My 1999 Chevy Blazer has been giving me some issues with over heating and pissing out all of it's coolant.
The mechanic I brought it to said that I needed to replace the intake manifold and the radiator, so now that's done.
I took it around the block and I ended up over heating again.
I'm losing coolant out of the overflow hose in the coolant reservoir.

Does anyone have any ideas on what could be going on?

 

Take steps to avoid burns here.


Replace radiator cap.




Thermostat. Make sure a new one was correctly installed and is the proper temp rating and is opening at that temp. 190-195 degrees F.



Waterpump. Is the coolant circulating in the radiator with the cap off? Are the hoses routed correctly? Are both heater hoses hot to the touch after warming up?


Radiator. Remove the lower radiator hose and make sure coolant flows from top to bottom while engine is cool to avoid burns. It is possible to get a clogged replacement rad.


Coolant. Most probably you have air in the system if the above checks out. Jack up the passenger side front end and fill the radiator with the 50/50 mix of coolant you are using. Start the engine and keep adding coolant until the bubbles are gone.

 

I am also having the dreaded unknown overheating issue. 2001 Blazer. Is overheating at highway speeds after driving 30min or so. So shouldn't be the fan. I've done two coolant flushes on it with the machine that vacuums it out in the past. I replaced the heater core two summers ago. Does not appear to be leaking coolant anywhere. The level is not dropping and the oil looks fine. As far as I can tell the water pump is working. If I take the radiator cap off and rev it you can see it pull the level down a little. The coolant looks decent. Not all brown and gross. The radiator, from what I can see through the top does not look terribly rusty or anything. The most recent thing I tried was replacing the 195 thermostat with a 180 and replaced the temp sensor. Temp still climbing. I'll probably try the rad cap next since it is the next cheapest thing to try. From what I can see it doesn't look like any of he rad hoses are collapsing. I know some of them are reenforced with metal inside, mine does not appear to be. Any ideas or ways to narrow it down?

...and not sure if it has anything to do with it but sometimes my oil pressure gauge kind of spazzes. Figured it was just the sensor. Haven't noticed corospond with the overheating or anything.

 

Likely the radiator cap is not sealing and holding pressure....go ahead and replace it. Also going to have to get the air out of the cooling system....see above.....

Let us know what happens.

 

Bought a new cap. Had to drive about 40 min this evening. About 5 min from the end of the trip the temp started creeping above 210. I'll try another coolant flush. The machine puts a vacuum on the system so there shouldn't be air in it.

 

So here is the latest progress, or lack there of. I installed a new water pump to at the least rule that out. Bought an electric fan to see if that would make any difference. I may have fried the electric fans thermostat though. I ended up just wiring the fan to be always on for my ride back home. Started creeping above the 210. So the constant fan and changing the fan, also the reduced stress of the mechanical fan being off did not seem to change things. I removed the electric and put the clutch fan back on. Don't know if this helps but I kind kind of keep it from getting too hot by being careful of how hard i push it. I'm about out of ideas as what the problem could be.

 

Curious. Shadow123, maybe you should start a new thread so we don't get your coolant system confused with the OPs. In the meantime, since you mentioned a probable unrelated problem with the oil pressure gauge, you may want to try this. Get an IR temp gizmo and check the engine temp on the thermostat cover and radiator top next to the cap when the engine is at normal operating temp. Then check again when you think it is overheating. Also, even though you are flushing the system, a probability always exists that air is still trapped somewhere. I say a probability only to rule that out. Some other odd ball ideas are one or more brake(s) dragging, the radiator front fins are clogged with bugs or debris, your serpentine belt is slipping and/or your new thermostat could be defective. One would think a simple liquid cooled system problem would be easy to fix. NOT.

 

The fan really only works when you're at idle or very low speed so you can rule that out. If there's no air in the system then my best guess is a partially clogged radiator. After it's warmed up shut down the engine then feel the radiator with your hand. If it's hot on top and only warm on the bottom then you're clogged at the bottom. If it is clogged it's almost impossible to flush it out and you'll need to replace the radiator.

 

Radiator should be under warranty, get another one. Also make sure the lower radiator hose is not collapsing and reducing flow as well.

 

Sounds like a head gasket leak you would see combustion gases bubbling up in the overflow tank this happened on a 98 monte carlo i had turned out the heads warped 11 thousands but that car had aluminum heads. could just be the head gasket is blown ..you can get a block tester loan a tool at autozone but you have to buy block test fluid it will turn a different color when combustion gases are present.