1998 S70 Engine Temp Fluctuation after Tstat and ECT replace

[mecheng]

I don't, any recommendations for a decent gauge.

I use an App called Dash Command on my iPhone with a ELM327 WiFi adaptor

If you have Android you can use a ELM327 adaptor that uses Bluetooth, they are a bit cheaper.
A lot of the Android fanboys use an app called Torque.

I bought the adaptor from ebay and the DashCommand app was $10.

If the temp is sitting at 3 o'clock and you have Volvo parts you are probably okay. I would check cylinder compression to confirm the headgasket is okay.

[westroxvolvo98]

Hi Guys,
I have been nervous about a blown head gasket since it was mentioned here the other day. I did check my coolant this morning and it seems to be dropping slightly (I filled it up on Monday night) and the coolant color also looks a bit brownish to me (possible oil contamination).

I have also been having issues with rough starts for the past couple of months now and the engine codes have been multiple cylinder misfires. The strange thing is that about 30 seconds to a minute after it starts, the engine smooths out and is running fine. I have read on multiple forum posts this rough starts can be from bad wires, plugs, distributor cap, coil. All of these parts have been replaced on the car within the last 20,000 miles or so and are OEM parts.

Does anyone think the coolant issues and misfires could be head gasket related? The car seems to be running to well for a blown head gasket.

[mecheng]

Do a compression test and post the numbers, it will tell you everything you need to know about your engines health. Make sure the engine is warm.

[erikv11]

I agree do a compression test but keep in mind that unfortunately it is not nearly sufficient for diagnosing OR ruling out a bad head gasket. Basically, the head gasket separates three chambers (cooling, combustion and lubrucation i.e. oil) and a head gasket breach can be between any two of them, and leak in any one or both directions.

So, for example, a coolant passage that leaks into the cylinders under pressure will not always show up on a compression test. For that problem (and this may be relevant here), you also need to do a cooling system pressure test. For an engine with oil leaking into the coolant the compression test may be perfect; for that one you just have to go by oil in the coolant (and not get fooled by oil leaking in from a bad radiator).

The other test often needed (probably not needed here) is to look for combustion gases in the coolant. For whatever reason, especially on these cars it is common for the cylinders to hold compression just fine but for the head gasket to be blown in that way.