My first post so don't lambaste me too bad if this has all been gone over before (I know there are a lot of threads on water temp issues with the LT1 but thought I'd throw my situation out there so I can take a remedy back to the mechanic or at least provide him with some thoughts to correct the issue). The story is I had the water pump and opti spark replaced just the other day. Prior to this my water temp (digital readout) on the highway was 185-190 and around town (summer days) would reach 210-215 and sitting at a light it could reach 220. Now since the water pump replacement my highway temp is 205-210 and around town (temps are only in the low 60s this date) high 190s-200. Sitting at a light the temp doesn't go anywhere near 220 like before, might get to 205. When I pop the 'hood' I find a cold overflow reservoir and the coolant level at cold (it is obvious no hot coolant from the engine has made it to the overflow reservoir). I also find some leaking coolant around the cap on the pressure tank. It also appears one of the hoses connected to the tank may be leaking a bit. Those items I will fix once the engine cools down (assuming the cap is not sealing).

The cooling system was not flushed upon water pump replacement. I am concerned the system was not bled properly. I did add some coolant to the pressure tank the day after getting it back because it was about an inch below the top. No coolant expanding and going to the overflow reservoir concerns me also. This does not seem normal. Plus, I am assuming they used the old T-stat but I will check with them to insure they either used the old one or put in a proper LT1 T-stat. The engine gets to temp much quicker than before the pump replacement. I am just looking for what may be the obvious route to take that I can relay to the mechanic (at a well respected performance shop) so I can be sure I have a properly cooled engine. Maybe a complete flush and refill is the answer. It does have 102,000 and I have no idea what previous maintenance has been done (I've only owned the car one summer).

Thanks for any advice and input. Sorry for the book length post.

 

Most don't recommend a chemical flush. With aluminum heads i would not recommend flushing with the motor running. Plenty of people will argue that but i opt to remove the knock sensors on the bottom of the block and remove the lower radiator hose yearly to drain and force water down the thermostat hole to flush. The reason for not using a chemical flush is to prevent damage to the radiator and heater core. All your leaky hoses need to be repaired and high quality / correct thermostat installed. I use a 180* and i live in Texas. Make sure to bleed after fluid installation with the engine running.
The radiator inlet is like a street vacuum, bringing up all the trash and leaves which blocks the radiator. Check for obstructions regularly.

 

Nice job of describing your cooling condition. It really helps when all
the conditions are presented.

LT1 is self-bleeding. Coolant on the surface of the surge tank could mean: hose leak, cap gasket damaged, or the throat of the surge tank may be split. The original cap requires considerable torque to remove it, so some have had tools (slip-joint pliers) applied which can split the thin brass throat material (pic displayed below).

The overflow bottle should contain warm coolant with a hot engine.
The expanded coolant may be flowing out of the surge tank, hose, or surge tank neck rather than flowing to the overflow bottle.

Possible fracture of fill neck:

 

I believe you stand corrected, Sir. The 92 has a coolant bleed at the large radiator hose connection near the thermostat.

 

The LT1 engine is self-bleeding: http://www.calgaryfieros.com/OSGdocs/mod.LT1.html

And, yes, I'm quite aware of the bleed screws, thank you.

 

A quote from the Factory Service Manual would have more validity.

 

Thanks for the info. I will check the neck thoroughly. A new cap is also warranted. One question on the cap - it is marked as a 15 lb. cap but when I look it up at parts sites they all say 16 lb. Is that 1 lb. going to matter if I can't find a 15 lb?

Makes sense coolant would not get to the reservoir if escaping beforehand. Afterward if neither of those items resolves the situation I may try to burp the system a couple of times.

 

A 16# pressure cap is just fine. You will find the new caps are
"easy on & easy off", and all new caps are for both 'open' and 'closed' systems. Most caps are made by STANT and packaged under various brands, including ACDELCO. Note the copper rivet in the center of the cap..... a STANT cap will have a large "S" stamped in the center.

Burp the system all you want.... just wasting time.... run the engine, and it will burp itself.

 

Thanks for the info. I did buy a Stant 16 lb. Car temps have not changed. Coolant reservoir level is still only at 'cold' level after driving and even getting temp up to 228. I blew out the hose to make sure it was clear. However, the reason may be related to the fact I still have coolant seeping out from somewhere either around the filler neck on the expansion tank or a hose connection on the expansion tank. It is maddening trying to determine where this coolant is seeping from. The lower inlet was leaking and I have tightened it far beyond what I am comfortable with using new stainless steel helical screw clamps so I believe that can in no way be leaking and the upper is also tight but still have coolant around the lip of the expansion tank when I park it. So I suppose a new expansion tank is next step.

I have been reading about the self-bleeding design of the LT1 so I have to agree burping the system is unnecessary. Quite an ingenious design for the early 90s.

 

Seabright knows what he is talking about. I thought my cap had a leak and it turned out the neck on surge tank had a hair line crack. I didnt notice it until he posted the above picture. New surge tank and a few new caps that i didnt need and ive been good for months. Dave

 

Found the outlet where it seats in the expansion tank neck is loose and leaking. That should explain why no coolant making it to the overflow tank (the leak is small in terms of volume but must be having some affect). Ordering a new expansion tank unless someone knows of a fix?

 

That should be a solid fix...... FYI: the new surge tank comes with
a "low coolant" sensor located in the bottom of the tank.

 

The crack in the surge tank neck allows air to enter the system preventing pressure from raising the boiling point. Also, a breached
system will not allow a siphon to form, negating a flow of expanded coolant from the overflow bottle back to the surge tank.

With the new surge tank installed, just take a drive to reach operating temp. When the engine cools, remove the cap and add coolant, if necessary.

http://www.tuneruniversity.com/blog/...-radiator-cap/

 

Thanks for all the great info. I hope with the new expansion tank I can take a break from wrenching on this car and drive it!

One last question - I seem to have a hard time tightening the lower hose to the tank. Even if the clamp seems tight (screw type stainless) I can turn the hose on the nipple. I have to really reef on it to get what I consider tight (not able to turn the hose). I feel like I am damaging the hose by the slots in the clamp really embedding themselves in the rubber. I shouldn't have to tighten down on this so hard in order to have a leak free connection. The nipple has the flare which should do the majority of the sealing and the clamp being behind that shouldn't have to be tightened as hard as I am. Any thoughts?

 

If you are describing the lower rad hose to the block, it sounds like
the hose wall has turned to 'mush'...... buy a new hose.

Make sure the worm clamp isn't missing a 'link', and just spinning.