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[feeutfo]

Some mornings, reguardless of weather, I get the engine temp either hesitate or drop during warm up. Once warm no problem.

This showed itself initially with problems running on gas. Miss fires and fuel trim issues etc.

It's taken me a while to notice the two in conjunction, as I hadn't noticed the temp gauge while the LPG was playing up.

When it does play up, the mo is the same. Initial warm up on petrol no problem. Change to gas no problem. Heater gives heat no problem. 2 muns later temp gauge moves off the bottom of the scale, then the issues start on LPG at about 70 degrees engine temp. Turn back to petrol or it will stall and be grumpy.
 Watch the temp gauge hover at 75 then go slowly up to 80. Switch gas on again, stays at 80 for ages, then after that it will heat up to 85 or 90 as normal.

Sometimes it plays up. Sometimes not. But always from cold if it does miss behave. Once warm it's fine all day.

[Entwood]

Sounds to me like the thermostat is opening early and largely .. so allowing a gurt dollop of cold water to circulate, this cools the evaporator down way too much. Then the system heats up again, albeit slowly which is why it all hovers around 75-80.

Reason it is now showing up is cold temperatures making it worse... when warm it made little difference.

Thermostat should open in "bits" as it "regulates" the temperature ... yours is doing it all at once ??

My guess is you will need a thermostat change to sort it.

[Lazydocker]

Sounds like a stat change to me, which I also need to do at some point But I'm trying to hold off and replace the A/C Condenser at the same time as I'll need to remove the Rad for that

IIRC the groomer has always said yours (and mine) seem to run a little cool, not that I'd ever admit he was right

[feeutfo]

Yes it's always wise to deny the Groomer.

I always thought the temp accross my omegas was fairly constant. Which given their age, was probably true.

98k on mine now.

[cem_devecioglu]

Sounds to me like the thermostat is opening early and largely .. so allowing a gurt dollop of cold water to circulate, this cools the evaporator down way too much. Then the system heats up again, albeit slowly which is why it all hovers around 75-80.

Reason it is now showing up is cold temperatures making it worse... when warm it made little difference.

Thermostat should open in "bits" as it "regulates" the temperature ... yours is doing it all at once ??

My guess is you will need a thermostat change to sort it.

 

 
logical..agreed..

[Lazydocker]

Yes it's always wise to deny the Groomer.

I always thought the temp accross my omegas was fairly constant. Which given their age, was probably true.

98k on mine now.

I'm not far behind... Perhaps 10k at most.

[2woody]

Entwood has it about right. Your thermosidiot is just starting to open, so all that cold water sitting in the radiator suddenly enters the system, temporarily cooling it down, before it carries on its temperature rise. Sounds like the thermostat's working pretty ok to me.

You need to raise the switch-over-to LPG threshold temperature a little

[TheBoy]

TBE has a slightly stick stat I think - cruising up the A43 every morning (slowly, as no "enthusism" until fully warmed up), the temp goes above midpoint, then drops dramatically, before rising and settling just below midpoint.

Stat is 2yrs old.

[Andy H]

Two issues here:

1. The thermostat is at the front of the engine and the temperature sender is at the back. When the thermostat first opens a slug of cold water from the radiator flows into the back of the engine and causes a temporary dip in temperature. Once everything is up to temperature the stat maintains 92degrees at the front of the engine (& the gauge reads 85degrees at the back because of the cooler water from the radiator)

2. The return water from the vapouriser gets dumped into the radiator return pipe at the back of the engine when the vapouriser has finished with it. If the vapouriser is cold & frosty that water could be below freezing (further depressing the temperature on the gauge).

The key problem is insufficient flow through the vapouriser (but that doesn't mean that the thermostat isn't faulty too............)

[Entwood]

Two issues here:

1. The thermostat is at the front of the engine and the temperature sender is at the back. When the thermostat first opens a slug of cold water from the radiator flows into the back of the engine and causes a temporary dip in temperature. Once everything is up to temperature the stat maintains 92degrees at the front of the engine (& the gauge reads 85degrees at the back because of the cooler water from the radiator)

2. The return water from the vapouriser gets dumped into the radiator return pipe at the back of the engine when the vapouriser has finished with it. If the vapouriser is cold & frosty that water could be below freezing (further depressing the temperature on the gauge).

The key problem is insufficient flow through the vapouriser (but that doesn't mean that the thermostat isn't faulty too............)

Slight disagreement from me here .... part deux ... The vapouriser return is being dumped into the system from the minute the engine starts, so will actually slow down the rate of warmup of the engine jacket, it won't depress the temperature, although it may stop it rising ..., as to depress the temp the vapouriser water would have to be added "after" the temp had risen .. which it can't do as it is part of the "water jacket"  ....

At least that's how I see it ..

[Andy H]

Two issues here:

1. The thermostat is at the front of the engine and the temperature sender is at the back. When the thermostat first opens a slug of cold water from the radiator flows into the back of the engine and causes a temporary dip in temperature. Once everything is up to temperature the stat maintains 92degrees at the front of the engine (& the gauge reads 85degrees at the back because of the cooler water from the radiator)

2. The return water from the vapouriser gets dumped into the radiator return pipe at the back of the engine when the vapouriser has finished with it. If the vapouriser is cold & frosty that water could be below freezing (further depressing the temperature on the gauge).

The key problem is insufficient flow through the vapouriser (but that doesn't mean that the thermostat isn't faulty too............)

Slight disagreement from me here .... part deux ... The vapouriser return is being dumped into the system from the minute the engine starts, so will actually slow down the rate of warmup of the engine jacket, it won't depress the temperature, although it may stop it rising ..., as to depress the temp the vapouriser water would have to be added "after" the temp had risen .. which it can't do as it is part of the "water jacket"  ....

At least that's how I see it ..

Until you switch to LPG the vapouriser doesn't need any heat. As soon as you start converting liquid to gas there is a big heat demand which causes the drop in temperature.

[Entwood]

Two issues here:

1. The thermostat is at the front of the engine and the temperature sender is at the back. When the thermostat first opens a slug of cold water from the radiator flows into the back of the engine and causes a temporary dip in temperature. Once everything is up to temperature the stat maintains 92degrees at the front of the engine (& the gauge reads 85degrees at the back because of the cooler water from the radiator)

2. The return water from the vapouriser gets dumped into the radiator return pipe at the back of the engine when the vapouriser has finished with it. If the vapouriser is cold & frosty that water could be below freezing (further depressing the temperature on the gauge).

The key problem is insufficient flow through the vapouriser (but that doesn't mean that the thermostat isn't faulty too............)

Slight disagreement from me here .... part deux ... The vapouriser return is being dumped into the system from the minute the engine starts, so will actually slow down the rate of warmup of the engine jacket, it won't depress the temperature, although it may stop it rising ..., as to depress the temp the vapouriser water would have to be added "after" the temp had risen .. which it can't do as it is part of the "water jacket"  ....

At least that's how I see it ..

Until you switch to LPG the vapouriser doesn't need any heat. As soon as you start converting liquid to gas there is a big heat demand which causes the drop in temperature.

ahh different to mine then ... mine starts to take heat from the jacket as soon as the engine starts, then once sufficient heat has been taken to convert the LPG to gas, and the gas pressure rises to whatever the little gizmo is set at, then it auto switches and runs on gas.

[Andy H]

Two issues here:

1. The thermostat is at the front of the engine and the temperature sender is at the back. When the thermostat first opens a slug of cold water from the radiator flows into the back of the engine and causes a temporary dip in temperature. Once everything is up to temperature the stat maintains 92degrees at the front of the engine (& the gauge reads 85degrees at the back because of the cooler water from the radiator)

2. The return water from the vapouriser gets dumped into the radiator return pipe at the back of the engine when the vapouriser has finished with it. If the vapouriser is cold & frosty that water could be below freezing (further depressing the temperature on the gauge).

The key problem is insufficient flow through the vapouriser (but that doesn't mean that the thermostat isn't faulty too............)

Slight disagreement from me here .... part deux ... The vapouriser return is being dumped into the system from the minute the engine starts, so will actually slow down the rate of warmup of the engine jacket, it won't depress the temperature, although it may stop it rising ..., as to depress the temp the vapouriser water would have to be added "after" the temp had risen .. which it can't do as it is part of the "water jacket"  ....

At least that's how I see it ..

Until you switch to LPG the vapouriser doesn't need any heat. As soon as you start converting liquid to gas there is a big heat demand which causes the drop in temperature.

ahh different to mine then ... mine starts to take heat from the jacket as soon as the engine starts, then once sufficient heat has been taken to convert the LPG to gas, and the gas pressure rises to whatever the little gizmo is set at, then it auto switches and runs on gas.

The heat needed to warm up the aluminium casting is tiny compared to the heat need to turn liquid into gas. I wasn't saying that the vapouriser didn't take coolant flow before the engine was warm, I was saying that the full cooling effect didn't kick in until the gas starts flowing.

[feeutfo]

The vap is set in series from the back of the engine block.
Coolant bridge out > vap > hbv > and so on.

So the coolant circulates the vap at all times, if LPG is on or not.

I have never been aware of LPG use cooling the coolant. But for obvious reasons, I have not observed the temp behaviours on petrol only.

On the journey home, the car took a good 15 mins to get up to temp.
Up to about 70 pause, 75 pause. Up to 80 finally, pause. Switch LPG on, gradual rise up to 90, noticed after 20-25 mins after start up that the temp had dropped back to 85.

The LPG switch over threshold has been set at 40c vap temp for about 7months. It's was fine initially, with a very steady decline over that period. As said , initial switch over is fine, and runs well. The danger area seems to be from 65/70c up to 80c on the engine temp gauge.
 Vap temp never drops below 45 once LPG is on, and I saw it at 50 odd for most of this mornings commute. This is ample for vap operation, no?

When working well, LPG used to switch over within 30secs of start up. It now takes a good 5 mins.

It cirtainly sees slow to warm up. Now that I have actually noticed what the temp is doing.

[Entwood]

My moneys on the Stat.... 

It coped in warmer weather .. now its getting cold the system is struggling