Overheating v8

Hi im new to the forum.

Ive just bought a Discovery 2 4.0 v8 lpg. Its developed overheating problems, i can drive around all day on petrol and it wont overheat but it will pressurise the cooling system. If you switch over to gas it will overheat instantly, this has been diagnosed as a faulty vapouriser. Its failed a sniffer test and ive done a compression test with 180psi on all cylinders. Ive checked radiator, water pump and put a new thermostat in. Im rather hoping its the head gasket rather than a slipped liner or porous block. Ive also tried k-seal and steel seal to no avail. Any help would be greatly appreciated.

Thanks Shaun

Check the air bleed needle in the header tank isn't blocked. That will stop any air from being removed from the system.

Water pump should really be changed at the same time as the thermostat.

Peter

shaun1987 said:

Hi im new to the forum.

Ive just bought a Discovery 2 4.0 v8 lpg. Its developed overheating problems, i can drive around all day on petrol and it wont overheat but it will pressurise the cooling system. If you switch over to gas it will overheat instantly, this has been diagnosed as a faulty vapouriser. Its failed a sniffer test and ive done a compression test with 180psi on all cylinders. Ive checked radiator, water pump and put a new thermostat in. Im rather hoping its the head gasket rather than a slipped liner or porous block. Ive also tried k-seal and steel seal to no avail. Any help would be greatly appreciated.

Thanks Shaun

Click to expand...

That's good compression - did you have a leak-down test done also? Assuming you have done the obvious checks for exhaust gasses in the coolant, etc. - there is one other often overlooked problem area in a search for otherwise inexplicable overheating and that is a weak or failing oil-pump.

Hi, how could i do a leak down test? I had a sniffer test done on it and it showed that there was combustion gases in the coolant. How could i test the oil pump?

Regards

shaun1987 said:

Hi, how could i do a leak down test? I had a sniffer test done on it and it showed that there was combustion gases in the coolant. How could i test the oil pump?

Regards

Click to expand...

A leak down is similar to a compression test only it determines the rate that compression leaks-down in each cylinder (tells you more about the actual health of each cylinder - ring and valve wise). But now that I see that exhaust gasses are indeed showing-up in your engine coolant - I think you need to have a chat with your mechanic who did the work originally - as you have only 100 miles on it - if I recall correctly? Did he use new stretch bolts, etc.? Did he examine the head gasket area for signs of coolant channeling or anything that might indicate a dropped liner? I would hate to suggest a cracked block as by-far-and-away the most likely LR engine event that causes this is a dropped liner or, if you are really lucky, a faulty head-gasket and/or installation.

BTW - are you getting any codes coming at you (i.e., check engine light on)?

Correction to last - I had assumed you had just had the work done whereas it appears that may not be the case (my apologies as I think I confused you with another member who was having similar problems). A leak-down test will still tell you if the head-gasket has decided to pack-it-in between cylinders.

shaun1987 said:

Hi im new to the forum.

Ive just bought a Discovery 2 4.0 v8 lpg. Its developed overheating problems, i can drive around all day on petrol and it wont overheat but it will pressurise the cooling system. If you switch over to gas it will overheat instantly, this has been diagnosed as a faulty vapouriser. Its failed a sniffer test and ive done a compression test with 180psi on all cylinders. Ive checked radiator, water pump and put a new thermostat in. Im rather hoping its the head gasket rather than a slipped liner or porous block. Ive also tried k-seal and steel seal to no avail. Any help would be greatly appreciated.

Thanks Shaun

Click to expand...

Ignoring the LPG, I would say that's a head gasket although the compression figure might say all O.K. Was there any difference between wet and dry readings on the compression test?

Have you checked the coolant level - do you need to top it up regularly?
Have you tried running with the pressure cap loose? If so is it pumping out water?

The other thing I would suggest is flush your cooling system and get all the sealing gunk out of it or you might cause a problem later. Have you checked your rad isn't blocked?

HTH

Just used it this weekend to tow the caravan to a local site, it drives fine but i do have to top the coolant up once its cooled down enough and theres still alot of pressure in the system, ive ordered the repair kit for the lpg vapouriser so i will be able to see if it works ok on gas.

Regards