740 hose to heat exchange pops off

Jessica 740 · Sep 30th, 2012, 22:24

This first happened a year ago....was driving my 740 (GLE auto 1990) fast and the car overheated. Pulled over and realised the hose to the heat exchange had come off, no water left in expansion tank so put lots in and she was fine. The same thing happened again a couple of weeks ago but white smoke came out of the exhaust and the engine made a loud ticking noise. There was some oily water on the floor under the engine. The AA man put lots of water in, she seemed to be running fine but he said there was still a lot of pressure in the engine. My garage said the same about pressure in the engine (the hose from the radiator to the head is not squashy - sorry I can't find a better way of describing that). Since then she has been running really well but I haven't gone over 40 mph. She has been losing water - has needed lots put in the reservoir, but it hasn't been leaking onto the floor under the engine. Today I drove fast and the hose popped off off -we stopped quickly and put lots of water in and she was fine.
Does anyone have any thoughts as to why there is pressure which is causing the hose to pop off, and if the water loss sounds like the early stages of head gasket failure or something else?

I have been Googling this but getting nothing and everything as an answer.
Any suggestions would be extremely welcome. The car is due tax (tomorrow!) and MOT. We've had her for 5 years and she's been excellent but I don't want to do the MOT if it's going to be really expensive to fix this overheating problem.
Thank you very much in advance.

mikealder · Sep 30th, 2012, 22:30

If your lucky it's the head gasket, if not the engine is shot, might be time to take a closer look as to what is going wrong inside the engine - Mike

brodgar · Sep 30th, 2012, 22:48

it is possible that there is a headgasketproblem where the water enters the combustionchamber.
the waterchannel is close to an inletcanal and so the water goes into the
combustionchamber.

therefore you will not find a waterleak to anywhere to the outside of the car,
nor does the water leak into the oilsump.

if you rev the engine hard and get the exhaustgas analysed/metered
it will give you a clue.

============
in the end nothing else will do than take the head off and take a look.

brodgar · Oct 4th, 2012, 18:58

small adjustment.

take the I N L E T - manifold off, that is most likely where the gasket is leaking.

that is\a small job= about 1 1/2 hours and not to costly.

do that before you take the head off

Steve940estate · Oct 4th, 2012, 19:30

I'm surprised the garage couldn't offer a proper reason for the loss of water.
If the car has run OK for a year the I would be surprised if the head gasket was the original fault. Normally once the gasket fails you will have other problems like poor starting from cold or white/grey smoke. This is down to the coolant getting inside the engine.

The original fault where the hose popped off might have been down to something simple like the thermostat staying shut. The engine will then overheat and the excess pressure created will find the easiest way to escape. In your case it might have been a slightly loose hose. The cooling system will be pressurised when everything is OK it's the excess pressure that causes a problem. The fact that the same hose has come off might indicate a problem there.

The trouble is that now it's happened again the headgasket might have failed. If you remove the spark plugs their condition will indicate what is going on. Do them one at a time so you know where the problem is. If they are all the same and look OK you need to find the leak. There are a few likely places. if there are no signs of a leak under the bonnet it might be the heater inside the car that is leaking. Check the carpets.

There's a few ideas, hope you can sort it out.

baggy798 · Oct 4th, 2012, 23:28

I would have a go at replacing the coolant filler cap and thermostat. The cap is the thing that regulates the pressure in the system, and if it fails the pressure will just build up and up.

I think when the thermostat fails the engine can overheat, but I don't know if it increases the system pressure drastically when it does that.

Part numbers:
9445462 - Filler Cap (green, 150kPa) - £14.64
273459 - Thermostat (87c) - £17.04

They are tough engines and you might get lucky with the head gasket too. A hose started leaking on my car and it ran really low on water (~2 litres) for quite a few miles at speed before noticing (stupid compensated water temp gauge!). Replaced hose and topped up and so far so good (touch wood!).

Jessica 740 · Oct 5th, 2012, 00:26

Thank you all very much for your advice. I really don't want to lose this car but don't have loads of cash to throw at the garage so it is really appreciated. We've been scouring ebay & autotrader over the last few days, quite depressing, no 740's left. Anyway, thank you for your suggestions and I will report back after the weekend (husband being sent under the bonnet).

Sep 30th, 2012, 22:24	#1
Jessica 740 New Member Last Online: Oct 15th, 2012 15:20 Join Date: Aug 2009 Location: London	740 hose to heat exchange pops off This first happened a year ago....was driving my 740 (GLE auto 1990) fast and the car overheated. Pulled over and realised the hose to the heat exchange had come off, no water left in expansion tank so put lots in and she was fine. The same thing happened again a couple of weeks ago but white smoke came out of the exhaust and the engine made a loud ticking noise. There was some oily water on the floor under the engine. The AA man put lots of water in, she seemed to be running fine but he said there was still a lot of pressure in the engine. My garage said the same about pressure in the engine (the hose from the radiator to the head is not squashy - sorry I can't find a better way of describing that). Since then she has been running really well but I haven't gone over 40 mph. She has been losing water - has needed lots put in the reservoir, but it hasn't been leaking onto the floor under the engine. Today I drove fast and the hose popped off off -we stopped quickly and put lots of water in and she was fine. Does anyone have any thoughts as to why there is pressure which is causing the hose to pop off, and if the water loss sounds like the early stages of head gasket failure or something else? I have been Googling this but getting nothing and everything as an answer. Any suggestions would be extremely welcome. The car is due tax (tomorrow!) and MOT. We've had her for 5 years and she's been excellent but I don't want to do the MOT if it's going to be really expensive to fix this overheating problem. Thank you very much in advance.

Sep 30th, 2012, 22:48	#3
brodgar I've Been Banned Last Online: Nov 27th, 2012 10:56 Join Date: Feb 2009 Location: Forest Row	water loss it is possible that there is a headgasketproblem where the water enters the combustionchamber. the waterchannel is close to an inletcanal and so the water goes into the combustionchamber. therefore you will not find a waterleak to anywhere to the outside of the car, nor does the water leak into the oilsump. if you rev the engine hard and get the exhaustgas analysed/metered it will give you a clue. ============ in the end nothing else will do than take the head off and take a look.

Oct 4th, 2012, 18:58	#4
brodgar I've Been Banned Last Online: Nov 27th, 2012 10:56 Join Date: Feb 2009 Location: Forest Row	E r r a t u m small adjustment. take the I N L E T - manifold off, that is most likely where the gasket is leaking. that is\a small job= about 1 1/2 hours and not to costly. do that before you take the head off

Sep 30th, 2012, 22:30	#2
mikealder VOC Member Last Online: Nov 6th, 2016 10:18 Join Date: May 2009 Location: Blackpool UK	If your lucky it's the head gasket, if not the engine is shot, might be time to take a closer look as to what is going wrong inside the engine - Mike

Oct 4th, 2012, 19:30	#5
Steve940estate Steam Driven PC Owner. Last Online: Mar 4th, 2024 23:50 Join Date: Dec 2004 Location: Not sure.	I'm surprised the garage couldn't offer a proper reason for the loss of water. If the car has run OK for a year the I would be surprised if the head gasket was the original fault. Normally once the gasket fails you will have other problems like poor starting from cold or white/grey smoke. This is down to the coolant getting inside the engine. The original fault where the hose popped off might have been down to something simple like the thermostat staying shut. The engine will then overheat and the excess pressure created will find the easiest way to escape. In your case it might have been a slightly loose hose. The cooling system will be pressurised when everything is OK it's the excess pressure that causes a problem. The fact that the same hose has come off might indicate a problem there. The trouble is that now it's happened again the headgasket might have failed. If you remove the spark plugs their condition will indicate what is going on. Do them one at a time so you know where the problem is. If they are all the same and look OK you need to find the leak. There are a few likely places. if there are no signs of a leak under the bonnet it might be the heater inside the car that is leaking. Check the carpets. There's a few ideas, hope you can sort it out.

Oct 4th, 2012, 23:28	#6
baggy798 🤍💙💗 Last Online: Today 02:46 Join Date: Mar 2006 Location: Lichfield	I would have a go at replacing the coolant filler cap and thermostat. The cap is the thing that regulates the pressure in the system, and if it fails the pressure will just build up and up. I think when the thermostat fails the engine can overheat, but I don't know if it increases the system pressure drastically when it does that. Part numbers: 9445462 - Filler Cap (green, 150kPa) - £14.64 273459 - Thermostat (87c) - £17.04 They are tough engines and you might get lucky with the head gasket too. A hose started leaking on my car and it ran really low on water (~2 litres) for quite a few miles at speed before noticing (stupid compensated water temp gauge!). Replaced hose and topped up and so far so good (touch wood!).

Oct 5th, 2012, 00:26	#7
Jessica 740 New Member Last Online: Oct 15th, 2012 15:20 Join Date: Aug 2009 Location: London	Thank you all very much for your advice. I really don't want to lose this car but don't have loads of cash to throw at the garage so it is really appreciated. We've been scouring ebay & autotrader over the last few days, quite depressing, no 740's left. Anyway, thank you for your suggestions and I will report back after the weekend (husband being sent under the bonnet).

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