suspected coolant pump

bear-mg · 21st August 2015, 16:36

I managed to finally get around to refitting my rebuilt turbo to the zt , started the old girl up , she was slightly reluctant at first as she has been sat for nearly a year so the previous owner tells me ...all was going well , the old oil residue in the exhaust was burning off nicely , I noticed the I could hear the water pump which sounded like the bearings were a little noisy , I had the dash set to number 7 on the obd function so I could keep an eye on the coolant temp , rad cap was of to bleed any air out as unfortunately I couldn't undo the bleed screw as it felt like it was going to snap ...i left it running for a while with the rad cap off , then put the cap on ,which made the temp shoot up

.....before i put the cap on I couldn't see any coolant coming out of the small return pipe to the header bottle ,and also no sign of coolant being sucked by the pump when the engine was revved ...the temp gauge was shooting up rather quickly on the digital read so I decided to turn her off...

So far I have taken the prt thermostat off and tested that with a kettle full of hot water which seemed to be functioning ok , so now im either thinking of massive air lock as I cant undo the bleed screw but the heater is getting hot which is confusing or maybe it could be the coolant pump has had it ?? any ideas very much appreciated....

T-Cut · 21st August 2015, 17:53

The heater matrix wouldn't get hot if the water pump had failed. An air lock would be the logical culprit considering your report. Having said that I've never yet used the bleed valve and haven't had any problems with air locking. The small bore pipe from the head/manifold to the header tank filler neck is the head air bleed. Obviously if that's blocked, the head may not vent fully. Try poking through the hole in the neck. This is where they tend to block. Also blow down the pipe while it's disconnected to confirm the vent valve to the head is clear.

TC

SD1too · 21st August 2015, 19:22

Just a couple of points to add to T-Cut's reply:

Quote:

Originally Posted by bear-mg

... I could hear the water pump which sounded like the bearings were a little noisy ..

How did you hear this noise? Worn water pump bearings are only usually detectable by placing the tip of a screwdriver on the housing and the handle touching your ear. Can you do this on the 1.8 engine?

Quote:

... rad cap was of to bleed any air out as unfortunately I couldn't undo the bleed screw as it felt like it was going to snap ...

In which case you need to renew that hose/bleed screw assembly. Failing to follow MGR's filling and bleeding procedure has been the cause of many members' cars' overheating problems. Here it is.

Your pump won't be the problem.

Simon

bear-mg · 21st August 2015, 19:41

A little update , just been in the garage and managed to get the bleed screw open by gently applying some heat from my mini blow torch , bled the system again and started her up , i also noticed that despite the digital temp display showing over 90 degrees the small return pipe from the inlet manifold to the header tank felt cool ..could this be a blocked jiggle valve? i switched the engine off and let it cool a little , took the small return pipe off the header tank and blew down it which resulted in the water over flowing from the tank...

once again heater nice and hot , which as t-cut said must mean pump is actually ok...

T-Cut · 21st August 2015, 20:11

Quote:

Originally Posted by bear-mg

- - - despite the digital temp display showing over 90 degrees the small return pipe from the inlet manifold to the header tank felt cool ..could this be a blocked jiggle valve?

No, that's nothing to worry about. Once the pressure cap is in place, the small inlet on the neck is blanked off. The primary purpose of the pipe is to allow trapped air in the head to bleed out while the cap is off during the refill. Obviously the jiggle valve in the manifold has to be clear so it works during the refill/bleed operation. Under normal running conditions it's impossible for coolant to 'circulate' via this pipe.

TC

bear-mg · 21st August 2015, 20:40

in theory then the jiggle valve is ok? nothing was returning from it with the engine running and cap off, im guessing this means there is no air in the system.. just worried why the temp gauge rises quite quickly ,what should the digital temp gauge read at operating temp , should it be around 88 degrees ?

T-Cut · 21st August 2015, 21:51

The head vent can be checked by blowing down the small pipe as I noted earlier. Providing it blows through it's OK.

My digi gauge reads 90-91C most of the time. The original PRTs are rated 88C. These give running temperatures of around 90-100C for the petrol engines, but there are variations in the pressure rating which also affects running temperature. You may have an after market 82C one, which will give a correspondingly lower running temperature. A running temperature of 88C would be considered a bit low for the 1.8T. But it also depends wheher your temperature gauge is actually measuring the head temperature. If it has a thermocouple probe somewhere on the pipework, it will read lower than the OBD readout.

The 1.8 engines warm up very quickly.They only have around six litres of coolant.

TC

bear-mg · 21st August 2015, 22:32

thanks for the info...what temp should the fan cut in, i'm guessing just over 100 degrees for the low speed? just been out in the garage again and after switching the engine off I could hear a hissing sound like pressure escaping ,sounded like it was coming from the header cap , I've ordered some new Viton seals so hopefully that will help it maintain pressure ...

bear-mg · 21st August 2015, 22:45

just found this info on another forum...

Engine Running
With the engine running, the cooling fan can operate at either high or low speed, depending on engine coolant temperature. If the ECT sensor registers a temperature of between 98 °C and 104 °C, the ECM (C0913) energises the low fan speed relay within the cooling fan assembly (COO88) on a U wire. The energised low fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire!

If the ECT sensor registers a temperature of between 105 °C and 112 °C, the ECM (C0913) energises the high fan speed relay within the cooling fan assembly (COO19) on a U/R wire. The energised high fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire

The ECMswitches both cooling fan relays off if the ECT sensor registers a temperature of 98 °C or lower

SD1too · 21st August 2015, 23:14

That document is not written very well. Your low speed should cut-in at 104° and stop when the coolant temperature falls to 98°.

Simon

21st August 2015, 16:36	#1
bear-mg Loves to post mg zt cdti 160👍 Join Date: Jun 2014 Location: bath Posts: 374 Thanks: 105 Thanked 50 Times in 43 Posts	suspected coolant pump I managed to finally get around to refitting my rebuilt turbo to the zt , started the old girl up , she was slightly reluctant at first as she has been sat for nearly a year so the previous owner tells me ...all was going well , the old oil residue in the exhaust was burning off nicely , I noticed the I could hear the water pump which sounded like the bearings were a little noisy , I had the dash set to number 7 on the obd function so I could keep an eye on the coolant temp , rad cap was of to bleed any air out as unfortunately I couldn't undo the bleed screw as it felt like it was going to snap ...i left it running for a while with the rad cap off , then put the cap on ,which made the temp shoot up .....before i put the cap on I couldn't see any coolant coming out of the small return pipe to the header bottle ,and also no sign of coolant being sucked by the pump when the engine was revved ...the temp gauge was shooting up rather quickly on the digital read so I decided to turn her off... So far I have taken the prt thermostat off and tested that with a kettle full of hot water which seemed to be functioning ok , so now im either thinking of massive air lock as I cant undo the bleed screw but the heater is getting hot which is confusing or maybe it could be the coolant pump has had it ?? any ideas very much appreciated.... Last edited by bear-mg; 21st August 2015 at 16:39..

21st August 2015, 17:53	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	The heater matrix wouldn't get hot if the water pump had failed. An air lock would be the logical culprit considering your report. Having said that I've never yet used the bleed valve and haven't had any problems with air locking. The small bore pipe from the head/manifold to the header tank filler neck is the head air bleed. Obviously if that's blocked, the head may not vent fully. Try poking through the hole in the neck. This is where they tend to block. Also blow down the pipe while it's disconnected to confirm the vent valve to the head is clear. TC Last edited by T-Cut; 21st August 2015 at 18:09.. Reason: Fix typos

21st August 2015, 19:41	#4
bear-mg Loves to post mg zt cdti 160👍 Join Date: Jun 2014 Location: bath Posts: 374 Thanks: 105 Thanked 50 Times in 43 Posts	A little update , just been in the garage and managed to get the bleed screw open by gently applying some heat from my mini blow torch , bled the system again and started her up , i also noticed that despite the digital temp display showing over 90 degrees the small return pipe from the inlet manifold to the header tank felt cool ..could this be a blocked jiggle valve? i switched the engine off and let it cool a little , took the small return pipe off the header tank and blew down it which resulted in the water over flowing from the tank... once again heater nice and hot , which as t-cut said must mean pump is actually ok... Last edited by bear-mg; 21st August 2015 at 19:46..

21st August 2015, 23:14	#10
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,485 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	That document is not written very well. Your low speed should cut-in at 104° and stop when the coolant temperature falls to 98°. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

21st August 2015, 20:40	#6
bear-mg Loves to post mg zt cdti 160👍 Join Date: Jun 2014 Location: bath Posts: 374 Thanks: 105 Thanked 50 Times in 43 Posts	in theory then the jiggle valve is ok? nothing was returning from it with the engine running and cap off, im guessing this means there is no air in the system.. just worried why the temp gauge rises quite quickly ,what should the digital temp gauge read at operating temp , should it be around 88 degrees ?

21st August 2015, 21:51	#7
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	The head vent can be checked by blowing down the small pipe as I noted earlier. Providing it blows through it's OK. My digi gauge reads 90-91C most of the time. The original PRTs are rated 88C. These give running temperatures of around 90-100C for the petrol engines, but there are variations in the pressure rating which also affects running temperature. You may have an after market 82C one, which will give a correspondingly lower running temperature. A running temperature of 88C would be considered a bit low for the 1.8T. But it also depends wheher your temperature gauge is actually measuring the head temperature. If it has a thermocouple probe somewhere on the pipework, it will read lower than the OBD readout. The 1.8 engines warm up very quickly.They only have around six litres of coolant. TC

21st August 2015, 22:32	#8
bear-mg Loves to post mg zt cdti 160👍 Join Date: Jun 2014 Location: bath Posts: 374 Thanks: 105 Thanked 50 Times in 43 Posts	thanks for the info...what temp should the fan cut in, i'm guessing just over 100 degrees for the low speed? just been out in the garage again and after switching the engine off I could hear a hissing sound like pressure escaping ,sounded like it was coming from the header cap , I've ordered some new Viton seals so hopefully that will help it maintain pressure ...

21st August 2015, 22:45	#9
bear-mg Loves to post mg zt cdti 160👍 Join Date: Jun 2014 Location: bath Posts: 374 Thanks: 105 Thanked 50 Times in 43 Posts	just found this info on another forum... Engine Running With the engine running, the cooling fan can operate at either high or low speed, depending on engine coolant temperature. If the ECT sensor registers a temperature of between 98 °C and 104 °C, the ECM (C0913) energises the low fan speed relay within the cooling fan assembly (COO88) on a U wire. The energised low fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire! If the ECT sensor registers a temperature of between 105 °C and 112 °C, the ECM (C0913) energises the high fan speed relay within the cooling fan assembly (COO19) on a U/R wire. The energised high fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire The ECMswitches both cooling fan relays off if the ECT sensor registers a temperature of 98 °C or lower