Can lpg cause overheating

Hi,

Thanks for such a good forum and for my first real post, here goes:

My 3.9 LPG Discovery overheats (I bought it about 2 weeks ago that way), sometimes just hot with no water loss and other times red light and dumps the water. Sometimes the temp drops back to normal and sometimes not. Sometimes 500 yds sometimes 30 miles.

Compression test is good - 175 best 165 worst on all 8 cylinders.

My thoughts are leading me towards the cooling side, but rad is ok, new water pump, top hose & expansion vessel.

Only thing left is the LPG and the way its plumbed in.

Has anyone had issues with the LPG causing overheating.

Thanks

Dave

Could be a fault in the vapouriser

Try running on petrol only, if no overheat problems then it would point to your lpg

Thanks Deasy,

Good idea, I'll remove the LPG heating pipework and put it back to standard and if no overheating then look at the LPG further.

Just some times you need to put pen to paper and ask for help to see your next step.

Dave

Can you not just switch it off? I can on mine??

Yes, but its the way they have run the heating pipework i'm wondering.

They have tee'd in to the heater connections on the flow & return after the metal pipework and the two hoses rise behind the engine then drop to the vapouriser then rise to botom connections. With no bleed points. The hoses are higher than the radiator.

I just see air locks? Hence causing the overheating?.

radiator hot all over?

Hi Sassanach,

Yes, hot all over. The hot water moved down the headder then across the tubes.

Since then, I took some other advice and yesterday went to my local MOT garage and he put the sniffer in the header tank and yes the reading rose, we stopped it at 2150 ppm. So head gasket failure or simalar.

I asked Kev if any of these pour in cures work. He said he had used K-seal and it lasted 20k miles. So today in some went.

I tried it tonight and, so far no problems, but as they say tomorrow's another day.

A faulty vaporiser can mimic hg failure

Hope you get sorted mate, I'm still waiting to get mine back from the garage!

I was gonna put HGF on last night but didnt wanna depress you lol. check the liners have not slipped when the heads are off or you are wasting your time.

kseal can work but normally it lets you down when you most need it like in the snow when it blew the top hose and then a week later the heater matrix on my old 4 door.

if you only had slight water consumption or weeping core plugs I would say k seal but not for pressurising and pushing water out

Fett LOL.

Kseal worked for about 10 miles, but once I accelorated above 2000 rpm, then up the temp went.

My wife has gone tangental and wants it sold (money pit etc etc). I said, next step heads off, if it looks ok then replace gaskets if look for an engine.

So.. this week, heads off, but can you tell when a liner has dropped? Is it noticable or is it only part of a mill?

yeah you can see it will be lower than the rest of the top of the block. it doesnt have to be much either I mean only a fraction more than nothing lol.

If you bung some pics on then we can have a look, fanatic is normally good at spotting it from pics.

How much did you pay and whats the rest of the car like? You have to be sure its worth all this before you get in too deep

Thanks, the rest is fine. Underneath is solid, no plates; only minor bits needed, like sunroof seal (found that out on saturday and today - but thats another story), gear bias plate, slight repair needed to drivers seat, etc.

For a 1999 / 2000 its in good condition. To be fair when I bought it I was prepared to put a new engine in it, just nothing seemed to point towards that.

What got to Bridget was when we took the Disco out an it overheated, the LPG vapouriser lost its water along with the heater and must have had some liquid LPG in the supply pipe. So when we stopped to refill the radiator, it vapourised the LPG, it blew the filter apart. We had a house fire back in 1996, and ever since then, we have both been very concious of burning smells etc. And this was the icing on the cake so to speak.

My attitude is one step at a time. Cars are not malicious, just pains in the a**e. So rule out things one at a time until you crack it.

To answer you original Q - can LPG cause overheating? They consensus of opinion is that LPG tends to burn hotter than petrol and has less of a cooling effect, so therefore, yes there is a tendency towards overheating.

however others do disagree - Go LPG Research - VSR

My wife's old alpha 156 would overheat, dump the water then run ok for ages. Then the temp gauge would go up, then down then up etc. in the end it turned out to be the head gasket. Had the head skimmed and fitted new gaskets. Worked perfectly afterwards

Why dont you just sod the lpg off (for the time being if you insist ) and then get it sorted on petrol first? just to simplify the issue...

Hi Mr Noisy, that sounds about right , that was my thoughts.

Since then, things have moved on..

I have removed the heads and here are some pics

http://img849.imageshack.us/img849/8742/imag0005au.jpg
http://img69.imageshack.us/img69/6182/imag0014pq.jpg
http://img812.imageshack.us/img812/5617/imag0010xk.jpg
http://img253.imageshack.us/img253/2820/imag0009kj.jpg
http://img341.imageshack.us/img341/7659/imag0007ol.jpg

Dont worry about the fluid in the cylinders, its deisel; to see if the rings are worn.

The best pic is 0005. This is No 2 cylinder on the LH bank. The piston is a different colour to the other 7.

There is a very slight lip inside the bore - only about .5 mm. Is this enough to cause the overheating.

Any advice will be apreciated.

Dunno about the lip, but the discolouration looks like that cylinder is running leaner (therefore hotter) than the others .. dunno how you'd cure it, mind!

Thanks Paul,

If you look at the head gasket there is no sign of any kind of seepage / leakage on either side.

Hmmm, definitely a problem there if that cylinder is odd.

What does the spark plug say for that cylinder?

Again, if it is taking water into that cylinder it can cause this cleaning effect, basically steam cleaning the piston.

Couple of things with the hot water piping to the vapouriser: If you take the feed from the top of the engine and go directly to the vapouriser, then from the vapouriser to the heater and then heater back to the lower inlet on the engine, you will save lots of water joints and T pieces, and potential leaks.

It also means that the hot water gets to the vapouriser first, and an air lock in the vapouriser is almost impossible.

Done it on ours a couple of years ago and it works a treat.

Don't use Britpart or Allmakes gasket sets etc, buy a Victor Reintz gasket set, that will ensure that the valve stem seals will actually fit, and they are excellent quality. Buy genuine head bolts.

When you re-assemble, fit the heads onto the blocks and with locating dowels engaged. Then put four bolts in, two at each end and tighten to something light, about 5lb ft or so.

Fit the inlet manifold with the old gasket and fit a bolt at each corner and nip up tight.

That ensures that the heads are aligned with the inlet manifold faces. If you notice, there is a fair bit of wobble allowed on the dowels, locating the heads this way means you are sure that they are in line while you tighten the heads down.

We've done 50k miles on lpg with no major problems, but we did have the start of a head gasket leak on one bank, and found the heads not as tight as expected, so new Reintz gaskets and genuine bolts were fitted.

Good luck!

Peter