I have a overheating issue with my blazer. It has a 4.3 liter vortex engine, I replaced the thermostat, water pump appears to be working. Anything else I should look at

If your vehicle's radiator is overheating and there are no visible leaks, it is possible that the problem could be caused by a faulty thermostat or water pump. These components are responsible for regulating the flow of coolant and water through the radiator and engine, and if they are not functioning properly, it can cause the engine to overheat.
To determine if the thermostat or water pump is causing the overheating issue, you will need to perform some diagnostic tests and checks. Here are a few steps you can follow:

1. Check the thermostat: The thermostat is located in the engine and controls the flow of coolant through the radiator. If the thermostat is stuck in the closed position, it can prevent the coolant from flowing and cause the engine to overheat. You can test the thermostat by removing it from the engine and checking it for proper operation.
2. Check the water pump: The water pump is responsible for circulating the coolant and water through the radiator and engine. If the pump is not functioning properly, it can cause the engine to overheat. You can test the water pump by removing the drive belt and attempting to turn the pump by hand. If the pump is seized or not turning smoothly, it may need to be replaced.
3. Check the coolant level: Make sure that the coolant level in the radiator is at the proper level. If the coolant level is low, it can cause the engine to overheat.

If you are unable to determine the cause of the overheating issue, it is recommended to have the vehicle inspected by a mechanic who can perform a more thorough diagnostic test and identify the root cause of the problem. They will be able to recommend the appropriate repairs to fix the issue and prevent further overheating.

I see two possible things

There is air in the system and the water isn't circulating properly. Did you burp the system and get all the air out of it. Heater needs to be set to maximum, radiator cap off and keep topping up until the thermostat opens.Turn engine off, top up again and replace the cap.

And, are your cooling fans working? This is something that many overlook.

Also, remove the thermostat, put it in a pan of cold water and turn the heat on. Do you observe it open when the water gets hot?

Unlikely to be a head gasket issue.

if you used some rad sealer the thermostat is probably bad, so it will be overheating, this will blow the head gasket. take the thermostat out and refit. without the it in, go for a drive, the temp should rise up and down. when you come back leave to cool down. and flush the system out with fresh water, and then replace with new thermostat, if no leaks top up with antifreeze and water, leave top off and run engine to get bubbles out of engine squeeze radiator pipes as warming up. and top up water as it goes below line. when all air is out and fan has come on to say its at full temp. leave to go cold. and top up if needed and put cap back on.

Have you tried the thermostat. it might be stuck closed, causing the antifreeze not to circulate through the engine, in turn causing the engine to overheat. Go to YOUTUBE.com and type in "How to change a thermostat on a Chevy Blazer. There you'll get a video on where to look and how to change the thermostat.

There may be numerous reasons for it.

1. Thermostat failing to open

2. Water pump that's malfunctioning

3. Clogged hoses and radiator core

4. Low coolant level

Is it possible the replacement engine has a water pump that turns the opposite direction from the original ?
The thermostat has to be open to allow flow thru the radiator, have you tried running without a thermostat to check flow ?

Question: With the engine cold and the radiator cap removed, do bubbles immediately apprear in the coolant in the radiator when the engine is started? If so, you have a combustion chamber leak into the cooling system inside the engine (blown head gasket, cracked head/cylinder block, etc).
If there are no bubbles immediately, and the bubbles only appear after the engine is HOT, then it may be a leaky head gasket, a sticking thermostat (closed) or restriction in the radiator core or water pump not pumping.


Have a qualified/certified Hyundai Service Technician properly diagnose this issue.

uper radiator hose...replace the o ring gasket of the thermostat element...

The only thing missing from your narration is the water pump. Check to make sure that you are not losing coolant from the water pump. Make sure it is not leaking coolant. If there is evidence of leaking, the water pump is bad. You must take extreme caution when dealing with the cooling system (hot liquid under pressure; not a pleasant thought), but you can remove the radiator cap and start the engine. Check the coolant in the radiator for movement/circulation. If the water pump is functioning properly, there should be some visible sign of water/coolant circulation. The water pump may not be at fault, but with the other upgrades you made to the cooling system, some gunk (for lack of a better word) may have broken loose and clogged the ports in the water hose. You can also remove the hose at the water pump and check for anything clogging up the works. Really sorry for your trouble and I hope this helped. Best wishes.

try your compressor switch or your relay switches, if those dont work it could be your thermostat, your timing is all engine, overheating has to do with your cooling system