2021 GMC Sierra 1500 · symptom sheet
Engine overheats or leaks coolant
- 53owner reports
- 98,500median miles
- $499median quote
- 0involved a crash
Newest report Sep 14, 2026 · checked Oct 2, 2026
350 of the 573 complaints on this car are about the engine. 53 of those describe overheating.
Tick what matches of 53 reports
Overheating on other Sierra 1500 years
No other Sierra 1500 model year has enough reports of overheating for a sheet of its own. See every Sierra 1500 year.
What this problem usually is
Most owners in this group notice the coolant before they notice the heat: a reservoir that keeps dropping, a sweet smell, or a bright puddle under the front of the car. Across the vehicles on this site, about four in five of these complaints mention coolant, a leak or a puddle, and roughly two in five mention the temperature gauge or overheating.
What got replaced
Owners who name the part that was replaced mention the radiator (4 reports) and the coolant hose or reservoir (3 reports).
Recalls and investigations
One recall on the engine covers the 2021 model year. A recall on the same system isn't always the same failure, so read the defect text.
The connecting rod and/or crankshaft engine components may have manufacturing defects that can lead to engine damage and engine failure.
All 7 recalls on the 2021 GMC Sierra 1500, with the owner complaints on each recalled system
NHTSA investigations into the engine on the Sierra 1500
Loss of motive power due to engine failure post recall remedy. Open.
Loss of motive power due to engine failure post recall remedy. Closed aug 20, 2026.
Loss of motive power due to engine failure. Open.
Loss of motive power due to engine failure. Closed oct 23, 2025, led to recall 25V-274.
What owners paid
13 of the 53 reports quote a price. Each dot is one quote. The middle half runs $395 to $2,400.
When it happens
The middle half of failures fell between 50,000 and 122,691 miles, from the 14 reports that gave a mileage.
Is this a known problem?
The manufacturer has sent NHTSA 16 service bulletins or notices for the 2021 GMC Sierra 1500 that deal with this problem. Newest first.
Federal rules make a manufacturer send NHTSA a copy of any notice about a defect that goes to more than one dealer or owner. Most of these are service bulletins, the repair instructions manufacturers send to dealers. NHTSA generally leaves safety recall bulletins out of this file, and recalls are listed separately.
Certain vehicles listed above, may have a condition that could cause the engine coolant control valve to fail an onboard vehicle diagnostic test.
This service bulletin advises the technician of possible coolant entering the areas of the engine, either through failed parts or defects in the castings, that may be the cause of the concerns related to the MIL or the engine running rough.
This bulletin advises the technician of a possible kinked coolant hose that might be causing the customers concern of a Malfunction Indicator Lamp (MIL) Illuminated - DTC P026A Set.
This Preliminary information communicates to dealers? information related to a Malfunction Indicator Lamp (MIL) Illuminated due to a U0672 setting. Advises the technician to perform Electric Engine Coolant Pump connection inspections.
12 more on the 2021 GMC Sierra 1500 page.
What owners wrote
“I have a 2021 GMC Sierra 1500 AT4 3.0L diesel pickup truck with 98,500 miles. The coolant control valve failed on my vehicle and for some reason it is not covered under GM's special bulletin that covers this part 15yr/150,000. Ridiculous.”
Filed Apr 8, 2026 · 98,500 miles
“I had an engine warning warning light on my dash around May 5th. A notice of reduced speed also lit up my dash while I was on the freeway. I scheduled a service for May 15th and was told the engine coolant flow control valve needed to be replaced. I was also told there was a backlog of other vehicles waiting for the same part. It has been over a month and I am still unable to drive my truck which I use for work.”
Filed Jun 17, 2025
“The truck ever since of bought it has been nothing but issues. Starting with the fuel pump issues then electrical issues and most recently the coolant flow control valve. This is my work truck and now Iâm out of a truck with no loaner and the dealership has no eta.”
Filed May 29, 2025
“code P1098. Engine light comes on, power is reduced, coolant fan runs on high. Temp gauge fluctuates. This last for 20 minutes or so. The engine then returns to normal. After a few days the engine trouble light goes off. This happens every several weeks. Parts are backlogged and I understand this is a common problem with this engine. I have 64000 on it.”
Filed May 19, 2025
Should you keep driving it?
This page can't tell you that. 0 of 53 reports involved a crash. Owners who file are the ones who had a bad experience, and nobody checks their reports. If the problem affects steering, braking, power or a fire risk, treat it as a safety fault and have it inspected before a long or high-speed drive.
File your own report with NHTSA. Complaint counts are how a problem gets an investigation. How reports land on this sheet.
Guide Which lights mean pull over now? Warning lights by color and urgency
Other problems on this car
- Engine failure, knocking or rod bearing 126 reports
- Check engine light or misfire 104 reports
- Engine stalls or loses power while driving 88 reports
- Transmission shudders, slips or shifts hard 43 reports
- Infotainment, screen or backup camera fails 26 reports
- Engine rattles or ticks 26 reports