1998 S70 T5 -- P0116 thermostat and sensor?

[mar601]

Getting this code. From what I gather, may be the thermostat and coolant temperature sensor?

Autozone down the street has both parts -- is an aftermarket thermostat ok?

Should I get the 194 degree part? (90 celsius I think). THANK YOU.

[mecheng]

I replace both as it is not clear which is at fault, and the thermostat from the dealer is only $20, and while you have access it is a good idea as the thermostat will eventually fail.

I replaced the sensor only once, because the thermostat looked ok and the code came back. It looked okay, but I don't think it was sealing perfectly.

Now I know how to test the sensor, so next time I may test before replacing but always repalce the thermostat: cheap insurance.

I recommend to use the dealer parts, both are German made. The ECT is critical the engine perfomrance and fuel economy; and the aftermarket sensor may not be as precise or last as long.

[JRev]

Always use volvo genuine for these parts as Its virtually guaranteed that aftermarket parts will fail for sensors, in fact all sensors stick to volvo genuine as you may get lucky but from my experience of installing sensors and thermostats once you start buying aftermarket you buy twice.

[mar601]

How did you test the sensor? My business is electronics so I imagine it's a simple resistance reading?
Yes, always try to get OEM parts but Volvo isn't close today -- although this doesn't sound too critical and maybe can wait a day or 2? -- the inside engine temp gauge is fine, a little on the low side actually.

[mar601]

and if I remember, there's a gasket for the thermostat housing ? -- do you use hi temp silicone on it?

thanks very much -- I mean that -- this forum is great.

[JRev]

How did you test the sensor? My business is electronics so I imagine it's a simple resistance reading?
Yes, always try to get OEM parts but Volvo isn't close today -- although this doesn't sound too critical and maybe can wait a day or 2? -- the inside engine temp gauge is fine, a little on the low side actually.

As far as I know, if the ECT fails then there are default settings on the ECU that are used so you would be better off waiting until you can get a volvo genuine part, a few days isn't going to make any difference and the inside gauge should always sit at 3'oclock , once warned up it should never move, if its moving, especially at highway speeds then the thermostat needs replacing but as they are in the same area then if you go ahead and use volvo genuine for both then you won't need to do the job ever again.

I replaced both myself and was running with a faulty ECT for awhile without knowing but it got to a stage where it caused problems starting the car as initially it was wrongly diagnosed yet just hold on until you can get OEM.

[erikv11]

The standard resistances for the ECT at different temps can be found by searching this forum, it is a straightforward test that has been posted about before.

When the ECT fails, the ECU uses the bad info from the ECT and does all kinds of wonkey air:fuel things. Unfortunately, it does not go into default.

Gates is a good aftermarket brand, they are known to sell the Wahler (OEM) stat in the Gates box. The aftermarket gaskets also can be terrible, instead of rubber they are a waxy plastic that falls apart quickly. The Gates gasket is nice.

I've never heard of a bad t-stat that throws a code, they usually just affect the operating temp of the engine.

[erikv11]

Also this is a good time to check the wiring on the connector to the ECT. It is a known weak spot and sometimes a "bad ECT" can be traced to a frayed wire or bad pin at the connector.

[mar601]

Cool -- so narrows it down to the ECT -- I'll check it tomorrow and exercise the connector + spray it with denatured alcohol. Got the code this morning, reset it and nothing this afternoon.

Thanks -- so damn busy right now, nice to know it's not pressing.