Temp warning Problem Facelift ZT 190

CMPQS · 28th September 2007, 08:06

On the way home last night & the engine overheat message came on for a couple of seconds & the temp gauge shot up from its normal position so the red light came on. Dashed to the side of the road ASAP but before I got there everything went back to normal. Popped the bonnet & checked coolant & oil for dreaded HGF & everything is OK. Plenty of water & no mayo.

Due for a service next Friday so was going to get them to check it out.

However it happened again this morning on the way in to work. Water level & oil condition as last night.

Anyone had this problem before? Got any ideas as to why its happening?

I have no other electrical gremlins & plenums were checked a couple of weeks ago by me & were fine, totally clear in fact.

Theories Anyone??

Greeners · 28th September 2007, 08:18

If it happens again, check the fans and guage. If the ECU fails to get an input, it will run the fans and drop the needle of the guage back to the rest which is lower then if the engine was stone cold.

Most likely to be the temperature sensor or wrining from the sensor.

David3807 · 28th September 2007, 08:59

Suggestions:

1/ Thermostat sticking.

2/ Engine cooling fan failed.

3/ Possible air in the co0ling system although that would raise the question where did it come from.

Would be helpful to know the traffic conditions, your speed etc when it happened. What was the cooling fan doing during the overheat ??

Not sure about the temp sensor as if it fails and gives no signal the gauge should fall back to stone cold and the fan should run at top speed. You mention that the gauge shot up so not sure.

Would put HGF right at the bottom of the possibles list cos its pretty unusual on a KV6.

Greeners · 28th September 2007, 09:08

Quote:

Originally Posted by David3807

Not sure about the temp sensor as if it fails and gives no signal the gauge should fall back to stone cold and the fan should run at top speed. You mention that the gauge shot up so not sure.

That description is out of the engine management manual for "loss of input" from the sensor

CMPQS · 28th September 2007, 09:57

Thanks guys.

more info.

Air con on econ mode & travelling on a duel carrigeway doing 60 - 70 mph in both instances. Less than 5 miles travelled. gauge behaved as usual in getting to normal operating temp.

The gauge itself only moved up after the warning had come on & it moved up very quickly stayed at the top of the gauge for approx 3 or 4 seconds & dropped back down neraly as quickly as it went up.

Once I had determined that all seemed to be well again & I had completed my journey I sat with the car idling listening to the fan to make sure this was working as should. Left her running for 15 minutes but the gauge never budged.

I am hoping a dodgy connection or wiring. If this is the case would it effect bothe the gauge & the electronic message?

Perhaps a sticking thermostat is more likely?

kaiser · 28th September 2007, 14:00

The best advice,apart from finding the problem, is to make very sure that your water level is OK. As a rule, there should be absolutely no water drop, and any such drop constitutes a problem to be taken very seriously indeed for the following reasons.
I had exactly the same symptoms, and that turned out to be a loose sleeve, resulting in HGF. I think that by the time you see the temperature gauge move,it might well be to late!.the gauge is designed to stay on medium, within a broad range of temperatures. Once it moves, which ever way, things are already pretty hot, either hot water or hot air which might well make the needle drop!!!It took a couple of days before mayo started to form under the oil filler cap, but then it started and got worse rather quickly. The engine was taken to pieces and repaired including new belts, but they failed to note the loose liner during this round. Then they took the engine to pieces again, and I received it with small holes in the radiator. It is now with them again, I know the radiator has been fixed and put in, they were supposed to do a test drive and phone me to fetch.They have not phoned and I fear there might still be problems.
I don't want to scare you, but this is a possibility. Also the engines are very prone to air-locks and they tend to form before the thermostat, which means the thermostat is not sensing hot water and won't open. It is therefore important to get rid of the air lock, and I personally think you need a bit of fast road work to get the air moving, leave the heater on full heat to get some flow through early. You will typically hear a noise from the engine as you slow down, and see the water level in the expansion box will have dropped. You will have to do this a couple of times to completely remove the air.
Unless your sensor is faulty, and provided you don't have a leak, it can only be a passage of water internally.
I would get the system pressure tested, very very carefully. And if that is OK, fit new cap on expansion box, test the thermostat very carefully, refill, get rid of air- lock, and monitor the water level like a hawk.
If it still drops, watch for mayo. Any trace of mayo, engine out after having checked for leak in autobox cooler, and in suction vapour pipes.
As an aside, I think it would be prudent to fit a water sensor to the system, so that any drop in the water level will cause an alarm. You have plenty of small possible leaks, which easily will go un-noticed because the engine bay is so stuffed and the undertray, the V and other areas will hinder a flow under the car for all but major problems. The engine runs hot, so there are all chances that the water will evaporate and not give itself away as a puddle on the floor! Checking every day before you use the car is perfect, but it will not warn you regarding a problem developing as you are under way.
I hope you have a small stupid problem. Good luck

28th September 2007, 08:06	#1
CMPQS Avid contributor MG ZT Join Date: Nov 2006 Location: Milton Keynes Posts: 152 Thanks: 0 Thanked 0 Times in 0 Posts	Temp warning Problem Facelift ZT 190 On the way home last night & the engine overheat message came on for a couple of seconds & the temp gauge shot up from its normal position so the red light came on. Dashed to the side of the road ASAP but before I got there everything went back to normal. Popped the bonnet & checked coolant & oil for dreaded HGF & everything is OK. Plenty of water & no mayo. Due for a service next Friday so was going to get them to check it out. However it happened again this morning on the way in to work. Water level & oil condition as last night. Anyone had this problem before? Got any ideas as to why its happening? I have no other electrical gremlins & plenums were checked a couple of weeks ago by me & were fine, totally clear in fact. Theories Anyone??

28th September 2007, 08:18	#2
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	If it happens again, check the fans and guage. If the ECU fails to get an input, it will run the fans and drop the needle of the guage back to the rest which is lower then if the engine was stone cold. Most likely to be the temperature sensor or wrining from the sensor. __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

28th September 2007, 08:59	#3
David3807 Posted a thing or two 2002 R75 Conn SE 2.5l Auto Tourer, 2001 R75 Conn SE 2.5 Auto Saloon Join Date: Nov 2006 Location: Gravesend Posts: 1,897 Thanks: 0 Thanked 2 Times in 2 Posts	Suggestions: 1/ Thermostat sticking. 2/ Engine cooling fan failed. 3/ Possible air in the co0ling system although that would raise the question where did it come from. Would be helpful to know the traffic conditions, your speed etc when it happened. What was the cooling fan doing during the overheat ?? Not sure about the temp sensor as if it fails and gives no signal the gauge should fall back to stone cold and the fan should run at top speed. You mention that the gauge shot up so not sure. Would put HGF right at the bottom of the possibles list cos its pretty unusual on a KV6. Last edited by David3807; 28th September 2007 at 10:52..

28th September 2007, 09:57	#5
CMPQS Avid contributor MG ZT Join Date: Nov 2006 Location: Milton Keynes Posts: 152 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks guys. more info. Air con on econ mode & travelling on a duel carrigeway doing 60 - 70 mph in both instances. Less than 5 miles travelled. gauge behaved as usual in getting to normal operating temp. The gauge itself only moved up after the warning had come on & it moved up very quickly stayed at the top of the gauge for approx 3 or 4 seconds & dropped back down neraly as quickly as it went up. Once I had determined that all seemed to be well again & I had completed my journey I sat with the car idling listening to the fan to make sure this was working as should. Left her running for 15 minutes but the gauge never budged. I am hoping a dodgy connection or wiring. If this is the case would it effect bothe the gauge & the electronic message? Perhaps a sticking thermostat is more likely?

28th September 2007, 14:00	#6
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	The best advice,apart from finding the problem, is to make very sure that your water level is OK. As a rule, there should be absolutely no water drop, and any such drop constitutes a problem to be taken very seriously indeed for the following reasons. I had exactly the same symptoms, and that turned out to be a loose sleeve, resulting in HGF. I think that by the time you see the temperature gauge move,it might well be to late!.the gauge is designed to stay on medium, within a broad range of temperatures. Once it moves, which ever way, things are already pretty hot, either hot water or hot air which might well make the needle drop!!!It took a couple of days before mayo started to form under the oil filler cap, but then it started and got worse rather quickly. The engine was taken to pieces and repaired including new belts, but they failed to note the loose liner during this round. Then they took the engine to pieces again, and I received it with small holes in the radiator. It is now with them again, I know the radiator has been fixed and put in, they were supposed to do a test drive and phone me to fetch.They have not phoned and I fear there might still be problems. I don't want to scare you, but this is a possibility. Also the engines are very prone to air-locks and they tend to form before the thermostat, which means the thermostat is not sensing hot water and won't open. It is therefore important to get rid of the air lock, and I personally think you need a bit of fast road work to get the air moving, leave the heater on full heat to get some flow through early. You will typically hear a noise from the engine as you slow down, and see the water level in the expansion box will have dropped. You will have to do this a couple of times to completely remove the air. Unless your sensor is faulty, and provided you don't have a leak, it can only be a passage of water internally. I would get the system pressure tested, very very carefully. And if that is OK, fit new cap on expansion box, test the thermostat very carefully, refill, get rid of air- lock, and monitor the water level like a hawk. If it still drops, watch for mayo. Any trace of mayo, engine out after having checked for leak in autobox cooler, and in suction vapour pipes. As an aside, I think it would be prudent to fit a water sensor to the system, so that any drop in the water level will cause an alarm. You have plenty of small possible leaks, which easily will go un-noticed because the engine bay is so stuffed and the undertray, the V and other areas will hinder a flow under the car for all but major problems. The engine runs hot, so there are all chances that the water will evaporate and not give itself away as a puddle on the floor! Checking every day before you use the car is perfect, but it will not warn you regarding a problem developing as you are under way. I hope you have a small stupid problem. Good luck