metheglin

I flushed my radiator and added new fluid. Now it overheats.

1 week ago -- added dishwashing liquid to radiator
3 days ago -- drained and flushed and back-flushed the radiator, leaving it full of 100% water (no antifreeze). Installed a new thermostat and gasket. (cooling system was working fine at this point). Patched hole in inlet-side tank with steel-putty (didn't have solder at the time)
Today -- chemical flushed system. 30 minutes drive with water + chemical, then flushed with plain water. I took the thermostat out when I rinsed it, and left the upper radiator hose disconnected at the radiator end of that hose, running the engine to pump fresh water through every part for a full rinse (garden hose filling radiator). Then I put the thermostat back.

Now it overheats. Coolant is not circulating. Radiator feels cool. There are no leaks, and there is plenty of pressure -- when I remove the cap there is a hissing, but no steam because I'm not letting it get over 230.

I tested the thermostat in boiling water, and it opened fine. Besides, it's only a week old. I'm pretty sure I've got it installed the right way, with the spring part down in the engine, and the little tip pointing up. That is how my auto mechanics book says to install it.

When flushing, I noticed that the water pump is intermittant -- sometimes the engine would draw in water and shoot it out the top hose. Other times, water would run out the top of the radiator instead. Is that normal?

The suspects are:
1) Lower radiator hose is collapsing under vacuum and blocking flow (I'll watch for that next time I test it)
2) Thermostat is sticking, but only sometimes.
3) Giant air bubble? messing up the flow? Is that possible?
4) Water pump troubles.

Ideas?

noonie

Read thru this thread first.
http://forums.corvetteforum.com/show....php?t=1582996
Sounds like your flushing methods may be in question. There is a link to a GM tech paper there for flushing. Very good directions.

Try leaving out the tstat for an intial flush. You can see if the wpump pumps coolant thru the radiator tubes below the cap housing. If you can't see flow, you may have to have the rad rodded.

Also remove the 1/4 pipe plugs on each side of the block to flush engine.

mikem350

I vote for air pocket. Happens when the thermostat is closed and the hot water can't get to it (after flushing).

Some thermos have a small bleeder hole (like a bypass) to help this problem. I drill two small holes (carefully) on the flat part.

If you wait long enough the thermo will eventually open. You will notice then that the water level drops and you have to add more. Good Luck!!

metheglin

I know my flushing method was a bit goofy, but I think it was adequate. Soap, pure water, then mild flushing agent, then pure water. I missed draining the block, but I think that the water pump was able to throw enough water through the engine to get most of the dingy crap out. The only thing I'm not too happy about was the 3 day lag with just water in there, with no rust inhibitors.

The GM procedure linked in the other thread requires a lot of stuff I don't have (flush kit T, temp scan tool, etc), and was written for a different much newer car. But thanks for the link, it's enlightening nonetheless.

So I'm gonna assume I should leave the cap off, so I can see in right?

The radiator worked fine before this flush. Do you think something broke free and then jammed it up?

Yeah I missed that part, but it's too late now, unless I start over and flush it a third time.

I noticed just now removing the cap that the radiator tank was empty for as far as I could see... no drips on the ground.... maybe i just didn't add enough coolant.
Where is the coolant going? Is there just a big bubble getting filled? God I hope it's something simple like that. I added coolant and ran it until hot. But squeezing the top hose, there wasn't the feel of water rushing through it. That worries me.

I'll check the level again tomorrow morning.

metheglin

I missed your post somehow (while writing mine?)... this sounds like exactly what happened. [Imagine a smiley wiping it's forhead and sighing with relief]

noonie

Not trying to scare you, but unfortunatly this has been known to happen.

The reason why the GM paper insists on the flush time is so that the chemical reaction can break down the scale etc into fine enough particles to be put into suspension so that they will not plug the radiator, rather than just break the big pieces loose and possibly plug the rad. Hopefully this is not your case.

The GM paper is for later models, but it still applies. Just don't use the parts/tools that don't apply.

If you don't drain the block with the engine pipe plugs, you are roughly leaving 2/3 of the coolant in the engine. It just creates a better job. Keep in mind, the plugs are put there for a reason.

Hopefully, as you suspected, you just had some large air pockets and not enough coolant. Run the engine to view the flow from the tubes until hot and keep filling as the level goes down. With the bleed holes in the thermostat (in other thread) it should fill rather quickly.

Having a clean cooling system is just good preventative maintenance.

Glassbowtie77

Sounds to me like an air pocket. Make sure you have the radiator cap as the highest point in your cooling system. You can do this by jacking up the right front side of the car. Run the car up to operating temp with the cap off and the the heater on Hi with the temp control all the way over at hot. Hopefully once the t-stat opens it will burp the air out of the system. Once you have all the air out, lower the car, top it off, replace the cap (15 or 16lb.) and you should be good to go. Good luck, hope it works out.

chrisd0729

Just went through the sme thing- here's my thread: http://forums.corvetteforum.com/show....php?t=1583157

Drill the hole in your tstat before you waste anymore time and see if that helps.

JPhil

3/32" or 1/8" hole in the flat disc.

In case it helps, here's a post (by me) I copied from a previous thread about flushing out cooling systems:


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When I replaced the 3 month old Dex with Zerex GO5, I stuck a long piece of 3/8 oil line through the rad filler neck down to the bottom and siphoned it while the block was draining from the drain plugs. Replaced the plugs, filled it with the hose, started the engine. After it came up to temp and the t-stat opened, I started siphoning with the hose again. After a couple gallons were in the bucket, I topped it off from the hose again. Did that over and over, took probably 20 gallons untill the water was absolutely clear. Then I siphoned the rad dry, drained the block and called it good. Add distilled water and GO5.

A hint for you guys who were never gas-stealing hooligans:
To safely siphon a tank, stick your hose in but then take a rag and wrap tightly around the hose and stuff it into the filler neck to make a tight as possible seal. Then BLOW into the hose to build pressure in the tank to get the siphon started. Once it's going you can pull the rag off.

John

metheglin

I forgot to post my results.

I drilled two 1/16" holes, in opposite sides of the flat part. I didn't want the holes to be too big, because I want to make sure there is very little flow during the warm-up period.

Worked like a charm. Topped up, and now the temp stays pegged. I don't know how to read the temp gauge exactly, because it's not linear, but it stays right in the middle of the second zone:

JPhil