Worried about possible overheat.

JamesBB · Jan 13, 2015

On the way home this evening (which is only a 5-6 mile drive), the temperature started to climb. It got up to half way but no heat was coming through from the heater. I probably average 25 mph on the way home and in the last 2 miles the temp started creeping up to the top of the white section on the gauge. I slowed in traffic at a junction and it started to go into red. Less than 1 mile from home the red light came on then when off and the temp lowered a little back to the top of the white section.

So I must have driven for a mile in the red , but not that long with the light on, that was momentary - well less than 10 seconds.

No steam, no other signs.

Once home I checked under the bonnet and the top hose was very firm, not hard. The heat was not as bad as I was expecting, I thought it may have been quite extreme but it seemed normal.

I let it cool a little and checked for leaks, there seems to be a small dribble onto the top of the water pump but cannot see anything major.
The coolant level was low, lower than min, so I topped it up. Opening the cap it released a lot of air and it bubbled into the expansion tank but to near the low level,it took another half litre to bring it to max.

It has had a new water pump, hoses, thermostat (Genuine LR) and coolant in the last 3 months or so.

I suspect 2 things, a minor leak, and an air lock.
What do you guys feel? Your thoughts and advice is always welcome

I am quite worried.

Thanks in advance.

Datatek · Jan 13, 2015

Petrol? No heat from the heater could be an airlock (or blend motors). Have you checked the viscous fan.

JamesBB · Jan 13, 2015

Datatek said:
Petrol? No heat from the heater could be an airlock (or blend motors). Have you checked the viscous fan.

Yes sorry, petrol 4.6.

I know the blend motors need to be replaced, but I have jammed the sticking heater flaps half open at present, so normally there is a continual flow of heat.

i just checked the pipes again, the top hose seems very soft now, the hose from the left head to the internal heater is very hot, return from the heater is cold.

Viscous fan I will check in the morning with the newspaper test. It has been fine, no issues. But of course I had it removed to do the water pump etc.

Datatek · Jan 13, 2015

JamesBB said:
Yes sorry, petrol 4.6.

I know the blend motors need to be replaced, but I have jammed the sticking heater flaps half open at present, so normally there is a continual flow of heat.

i just checked the pipes again, the top hose seems very soft now, the hose from the left head to the internal heater is very hot, return from the heater is cold.

Viscous fan I will check in the morning with the newspaper test. It has been fine, no issues. But of course I had it removed to do the water pump etc.

So no flow through the heater, could be water pump or the heater could have stopped due to a vapour lock when it overheated.

Saint.V8 · Jan 13, 2015

More than likely an airlock...or no pump flow as Datatek says.

My money is on an airlock....when were the o rings last changed?

JamesBB · Jan 13, 2015

Datatek said:
So no flow through the heater, could be water pump or the heater could have stopped due to a vapour lock when it overheated.

So an overheat without steam may not be the sign of a nightmare I hope.

It could be that the cooler water from the expansion tank top up fed down into the heater return then cooling it, I guess.....

Now it is dark all I can do it wait until the morning and check the state of play.
I may drain the whole thing and refill again as per Rave.

JamesBB · Jan 13, 2015

Saint.V8 said:
More than likely an airlock...or no pump flow as Datatek says.

My money is on an airlock....when were the o rings last changed?

Heater O rings? They were changed out in the spring last year.
There are no leaks from them, or at least the carpet is dry.

Datatek · Jan 13, 2015

It might be drawing in air through the leak you mentioned as it cools.

biketeacherdave · Jan 13, 2015

Datatek said:
So no flow through the heater, could be water pump or the heater could have stopped due to a vapour lock when it overheated.

I think you have just got a plain old air lock in the heater matrix causing your problem. I replaced my plastic T piece today same thing happened no heat from the heater. Iv become fairly good at sorting this one take your expansion cap off pull the right hand heater hose off shove a hose in and turn on only a gentle flow.

Water will eventually come out the metal pipe you just disconnected the heater hose from put your hand over that a thumb if big enuff and wait for water to start filling the expansion tank as soon as it does pull the hose recconect. Run the engine burp your top hose replace cap.

Job done rechech water level from cold the next day. Good luck

Datatek · Jan 13, 2015

biketeacherdave said:
I think you have just got a plain old air lock in the heater matrix causing your problem. I replaced my plastic T piece today same thing happened no heat from the heater. Iv become fairly good at sorting this one take your expansion cap off pull the right hand heater hose off shove a hose in and turn on only a gentle flow.

Water will eventually come out the metal pipe you just disconnected the heater hose from put your hand over that a thumb if big snuff and wait for water to start filling the expansion tank as soon as it does pull the hose recconect. Run the engine burp your top hose replace cap.

Job done rechech water level from cold the next day. Good luck

And if you are lucky, the antifreeze will still be effective

tomcat59alan · Jan 13, 2015

No water flow due to impeller failure on water pump? Do you get flow to the expansion tank from the small pipe?

biketeacherdave · Jan 13, 2015

Datatek said:
And if you are lucky, the antifreeze will still be effective

Lol yep your anti freeze needs to be a good strength iv just refilled mine last week doing the valley gasket I had to do this exact same thing to get the heater going. If your worried syringe some coolant from the expansion tank and top up accordingly with neat anti freeze

JamesBB · Jan 13, 2015

tomcat59alan said:
No water flow due to impeller failure on water pump? Do you get flow to the expansion tank from the small pipe?

The pump is a brand new Airtex one, hope it is ok. Certainly seems to squirt coolant with some pressure from the small pipe at the top of the rad when removed.

JamesBB · Jan 13, 2015

biketeacherdave said:
Lol yep your anti freeze needs to be a good strength iv just refilled mine last week doing the valley gasket I had to do this exact same thing to get the heater going. If your worried syringe some coolant from the expansion tank and top up accordingly with neat anti freeze

Sounds like a plan. I would top up with fresh antifreeze to be on the safe side.

I suppose he heater matrix is the hardest part to remove the air from, so your method is worth exploring. I think this lock has been in there a while, I keep thinking I bled it but the level drops from max to min over a day or so. Must be the minor leak sucking air in as Datatek says.

JamesBB · Jan 14, 2015

Update.

Not much of one as I only had a little time and now it is starting to darken.

Viscous fan tears the newspaper up, it certainly does not get anywhere near slowing the fan.

Lost about a pint overnight. Found another leak coming from around the drain plug and thermostat areas. The drain plug is a new brass one, probably not tight enough. More work tomorrow then.

Cheers

P38Penguin · Jan 15, 2015

If you have one, try pressurising the system with a modified cap and valve, you should be able to have a good poke and prod without burning yourself. Also, if it is an air lock, run the engine with expansion cap off, temp and fans set to max and burp the top hose, that should hopefully encourage the air to escape.

mick

JamesBB · Jan 15, 2015

Update:

Small amount of coolant lost overnight. drips from under the stat and the plug. Small puddle on top of water pump.
Following possible path up from the stat, seems to be coming from the hose attached to the ridged metal hose that goes behind/under the alternator.

I then found a bad hose clip on the rubber hose attached to the metal one. This is the hose I have coloured red in the attached diagram. I drained the system from the rad plug and took the red (in the diagram) hose off. I think it may be ok but I am not too happy with it. I suspect it may not be at its best and aim to replace it.

Does anybody know the part number for this hose? It is just 5-6 inches long and a single 90 degree elbow in it. I think it may be the bypass hose, but not sure.

If anyone can help I will get it on order.

Cheers

biketeacherdave · Jan 15, 2015

JamesBB said:
Update:

Small amount of coolant lost overnight. drips from under the stat and the plug. Small puddle on top of water pump.
Following possible path up from the stat, seems to be coming from the hose attached to the ridged metal hose that goes behind/under the alternator.

I then found a bad hose clip on the rubber hose attached to the metal one. This is the hose I have coloured red in the attached diagram. I drained the system from the rad plug and took the red (in the diagram) hose off. I think it may be ok but I am not too happy with it. I suspect it may not be at its best and aim to replace it.

Does anybody know the part number for this hose? It is just 5-6 inches long and a single 90 degree elbow in it. I think it may be the bypass hose, but not sure.

If anyone can help I will get it on order.

Cheers

did you ever back flush the heating matrix yet ?

JamesBB · Jan 16, 2015

biketeacherdave said:
did you ever back flush the heating matrix yet ?

Not flushed it yet no, I need this hose to do that, still no coolant in there at all. With that in mind I thought it best to back flush when I refill the system to force out any air.

Although maybe it is worth flushing it anyway and feeding the output into a bucket......

biketeacherdave · Jan 16, 2015

JamesBB said:
Not flushed it yet no, I need this hose to do that, still no coolant in there at all. With that in mind I thought it best to back flush when I refill the system to force out any air.

Although maybe it is worth flushing it anyway and feeding the output into a bucket......

no need for that you only want 1 hose dissconnected so it flushes the matrix and cooling system all at the same time any air will come out the expansion bottle. just follow my guide its the only way iv ever managed to get it air free n working

Worried about possible overheat.

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