Electronic thermostat won't open

[niklos4]

Hello guys...
I'm the owner of an Opel Vectra c 2007 model with a z16xep engine and an LPG conversion (kit by Landirenzo). I had my thermostat replaced few months ago and since then I've experienced almost constant coolant temp of 107 Celsius (no matter the external conditions or driving). The "mechanic" who replaced the stat assured me that this is a normal temp but since then I had at least one busted header tank and a hose so I suspect it's not that "normal" a temperature. I suspected a faulty thermostat and I bought a genuine one and had it replaced. No change in the temp reading whatsoever though(OBD reading real-time with torque app. Analog car instrument indicates 92).
I've made a head gasket test for leaking, flushed the engine block and heat matrix, air bled the system...nothing helps. Recently I noticed that the system behaves the same way (107 Celsius that is) even if I disconnect the plug from the thermostat (it gives a fault code in this way of course) so I suspect that the electronic thermostat is not engaged when it should so it opens only mechanically at about 108 Celsius.
Everything was just fine before I had that thermostat change few months back. I didn't even know where the coolant was in the car and now this....
Any help or ideas would be much appreciated.

[troutybrown]

Hello guys...
I'm the owner of an Opel Vectra c 2007 model with a z16xep engine and an LPG conversion (kit by Landirenzo). I had my thermostat replaced few months ago and since then I've experienced almost constant coolant temp of 107 Celsius (no matter the external conditions or driving). The "mechanic" who replaced the stat assured me that this is a normal temp but since then I had at least one busted header tank and a hose so I suspect it's not that "normal" a temperature. I suspected a faulty thermostat and I bought a genuine one and had it replaced. No change in the temp reading whatsoever though(OBD reading real-time with torque app. Analog car instrument indicates 92).
I've made a head gasket test for leaking, flushed the engine block and heat matrix, air bled the system...nothing helps. Recently I noticed that the system behaves the same way (107 Celsius that is) even if I disconnect the plug from the thermostat (it gives a fault code in this way of course) so I suspect that the electronic thermostat is not engaged when it should so it opens only mechanically at about 108 Celsius.
Everything was just fine before I had that thermostat change few months back. I didn't even know where the coolant was in the car and now this....
Any help or ideas would be much appreciated.

These engines do indeed run at 105/107 for emissions purposes. If Opel/Vauxhall had put the true temp on gauge they would've had everyone calling saying their car is overheating so as long as your gauge is saying 90/92 then all is good.

[niklos4]

Hi trouty

Well, I know that the analogue thermometer in the car indicates 90 for a range of true readings between 90 and 100 Celsius (for phycology reasons I've been told) but mine, after the thermostat change reads 92 constantly (uphill-downhill, cold or hot weather). That was not the case before I change the stat. I had analogue reading 90 and digital 93-98. In its current state the cooling system is overstretched I believe, hence the busted hoses....

[beavor-bob]

If it's the same as the VVT z18 I have, try replacing the temperature sensor - it's hidden at the rear of the thermostat housing a brass coloured thing. Near the heater hoses. It's only about £10 & easy to replace.
These can throw up all sorts of faults if they fail. It is a very important device, as it tells the CPU what it thinks the engine temperature is - in a fault condition, it miss-leads the CPU into thinking the temperature is higher or lower, than it ACTUALLY is.
They can also go open circuit - then the fans will run all the time. It's actually a heat dependant resister or Thermister.
A partly blocked Radiator can give similar symptoms. Good luck.

[niklos4]

If it's the same as the VVT z18 I have, try replacing the temperature sensor - it's hidden at the rear of the thermostat housing a brass coloured thing. Near the heater hoses. It's only about £10 & easy to replace.
These can throw up all sorts of faults if they fail. It is a very important device, as it tells the CPU what it thinks the engine temperature is - in a fault condition, it miss-leads the CPU into thinking the temperature is higher or lower, than it ACTUALLY is.
They can also go open circuit - then the fans will run all the time. It's actually a heat dependant resister or Thermister.
A partly blocked Radiator can give similar symptoms. Good luck.

Hi bob

I will try that tomorrow. Yes, I know where the coolant sensor is. When you disconnect it the radiator fan keeps running (ECU's decision just to stay on the safe side I've read). Thing is though....it sends correct readings -as far as I can tell at least- but since it's a cheap solution, I'll give it a try.