Ok, I'm in the middle of trying to flush my radiator prior to pulling it off the car ('83 GSL) for refurb. I pulled a hose off the lower radiator (the smaller hose that goes to the heater core) and got a bunch of coolant out. Then I pulled the block drain plug and got a bunch more coolant out of there. I put the plug back in, and the hose back on. Then I started filling the radiator with distilled water (plus a bottle of flush solution). It only took about a gallon, so I figured the new water probably wasn't getting to the block because everything was cool and the thermostat was closed. So, I pulled the top radiator hose and the thermostat housing. I poured more distilled water down the neck into the block - was another gallon or so of water. I then put the thermostat, housing and top hose back on. I started the car and was letting it warm up...

After 20 minutes or so, the temp gauge was climbing, but I was not getting heat (from the heater core) - and the radiator cap (and hoses) didn't seem to be warming up at all. The oil filter was warming up. I was thinking the thermostat just wasn't opening up yet, but eventually the temp gauge hit about the half-way point and I decided something must be wrong. Turned off the car. Radiator still seems stone cold - engine block is quite warm.

What the heck did I do wrong? Thermostat and radiator hoses were all replaced last year - looked in fine condition. Water pump was spinning - I can only assume it was at least trying to pump as it the car seemed to be working fine before I began this.

Any thoughts greatly appreciated. I've got about 3 hours before the flush needs to get back out of the system (according to the label).
Thanks!

 

Well, is the tstat in correctly? Did you burp the system? There may be air thats keep the tstat from opening cause it doesn't have hot water touching it yet. To burp it just squeeze the lower hose and have the cap open on the radiator. Also did you make sure the tstat jiggle pin was at 12 oclock so air will get passed when its closed? I think its some thing todo with your tstat for sure.

 

Hey - thanks so much for the quick response and ideas!

I pulled the thermostat out entirely. It was in correctly (long side down), but mine (which is an aftermarket, not Mazda apparently) does not have a jiggle pin. When I pulled it, the cavity it sits in was full of coolant, so it seems like it should have been able to do its job. I had not burped the system as you describe though, so it's quite possible that was the issue.

I had pulled the thermostat before getting your post, and just reinstalled the top pipe without the t-stat installed. I started the car with the rad cap off and I could clearly see a flow in the coolant across the neck opening. With the thermostat out the car never really warmed up (temp gauge stayed at the bottom of the dial) but the coolant in the radiator did get noticeably warm and I was able to get some heat out of the heater core. With that I'm confident the coolant was flowing, so I'll just drain and flush again with fresh water to get the flush chemicals out of the system before a final drain to pull the radiator. I will deal with the thermostat when the radiator goes back in...

once again - thanks for pointers!

 

if the t-stat doesn't have the jiggle pin hole, then punch one into it, so the air can go through it and the warm coolant can touch the t-stat and it can open

everything doesn't have to be ordered out of a catalog

 

I'll give that a shot - thanks!

 

But this is why a lot of folks like an OEM tstat, so it works out of the box.

 

Additionally, that "long end" as you call it, has a plug that mates with the step inside the housing which blocks coolant flow from going into the bypass. When you remove the thermostat and run the engine, the coolant follows the path of least resistance and will bypass your radiator entirely, allowing the engine block to overheat.

Don't do that. Always run the engine with a thermostat installed, OR do your homework and research how race cars (*track cars...) weld a plug in the bypass port to allow them to run without a thermostat, recognizing that track race cars are running at WOT 99% of the time, and need maximum cooling flow. If his is a street car, you definitely don't want that.

I've removed my heater hose connections and blocked the radiator and engine block ports, but I live in the middle of the Sonoran Desert. Still, I always run a thermostat and an OEM one, wih the jiggle pin, at that. Once your flush is complete, get a thermostat back in there,

 

Sorta off the subject. I've read a number of automotive articles that say never use distilled water in your cooling system. Here's one with a good explanation.

https://www.hyperlube.com/blog/blog/...ooling-system/

Any thoughts from my more experienced fellow members ?

 

Yep - the removal of the thermostat was only to get through the flushing step.

 

I wonder what the pre-mixed stuff is mixed with? I admit that I've always used distilled water in my vehicles.

I've only had the replace one radiator (RX7), but that was due to the fins disintegrating, no leaks.

Interesting article, but the issues they raise are above my pay grade 😛

 

This article gives more context to why you don't get salt in your faucet water and explains why salt is consumed in the process. TL;DR the salt is used to process/refresh the resin beads in a nightly refresh with a completely separate water circuit. The refreshed beads with Sodium ions (not NaCl table salt) are what actually get exposed to your "production" water flow and these beads remove the minerals.

https://www.scientificamerican.com/a...-softeners-wo/

 

Following my coolant system overhaul (including OEM thermostat!!!), I found it helpful to raise front end of car, rad cap open, and squeeze and release the upper and lower rad hose a bunch of times. Add more coolant, and repeat.

This seemed to get all the air out before even starting the engine and allowing a warm up cycle.

And make sure your rad cap is good also. A bad rad cap can cause a poor seal, and on cooldown, you wont have a good vacuum to pull coolant back into the rad from the expansion tank. Will make it seem like you are losing or leaking coolant, but really just hiding it in the tank.

And I always say, use OEM parts where you can. Get a thermostat from any local dealer, just a phone call away.