1986 L98 convertible...w/manual trans...

My Low Coolant light went on last week, so I checked my radiator level...It was way down (I couldn't see it)...I also noticed some crap [literally: brown slimy crud] on my rad cap & inlet...So today, I filled the rad and ran the engine for a half hour, then drained the radiator and also removed the knock sensor and oil cooler hose to drain the block...

It didn't look as bad as the cap/inlet, just slightly discolored (brownish vs greenish)...and best news, no scales or flakes...I removed, cleaned, and blew out the reservoir tank...

Now I'm ready to refill it, and reading the FSM, it says to -

"7. Fill radiator to the base of the radiator fill neck and add sufficient coolant to the to the recovery tank to raise level of the 'FULL' mark. Reinstall recovery tank cap.
8. Run engine, with radiator cap removed, until normal operating temperature is reached. (Radiator upper hose becomes hot).
9. With engine idling, add coolant until level reaches bottom of filler neck and install radiator cap..."

Is that right??? In the past, with SBC's, I've always pulled the thermostat out and re-attached that hose and filled the block first...Then re-installed the thermostat & hose and went on to fill the radiator...

Doesn't the thermostat need coolant in the block to open??? Won't the block overheat with no coolant flowing into it until the thermostat opens???

This is not a reverse-flow cooling system, is it???

In an unrelated observance, rad cap off, I also noticed small bubbles in my rad while the engine was running (and fan not running)...and when the fan kicked on, the bubbling stopped, and the level went down...

I am not liking that...

 

Your symptoms describe a leaking head gasket or a cracked head.

 

Just finished engine rebuild on my 87--wish I had seen the coolant re-fill instructions you quoted in your thread. I had a heck of a time getting the air out of the engine block. As indicated, had to leave the rad cap off and add coolant until the level finally stabilized. Not sure removing the thermo stat is an option--once engine is fully assembled, thermostat outlet is nearly impossible to remove. Bubbles in coolant is troublesome but more important is--where did all the coolant go in the first place???? Three places for it to go: external leak; into the oil pan; or out the tail pipe.

 

Seems to me that if you have a 195 deg t-stat and a 200 deg fan switch, then when the engine heats up to around those temps both the fan would turn on and the t-stat would open, causing the block to fill and lower the water level and removing air from the system causing the bubbles to stop. Sounds normal to me.

 

abc

 

Refresh my memory for me - Does the t-stat stay open when it reaches operating temp, or does it cycle open & closed???

The temps my car saw were - Steady operating temp (car in motion, on road) = 177ºF...Fan rarely comes on if at all...Car parked (like today) - 177ºF cycling up to 183º, when fan kicks on...Quickly drops down to 177º again...

What confuses me is the bubbling stopping...Why wouldn't it continue bubbling??? These are very small bubbles; maybe 1/16" dia...Not big bubbles...And not all that many, maybe 10 or 15 at a time...

 

T-stat stays open until a lower temp than the t-stat temp range is reached. It is filled with wax which expands when heated and forces the rod open, when the wax cools it closes. The more it heats the more it opens, the more it cools the more it closes, except the spring actually closes it, but you get the idea.

The bubbling when you first fill it as described in your original post may just be air trapped in the block, so large bubbles perhaps. And then after the tstat opens and it fills the block it is may be air trapped in the radiator core rows which may take more time to evacuate, especially in cross flow radiators (most radiators) Mine is a cross flow in my 95. I am pretty sure yours is too, but I am just guessing. When the tstat opens you should have flow across and since the water is flowing across you may not actually be able to see air bubbles escaping as the water moves by. I am hoping there is circulation. Also it usually takes a little while to evacuate all the air from the little nooks and crannies and rough surfaces in the block and radiator, so some tiny bubbles is not abnormal.

But all this is just occurs usually when initially filling and removing air from the system. Since it was low in the first place there could well be a leak somewhere as mentioned earlier, such as a bad hose leaking steam or worse(replace), a loose petcock (tighten), a weeping water pump (replace), or perhaps even a bad head gasket (ouch). This leaking will allow air back into the system and thus more bubbling. Start with the simple things first.

What temp is your tstat? I recommend only the factory temp range. What temp is your fan switch? Do you see water movement under the cap when the tstat is open and cap off? please do not open hot, Thank you. And of course, check for leaks or steam and seepage, or soft or deformed and worn hoses etc...

This is just what I know from being a backyard mechanic for years, and only owning my 95 Corvette for weeks. So maybe someone else could chime in with some other ideas.

 

I made most of my changes in my ECU & engine 10 or so years ago; I can't get into my old 386 laptop to check the BIN right now (docking station refuses to function) but I hope to get it up & running next day I have off...I *think* I put a 180º t-stat in & set my fan to come on at 200º...but that's just a WAG...

Yes, I can see the coolant flowing from left to right (as seen from drivers seat)...

Tailpipes show no water; leaks, well, right now I can't tell - it's still empty...and it's raining...hard to see leaks...

 

Well, you got flow so it appears the water pump is working, but it might still be weeping. i wouldn't wory about the "Tiny Bubbles" (Lawrence Welk reference aside). Nor the settings if it has been cooling OK for 10 yrs that way. Time to watch it closely and see if it loses more water and track it down.

Good Luck

 

Thanks for all the replies!

I'll fill it up and try it out next day off (I work all daylight hours). Even if it needs head gaskets, I can't do anything until Spring, except drive it occasionally when the streets are clear of snow (I'm in the "Snow Belt").

Hopefully the coolant will flow into the block from the bottom hose enough to start filling when the car starts & the pump is running...It took a 50 mile drive to light up the 'Low Coolant' light, and it didn't take all that much water to bring the level up to the inlet...One quart at least; maybe two...The FSM says it takes 14 qts...

I haven't driven it much in the last couple years; it *may* have been low for a while...

Yes, I'm grasping at straws...

 

OK, my religion doesn't celebrate Xmas (I'm a Druid...We celebrate Arbor day), so I did the refill today...

This is a genuinely terrifying procedure (if your idea of terror is imaging your engine self destructing - mine is)...

I put in 1 gal of 100% Prestone, in half pint doses, waiting for the level to go down, and then 1/2 gal water...Started it up, and watched the temp gauge go up to 256ºF without any movement of the level (as per the FSM instructions above)...Shut it down, let it cool down for about 10 minutes (during which the level went down and I was able to get in another quart of water)...Started it up again, temp went to 286ºF before I shut it down again...Waited, put in another half gallon of Prestone 100%, and started it up for a third time...This time the thermostat opened, and coolant started flowing through the radiator...Got another half gallon of water in it, let it idle for about 20 minutes, no more level dropping, so I put the rest of the Prestone and water in the overflow tank, put the rad cap on and went for a 4 mile spin...

Fan kicked on a couple times while filling it; I'm almost sure I heard *two* fans...My options code reads B4P - Radiator cooling boost fan...Does that mean I have both front & rear radiator fans???

Temp was pretty steady at 173ºF (it was 44º outside here), checked things over when I got back, didn't see any coolant spraying out anywhere, but the bottom ledge of the rad support was wet...Not dripping, just damp...

Don't know what that means...Maybe a small leak in the aluminum radiator??? Maybe just drippings from when I filled it???

I'll check again tomorrow when it's cool...See what the rad level looks like...

...And buy more anti-freeze...

 

Sounds like you got it figured out. As stated some little bubbles during a refill are normal, just little pockets escaping up to the filler. I would keep an eye on the hoses that connect the WP to your heater core, really hard to see the WP connections. Check your heater control valve, passenger side at the firewall. Also could be freeze plugs with a pin hole. No steam out the tailpipe (Head issue)or out the vents fogging the windows (heater core)? Put a piece of cardboard under it to check for drips.

Good luck!