Car Heater not working on LPG ML500?

[TechnoWhizz]

Hi All,
2003 W163 ML500 mixfuel. Problem is the car heater isn't working. Fan works, flaps seem to work but mainly cold air, never warm/hot.

Been to Mercland specialists in Nuneaton, Fan and regulator fine, Matrix fine, Hot/Cold valve moving, auxiliary pump replaced (!), Coolant clean and replaced. Engine reaches 80c fine, and doesn't overheat. No loss of coolant.

No improvement.

Runs on LPG (mostly) fine and switches from Petrol->LPG fairly quickly. Only thing is on full acceleration from start, LPG system can't cope and has to be on petrol. Also MPG is about 13

Blame is being laid on LPG system and it's use of the coolant system to heat the LPG fuel, but as they aren't LPG trained they can't touch it.

Tried to speak to the original installer for LPG type so I can get it serviced / checked, but not yet forthcoming.

Any ideas to save me from freezing my bits off? I feel (hope) it's something stupidly simple that's been overlooked......

Cheers Chris

 

[LostKiwi]

How long have you had the car in this configuration (as in with LPG)? Is this your first winter with it?
Has the heater ever worked?

 

[TechnoWhizz]

How long have you had the car in this configuration (as in with LPG)? Is this your first winter with it?
Has the heater ever worked?

Hi,

Yes it's the first winter with it, and the car came fitted with LPG. It's difficult to remember 100% if the heater ever worked as the weather seemed to go from Warm to cold v quickly and I like a cold car climate anyway. Only really noticed it when I needed to clear the screen. However, when I first had the car (June last year), I did check everything was working before I parted with my cash.

I can't understand why it wouldn't work if all the basics are fine, it's not as if a car cooling/heating system is that complicated? (OK so it's MB, but even so?)

 

[LostKiwi]

It does sound like the LPG installation is to blame then unless the heater matrix is blocked (check this first and make sure its been flushed through).

The LPG vapouriser (the bit that converts the liquid propane to a gas before injection into the engine) requires heat to operate. If its not heated it will ice up and fail to work correctly.
The usual way to accomplish this is to plumb it in parallel with the heater circuit. Inspection of the pipework will confirm this.
If the heater flow resistance is greater than the vaporiser more hot water will flow through the vapouriser than the heater, hence no heat.

Easy to check. Find the pipework that goes to the vapouriser and using a pipe clamp restrict the flow. Run the car on petrol and verify if the heater works correctly. If so then we know the issue is with the relative restrictions of the heater and vapouriser. If that is the case there are a few options but it will require some playing around to get right.

1. If the heater is full flow all the time through the heater matrix plumb them in series. If the vapouriser is first it will soak up a fair amount of heat and you may still have only a lukewarm heater. If the heater is first you may not have enough heat left after the heater to stop the vapouriser icing up.
2. Fit a restrictor into the vapouriser feed to balance the flows more evenly. Varying the restrictor will allow tuning of the system to prevent the vapouriser icing.
3. fit a pump in the heater circuit to force water through the heater and effectively reducing the restriction relative to the vapouriser. Its a bit on/off but would probably get around the issue.
The bad news is the heater will never be as effective as a normal car due to the demands of the vaporiser for heat.
You could enhance the whole system with an eternal auxiliary heater but that's significant additional cost.

There is a final (but very costly) option.
There are now LPG systems coming available which don't use a vapouriser and instead inject liquid LPG direct into the engine. These have some benefits in power (the cooling effect of the LPG vapourising in the inlet tract gives a denser charge) and economy. Obviously with a liquid injection system the vapouriser is no longer required so the heating system returns to normal.

 

[TechnoWhizz]

It does sound like the LPG installation is to blame then unless the heater matrix is blocked (check this first and make sure its been flushed through).

The LPG vapouriser (the bit that converts the liquid propane to a gas before injection into the engine) requires heat to operate. If its not heated it will ice up and fail to work correctly.
The usual way to accomplish this is to plumb it in parallel with the heater circuit. Inspection of the pipework will confirm this.
If the heater flow resistance is greater than the vaporiser more hot water will flow through the vapouriser than the heater, hence no heat.

Easy to check. Find the pipework that goes to the vapouriser and using a pipe clamp restrict the flow. Run the car on petrol and verify if the heater works correctly. If so then we know the issue is with the relative restrictions of the heater and vapouriser. If that is the case there are a few options but it will require some playing around to get right.

1. If the heater is full flow all the time through the heater matrix plumb them in series. If the vapouriser is first it will soak up a fair amount of heat and you may still have only a lukewarm heater. If the heater is first you may not have enough heat left after the heater to stop the vapouriser icing up.
2. Fit a restrictor into the vapouriser feed to balance the flows more evenly. Varying the restrictor will allow tuning of the system to prevent the vapouriser icing.
3. fit a pump in the heater circuit to force water through the heater and effectively reducing the restriction relative to the vapouriser. Its a bit on/off but would probably get around the issue.
The bad news is the heater will never be as effective as a normal car due to the demands of the vaporiser for heat.
You could enhance the whole system with an eternal auxiliary heater but that's significant additional cost.

There is a final (but very costly) option.
There are now LPG systems coming available which don't use a vapouriser and instead inject liquid LPG direct into the engine. These have some benefits in power (the cooling effect of the LPG vapourising in the inlet tract gives a denser charge) and economy. Obviously with a liquid injection system the vapouriser is no longer required so the heating system returns to normal.

Many Thanks for all that. Sounds totally logical and I'll go and crimp the pipe tomorrow and see what happens. There is an auxiliary pump as standard on the ML as I got them to change it just in case. I have to admit on the way back, the heater does seem to be trying to send out heat. They did flush the matrix both ways and repoerted it clean, so hopefully, it's a restrictor valve to be fitted and to balance the heating. As long as it clears my screen I don't care!!

 

[television]

You do have 53 the hot/cold change over valve, we do not get much trouble with them

 

[DavidR]

In thermodynamic terms, there will be more than enough heat available for both the heater and the vapouriser, I agree very much with Kiwi above that it is likely there is a plumbing issue. I bet you will find the vapouriser has been fitted in series before the heater matrix, AND is providing a significant restriction to coolant flow, such that it's coolant "outlet" is barely tepid, and hence you have no heater.

Easy way to confirm. Drive the car on petrol. Does the heater then get hot?

 

[Bilal]

Hello i have a very similar problem and am wondering if you solved yours and what the problem was

 

[13enzy]

Hello i have a very similar problem and am wondering if you solved yours and what the problem was

Hi
did you solve your problem ?
how did you do it
any input would be appreciated

 

[Bilal]

Omg yh i solved it and it really is a joke considering the heater works once i disconeccted my vaporizer from the cooling system but once the lpg vape is connected it doesnt....

Thinking that the vaporizer was the problem but lpg mechanic refused to look at it for me or investigate he would only say to me your matrix is blocked but i checked it and it isnt but he was sure it was that and that job on a bmw x3 is a costly one...

Cut the long story short it wasnt the lpg or the heater matrix

This problem really done my head in and cost me money in parts after changing most important componants

It turned out to be the thermostat under my coolant bottle i think they refer to it as a tranny stat its a ****** joke the most cheapest of parts but with the car not overheating you wouldn’t think there was a blockage...

Made me feel like the worse mechanic not solving that and paying someone who just got lucky through investigating and broke the tranny stat whilst taking out the coolant bottle and when they put it back togeather and put a new trans stat on

Bobs your ********* uncle it was fixed....
i hate cars i really do