My 97 Blazer is running hot and I have no idea why. I had a salvaged engine put in it in 09 and the waterpump was leaking. The shop put stop leak in it instead of fixing the problem. Since then I have put a new waterpump on. Then 2 freeze plugs rusted out and it ran hot and I had to replace the heads. Now it keeps having this build up of this muddy looking stuff in the radiator. I flushed it out yesterday and put water back in it and now it is running hot. The thermostat has been taken out. Also I have been able to turn on the defroster to help keep it cool before and now the defrost doesnt get hot but the engine is still running hot. Please help if you can this is my only car at the moment and I really need it!

 

Did you put any antifreeze in it or did you just use water?

 

Have you checked for or had the cooling system evacuated from air?

(Dexcool & rad sealant is a bad idea... actually any type of rad sealant is.
Your cooling system & maybe the heater core may be plugged with that crap but try to evacuate air 1st.)

If not there is an old school method that works well.
Fill the rad with the coolant & let it idle to normal operating temp so the thermostat is open with the cap off.
Check the level.
Lift or drive on a ramp so the PS (rad cap side) is elevated.
Then check the coolant level & top up as needed.
Rev it to 1000 or so for a minute or so & let it idle. Do that a few times to "burp" the system of air. Keep an eye on the rad level & make sure your reservoir tank has the right amount of coolant in it. <--- that only matters after you have the cap back on.
You can run the heater in the cab for another way to check for air in the cooling system. If it's just ambient air temp = you have an air bubble. If it's warm/hot air = it should be free from air.

 

Hate to say it but sounds like the shop used the sealant to have a repeat customer! If a shop ever wants to put a band aid on a problem, especially a serious one like coolant leaking then RUN!! If they cant fix a vehicle properly then they shouldnt be in business. The sealant is notorious for clogging a heater core and ur heat goes and then comes the water in ur pass side floor not to mention engine overheating a common sign too...sometimes the order is reversed or can happen bout the same time. The only time I had a heater core go bad the first sign was engine running hotter than norm and same with turning the heat on to keep it from getn too hot until i no longer had heat. Changin those is NOT fun either...good luck and if it were me I would be speaking not so kindly to the shop owner and get my money bak!

 

How rude Mel can be lol. But she's spot on IMO. No rad gunk, it's only more issues.

 

Thanks everyone for the responses! Yes I put antifreeze in it and the shop is a Universal Technical Institute graduate and his shop is in Houston, Tx and im all the way in Alabama or I would be there shoving my foot up his butt.

 

You can try to back flush the heater core. It will probably take several flushes but if that doesn't work, then a new core is in your future.

 

Im not rude...just blunt lol If what 50lb_cat doesnt work and u cant/dont want to get it changed or deal with it later u can always bypass it

 

You should get the proper thermostat in there, without a thermostat you have the possibility of water going too fast through the radiator to cool it down or possibly not allowing proper restriction for coolant to flow as designed.

 

The mud in the cooling system is caused by mixing Dexcool, (orange) and ethylene glycol, (green) coolants. You will need to use a chemical flush agent and flush each component separately, (radiator, block & heater core) in both directions, until it comes out clear. Fill 50/50 with Dexcool & distilled water, (not tap water). There are 2 other options: 1) take it to a reputable shop and have them do it. 2) Don't do anything and let the engine destroy itself