The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2017 Cherokee Trailhawk Overheating on Highway - P0128 Code

0

Brittany E. · rep 0 · May 22, 3:23 AM · 1 replies · solved · Question

Vehicle: 2017 Jeep Cherokee Trailhawk

Hi everyone,

I'm having a persistent overheating problem with my 2017 Jeep Cherokee Trailhawk, 3.2L V6, with about 70,000 miles. It seems to happen mostly on the highway or when I'm driving at sustained speeds. The temperature gauge will slowly climb towards the red, and I've had to pull over a few times to let it cool down.

I've also noticed that the engine takes a long time to warm up to operating temperature, and sometimes the heat inside the cabin isn't as strong as it should be. I scanned it and got a P0128 code, which I know is related to the thermostat. Could a bad thermostat really cause overheating on the highway like this, or is there something else I should be looking at? Any advice is appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:23 AM

0

ClearTheCode admin answer:

The P0128 code (Coolant Thermostat (Coolant Temperature Below Regulating Temperature)) strongly suggests that your thermostat is stuck open or opening too early. While this typically causes an engine to run cooler than optimal, it can indirectly lead to overheating in certain scenarios, especially if it's not fully closing or if there are other underlying issues. Here's a breakdown:

  1. Stuck-Open Thermostat (Primary Suspect):

    • Cause: A thermostat stuck open allows coolant to continuously flow through the radiator, preventing the engine from reaching its optimal operating temperature quickly. This explains the slow warm-up and potentially weak cabin heat.
    • Overheating Link: While counter-intuitive, a faulty thermostat can sometimes cause erratic temperature regulation. If it's not functioning correctly, it might not be allowing proper flow when needed, or it could be a symptom of another issue stressing the cooling system.

  2. Other Potential Overheating Causes (to consider if thermostat replacement doesn't fix it):

    • Low Coolant Level: Check your coolant reservoir and radiator (when cold) to ensure proper levels. A leak in the system can lead to low coolant.
    • Clogged Radiator: Debris or internal corrosion can restrict coolant flow through the radiator, reducing its ability to dissipate heat.
    • Faulty Radiator Fan: On the highway, airflow usually cools the radiator, but if the fan isn't working correctly, it could struggle at lower speeds or if the engine is under heavy load.
    • Water Pump Failure: A failing water pump won't circulate coolant effectively, leading to overheating. Look for leaks around the pump or unusual noises.
    • Head Gasket Issues: A blown head gasket can allow combustion gases into the cooling system, causing pressure buildup and overheating. This is usually accompanied by other symptoms like white smoke from the exhaust, coolant loss without visible leaks, or oil in the coolant.

When to See a Shop:

Given the P0128 code and the symptoms, start by replacing the thermostat. This is a relatively inexpensive repair and often resolves these issues. If the problem persists after replacing the thermostat, or if you notice any other symptoms like significant coolant leaks, unusual engine noises, or persistent white smoke, take your Cherokee to a trusted mechanic immediately. Overheating can cause severe and costly engine damage, so it's crucial to address it promptly.

Menu

Help & account