Anyone know anything about cars?

Bluelass · March 16, 2008

Right, here's the situation -

Plenty of water in radiator but engine running cold for several miles then heating up to above normal temp for a short while (minutes at most) then returning to normal temp (100 C ish).

Radiator cap and top hose cold to the touch even after running engine which leads me to believe that there's air in the system somewhere. Loosen radiator cap and air vents off (so I was right) but start up again from cold and the same thing happens.
So, air is getting in the system somewhere - there's no leaks in terms of water escaping but air must be being drawn in somewhere.
My brain doesnt want to even think about this but could it be the head gasket? If hoses leak is it possible that they could draw in air? My limited knowledge of physics would say that a leaking hose would push out fluid due to the internal pressure of the system but I may be wrong.

I've looked for the other signs of head gasket trouble - gooey stuff by oil filler cap and reduced performance etc but no signs of that.

The vehicle is a Jeep Grand Cherokee 4.7lt V8 that runs on LPG but because the gas only flicks on when it gets to a certain temp I'm useing too much petrol at the moment!

Any ideas?

Vim Fuego · March 16, 2008

Could it be a thermostat problem ? Have you tried running the engine to a point where the thermo switch kicks in ? Also, try your internal heating system is working properly, probably not related but you never know, sorry i can't be more help than that.

Vim Fuego · March 16, 2008

Or maybe try this ...

" The air flap when the engine is cold moves to direct warm air (collected from around the exhaust) into the engine to help it run more smoothly. When the engine is warm the flap reverts to supplying cold air from behind the grill area. To test the flap disconnect the hose (3) from the airbox and suck on the end. You should see/feel/hear the flap in the air box move. You shouldn’t be able to suck air easily through the pipe, if you can then there is a fault with the air flap (uncommon). In my experience even if the flap is seized it doesn’t affect the running of the car at all when warm and only marginally when cold."

heatmeiser · March 16, 2008

I put water where the oil should go once. I'm clearly not the man to ask.

Bluelass · March 16, 2008

The heating system is blowing cold air until the engine warms which I suppose is fairly normal - it's the fact that it takes so long to heat up which is the issue.
Anyway, will take it to the garage where I usually take it tomorrow - the guy who owns it is James Vaughan's great uncle (probably doesnt make him a better mechanic but at least we can talk about Vaughany and the Blues)

I have a bad feeling that it's going to be a gasket and although I love my Jeep, they do cost a lot when things go wrong. Having said that, I only pay 47p a litre for lpg so I suppose it's swings and roundabouts.

Rook · March 16, 2008

If its the head gasket you should white smoke coming from your engine while driving. I don't think you'd be going anywhere either. I recently had the same problem with my car. It could just be the H20 pump isn't working and needs replaced. About a 300 repair unless the water pump is hard to get to.

H20 pump - $50-100

Flush and fill - $100-120

Labor - depending on where its at.

Hoses - if you need new hoses that's when it could get expensive.

Bluelass · March 16, 2008

Rook said:
If its the head gasket you should white smoke coming from your engine while driving. I don't think you'd be going anywhere either. I recently had the same problem with my car. It could just be the H20 pump isn't working and needs replaced. About a 300 repair unless the water pump is hard to get to.

H20 pump - $50-100

Flush and fill - $100-120

Labor - depending on where its at.

Hoses - if you need new hoses that's when it could get expensive.

Checked for white smoke, none. Have driven 15 miles to hospital and back at a calm 55/60mph and seems to be performing okay (fingers crossing furiously) and will check oil, water, smoke, heater, leaks, mirror, signal, manouvre. Oops, got carried away then.
Thanks for the advice. (y)

When I had a Ford Escort Mk 1 I used to do all my own basic stuff, oil, air filter, brakes etc but when I lift the bonnet on this thing it's well scary. Don't even know where the oil filter is there's so much stuff under there! :unsure:

monty · March 17, 2008

Bluelass said:
Checked for white smoke, none. Have driven 15 miles to hospital and back at a calm 55/60mph and seems to be performing okay (fingers crossing furiously) and will check oil, water, smoke, heater, leaks, mirror, signal, manouvre. Oops, got carried away then.
Thanks for the advice.
When I had a Ford Escort Mk 1 I used to do all my own basic stuff, oil, air filter, brakes etc but when I lift the bonnet on this thing it's well scary. Don't even know where the oil filter is there's so much stuff under there!

If the head gasket has gone then you will find that your oil dip stick will have emulsified oil on it, ie turning white. I suspect that Vim has it right and your thermostat is buggered Lass so get it to the garage before you do blow the head (y)

Chris · March 17, 2008

I'd change the thermostat. Only cost a couple of quid. If the rad has water in it but even when the engine has been running for a while the heater is still blowing cold, then I'd be 98% certain that the thermostat had gone which is not uncommon.

You might alternatively have an air lock caused by build up of sludge in the engine. Only way to find out is to drain the water system and run a flush through and then refill it.

Good luck

I hate cars that don't behave. Let us know what it was.

Bluelass · March 17, 2008

the oil is clean, the filler cap gunge free and the dipstick okay too. Heater now working normally. Perhaps it was an airlock which I released when I opened the radiator cap. Who knows!
Been driving very carefully anyway, not razzing (I never do anyway but it's a temptation at times in such a big monster of a car) so barely touching 2000 revs, no strain on the engine at all.

It's behaved itself today, been to work and back (22 miles) and hospital and back 30 miles. I'm off weds and thurs so will take it in then. Need the car to get to the match on saturday so it must be fixed!
Thanks guys for your advice. (y)

And thank you especially for not saying 'have you put water in it, love' with a patronising smirk......!!!!

evertonianstu · March 17, 2008

It may or may not help you to hear that i have absolutely no idea about cars.

SuitsBlue · March 17, 2008

Bluelass said:
the oil is clean, the filler cap gunge free and the dipstick okay too. Heater now working normally. Perhaps it was an airlock which I released when I opened the radiator cap. Who knows!
Been driving very carefully anyway, not razzing (I never do anyway but it's a temptation at times in such a big monster of a car) so barely touching 2000 revs, no strain on the engine at all.

It's behaved itself today, been to work and back (22 miles) and hospital and back 30 miles. I'm off weds and thurs so will take it in then. Need the car to get to the match on saturday so it must be fixed!
Thanks guys for your advice.
And thank you especially for not saying 'have you put water in it, love' with a patronising smirk......!!!!

maybe its haunted, and mentioning it here has exorcised the demon.

what car is it again?

Vim Fuego · March 17, 2008

Buy fluffy dice for the rear view mirror, cars always go faster when they have fluffy dice,FACT.

Bluelass · March 17, 2008

It's a Jeep Grand Cherokee 4.7lt V8 which runs on lpg, I could never afford the petrol.....and there's no fluffy dice just an Everton sticker and a dog guard in the back.

I suppose I could get Blue and white fluffy dice if it helped.