Sensor or airlock.

[STUBIE]

Had a look at the the V6 today as during the week I had the gauge bouncing up and down and the fan going onto high speed mode.

So started it up stationary and had OBD displaying temp. Watched it climb up from cold to about max temp 75 degrees where the gauge was at 9:00am.

Now I have been having the OBD on since I got the HG done and been using the car and it usually sat about 94 degrees when gauge at 9:00.

After a couple of revs I noticed that the temp fell to about 60 and the gauge went down. Left it to climb again again and another rev brought the temp down again, then temp suddenly went to -128 and gauge fell to zero and high speed fan kicked in and only stopped when I disconnected the battery.

I had the the inlet gasket replaced a couple of weeks ago and the mechanic topped up the lost coolant but no vacumn fill. So bit worried about an air lock.

New stat was done with the Head gasket a couple of months ago.

Any feedback appreciated

Stubs

[chrissyboy]

sounds to me like either air in the system or the ecu has had a fit .mine did that about 5 months ago,on mine the gauge went to zero and the hans gauge just showed the c.if you lost some coolant and your guy toped it up i bet he just topped it and got air in there ..i`d have it bleed again if you like the vacum way .. to bleed it the withoutthe vac pump is hard if you dont know what to do ..could also be a dodgy temp switch

[COLVERT]

I agree with the post above. I think you still have some air in the system.
Think you might need that vacuum fill.


Colvert.

[STUBIE]

Thing is it's been running fine for the last few weeks until monday, I did change the battery over last weekend and I remember trying to put the heating up due to the colder weather and finding no heat from the matrix.

Stubs

[T-Cut]

Sensors themselves rarely give problems (wiring apart). I'd also say it's air circulating in the coolant system.

TC

[andy willi]

sounds like air or a possubul water pump failure have seen the water pump fail where the impellors came off so no water getting round have not seen this on a 75 but could happern


andy

[rrobson]

sounds like air or a possubul water pump failure have seen the water pump fail where the impellors came off so no water getting round have not seen this on a 75 but could happern


andy

could be right andy, its the same bloke who did mine so he has probably used the same water pump.
as for the temp, its pointin towards air circulating the system.
you want to get the pump checked asap as mine was leakng quite badly. i believe it was loose (cant remember what andy said)

[chrissyboy]

i wouldnt of thought the water pump was the problem as the coolant not circulating would cause a build up of pressure and pop a hose by now ..

[COLVERT]

i wouldnt of thought the water pump was the problem as the coolant not circulating would cause a build up of pressure and pop a hose by now ..

Before it "popped a hose " it would empty the engine of water through the filler cap. The cap opens at around 10 psi. and is in the system to release pressure so the hoses don't " POP OFF " !!!


Colvert.
:D

[eddiemc05]

defo not impeler failure as water would boil in the block area very quickly and the cap would let out or firstly blow a hose, i would agree that of an air lock probably in the matrix, whats the heat like in the cabin? i would get er bled stuart!

[rrobson]

when mine failed, it was still circulating coolant, but the pump was starting to come ayay from the body, and the impeller damaged the seal.
i found this to be a problem one night when i heared the medium speed fan come on. i stopped straight away and put a few liters of water in (i always carried 2.5 litres of water, tools and oil around) which got me home. overnight a puddle had formed under the car so i stripped it down and narrowed it down to the pump.

Before it "popped a hose " it would empty the engine of water through the filler cap. The cap opens at around 10 psi. and is in the system to release pressure so the hoses don't " POP OFF " !!!


Colvert.
:D

the cap should open just 24 PSI according to my pump (actually, you can pump new ones upto 28 which will releave to 24 and hold it) and all which i tried other than my faulty one held at 24. the old ones according to my pump (the grey ones) open at around 16/18 psi

[STUBIE]

Thanks for the replies guys.

Just for info new water pump and thermostat done with the belts and Head gasket in May time.

If it's an airlock how do I bleed without having a vacuum setup. BTW Lates did a vacumn change when I had a new rad fitted about 6 weeks ago bit since then as I say the inlet manifold gaskets have been changed to OE ones, due to high revs all the time.

And cannot see any fluid under car, well not when it's dry, but I did a small top up the other day.

Definitely started when I tried to get heat out of the heaters last week.

Stubs

[STUBIE]

On trying to bleed the coolant today and sqeezing pipes I seem to hear some squirting sound around the Stat and the I see some white powder sitting around the top. surely the stat hasn't gone in 3-4 months?

Stubs

[chrissyboy]

Before it "popped a hose " it would empty the engine of water through the filler cap. The cap opens at around 10 psi. and is in the system to release pressure so the hoses don't " POP OFF " !!!


Colvert.
:D

that would all depend on i there was a blockage and the presssure could not reach the cap to escape .. if it was ok for a few weeks it is possible that cra in the system has been moved round and has built up and created a blockage ...i myself had a hose pop cos there was a blocage before the cap .. so it couldnt escape the pressuse just built up and had no where to go ,so popped the hose ..

[T-Cut]

Just re-read the first post. The OBD showing a drop to -128C is a clear sign that the sensor or it's wiring/connection is faulty. There is no other possibility that a circulating air bubble would create this reading. Check the sensor/wiring.

TC

[STUBIE]

I would understand that T-cut if the OBD confirmed that the car got to 90 or so degrees when at 9:00 o' clock position on the gauge before the gauge falls to 0 and the OBD states -128, but the car only gets to 80 odd degrees and then when I rev it it it can fall 10 degrees straight way.

Now I'd rather have an under cooled V6 than on over cooked one.

I bought a new temp sensor yesterday thinking I could replace it to rule this out but how the heck can you fit it without taking the manaifold off?

Stubs

[kaiser]

You should firstly check and see if you have enough water in the system.
If the temp sensor sits dry, it is possible that it might give odd readings.

If you loose water, the most likely place is the thermostat housing. They can leak from day one, if there is a problem with the welding/glue.

Don't ever assume. Check.

[STUBIE]

Definately got enough water in the system, topped up yesterday after loosing a bit trying to bleed through the bleed screw, actually undid it that much that I had a water spout and the screw fell into the engine somewhere, had to go to local breakers to get another.

I was thinking, could this be down to a connection problem with the sensor plug i.e. as the engine gets hotter the sensor plug connections expand then looses connection, sensor seems to be correct when car just started and engine cold.

I don't see any coolant in V when cars running there is just a ring of white powder sitting on the top ring of the coolant. All pipes feel hot.

Stubs

[kaiser]

The water needs to be checked cold. You might have enough, but only a check will confirm.
There is no need to bleed these cars. Just give it a run with the heater open, make sure that the engine gets to operating temperature, let cool, top up. You might have to repeat.

An air lock is air trapped while filling. Once remidied, if it re-occurs, it is because you have lost water, either externally or internally.

It is not clear where the white ring is found, but it is possible that it is around the filler cap. These are also prone to wear and should be replaced when tired, where they will let water out prematurely.

I doubt your temperature sensor is the problem per se.

[chrissyboy]

have you got a hans temp fitted ? mine gave a funny reading and rover temp gauge went to zero ..its done it a couple of times now but not since the system eas bled properly .. when bleeding trying blowing in to the header tank to and make sure the water runs out of the bled screw in a continuous motion..to finish bleeding turn off the heater .. then the gauge will sit at the just under 9 o/clock postion.as said clean the area around the stat so its easier to see if its leaking, failing that the easiest way to find any leaks is a smoke test,if leaking the smoke will escape where your losing the coolant ..good thing about the smoke test is its engine friendy much better than any pressure test.
remember that you wont be able to bleed the entire system properly until the stat opens at around 88c then you will be able to bleed the entire system.

[chrissyboy]

The water needs to be checked cold. You might have enough, but only a check will confirm.
There is no need to bleed these cars. Just give it a run with the heater open, make sure that the engine gets to operating temperature, let cool, top up. You might have to repeat.

An air lock is air trapped while filling. Once remidied, if it re-occurs, it is because you have lost water, either externally or internally.

It is not clear where the white ring is found, but it is possible that it is around the filler cap. These are also prone to wear and should be replaced when tired, where they will let water out prematurely.

I doubt your temperature sensor is the problem per se.









attention .... non bleeding of these systems will result in serious over heating problems ............ these cars have to be bled and bled well....

[STUBIE]

Well my diagnosis may have been right, the cable for the sensor seems to be backed up on it self when I inspected and as I tried to move the wires into a better route one of the spade terminals flicked off just spend the last hour trying keyhole surgery to get it back on. Ran up the temp stationary an still only going up to 80 or so degrees, will give it a run later and see what happens.

Stubs

[COLVERT]

that would all depend on i there was a blockage and the presssure could not reach the cap to escape .. if it was ok for a few weeks it is possible that cra in the system has been moved round and has built up and created a blockage ...i myself had a hose pop cos there was a blocage before the cap .. so it couldnt escape the pressuse just built up and had no where to go ,so popped the hose ..
Wow !!! Guess you must have left the cap off and a rat got in the system to get a blockage of THAT size.
Sounds like severe lack of TLC for a cooling system to ever get into that state in the first place.
With the correct coolant, regularly changed, the inside of the rad and engine will remain perfectly clean.


Colvert.

[STUBIE]

An update

Well after putting the sensor connection back on I have not had a problem with the temp gauge falling to 0 and the fan on high speed, my thought was that as the engine got warmer expansion cause a disconnection.

I have run it a few times back and forward to work with OBD and most of the the time it sits on 90-92 going up to high 90's when stationary.
I haver heat through the drivers side vent but passenger side is still cold so going to get the matrix flushed.

Stubs