot days too.

Got home and the day after I got back this low coolant alarm started going off again on start up same as before.

I took out the bung in the top of the radiator and it looked dark and kind of corroded again so I got out the trusty toothbrush and gave it a clean with some jif and put it back in and voila...no more alarm!

This was not long after I cleaned it last time though and I can't help wondering if there is something in there that's corroding stuff. This only started happening after I had it serviced and coolant changed etc. Come to think of it, it started happening a few weeks or so after the service...kind of a similar time frame to when this one started happening after I cleaned the sensor last time.

The coolant they put in is green and this is the guys at Uptech and they definitely know what they're doing, at least Tony the boss man does, he loves old Discos and particularly the 300Tdi. So I have no doubts they did it properly but this is just weird.

Is green coolant just green coolant...or are there different types? One that could be the wrong one for this motor and start corroding stuff?

Did they specify on the invoice what coolant they used, or did they just list it as 'coolant'?

It could be electrolysis that is affecting the sensor.