Coolant Temp Light Flickering on my 89 4.0

[Elliot H]

Recently been having a really weird issue, the light for my coolant temp will flicker on and off whenever I turn the steering wheel to the right. I have the base model so there’s no gauge for the temp and it’s just the light, but I have an aftermarket gauge installed and it’s saying that my temp is fine. I had to drive 400 miles with the light turning on every time I turn right, and towards the end of the trip it started flashing more, but my oil level was fine and everything and I had to drive home and nothing seemed really wrong with the truck. Started noticing this after I changed the oil and slightly overfilled, but I drained some of the oil out and it’s fine now. Not sure if overfilling my engine caused this, I was accidentally driving around for like a week with my oil slightly above the fill line without realizing until I fixed that. But now when I was looking at the coolant censors I realized I might have Oil in my coolant reservoir. 
The coolant is really merky and kinda brownish, and when I took the cap off the drops from it look oily. Where should I go from here because I use my truck as my daily and I’ve never had an issue like this. 
 

had a fun time tho driving on the beach and dunes and then 200 miles back home today but I hope nothings wrong with my manche. 

[Minuit]

Which light is coming on? There is a low oil pressure light, and a coolant temperature light, but there is not an oil temperature light. The one on the right is for oil pressure, the one on the left is for coolant temperature.

 

The switch for the oil pressure light is located near the oil filter, and has a single wire connected to it. Make sure this wire is connected well and the connector is in good shape. If your added gauge really is an oil temperature gauge, you'll still want to verify the oil pressure with a mechanical gauge connected in place of the oil pressure sensor to make sure that the light coming on really is a problem, rather than it telling you that your engine is not making enough oil pressure.

[Elliot H]

It’s the one on the left, I thought that symbol was oil temp but I’ll look at the owners manual.

[Eagle]

You don't have an oil temp light, you have an oil pressure light. If it flickers on right turns, it probably means your oil is sloshing away from the pickup and you're losing oil pressure. Check your oil level. If that's good, get an external oil pressure gauge and check your oil pressure.

 

[Minuit]

2 hours ago, Elliot H said:

It’s the one on the left, I thought that symbol was oil temp but I’ll look at the owners manual.

That's coolant temperature. Check on the very back driver side of the cylinder head for another one-wire connection. Make sure it is not loose.

[Elliot H]

1 hour ago, Minuit said:

That's coolant temperature. Check on the very back driver side of the cylinder head for another one-wire connection. Make sure it is not loose.

So I checked the connection and it seemed fine (unless it was the wrong one or something) but I also checked my coolant reservoir and it looks like there’s Oil in the coolant. It’s pretty dark and merky like almost brown instead of the regular coolant color. So idk what to do now because this problem is a lot worse than I thought.