Coolant issue

[secondchance]

I have a strange situation. As the coolant get hot (normal operating temp) it overflows into the overflow tank at front right of the car - so far so good. As she cools, expansion tank does not such the coolant back from the overflow. After the car has cooled, when I open the radiator cap (17 lbs rated factory cap) I hear pressure being relieved and bubbles going into the overflow tank. Not only that but also I find the radiator expansion tank about a gallon short from being full. It almost looks like expansion goes to overflow tank but the cooling system cannot replenish as the system cools down.
Any thoughts?

Is it normal for the expansion tank to be about a gallon short when the cooling system is cool ?

[Marc Haibeck]

That's not normal. The black surge tank should normally be full to within an inch of the top.

There could be a defective radiator cap. Or there could be an air leak on the line that runs from the surge tank to the overflow reservoir. When the engine cools it draws vacuum on that line to pull the coolant back into the engine.

Hopefully that takes care of it for you. A leaky head gasket will also overfill the white reservoir tank.

Best of luck.

Marc

[secondchance]

I sent you an e-mail also. Another symptom is steaming driver side exhaust after about 2-3 minutes of cold start. Another 3-4 minutes steam goes away. Is this indicative of head gasket issue? Would use of GM radiator supplement tablet help? I did replace IH gasket and plenum gaskets. Also no sign of contamination between the coolant and oil.

[Marc Haibeck]

The combination of coolant overfilling the reservoir and steam in the exhaust is bad news. Does the exhaust smell like coolant? The most common cause is an injector housing gasket but you know that yours are okay.

Look for bubbles entering the coolant reservoir. If there is a steady stream, that is strong evidence of a leaky head gasket. I like to sample the air in the overflow reservoir with an exhaust gas analyzer. Basically, there should not be any exhaust in the coolant. Detecting over 20 ppm HC is also strong evidence of a head gasket leak.

Stop leak may help for a while. I don't recommend it.

Sorry to be bringing only bad news.

[secondchance]

[QUOTE=Marc Haibeck;175366] I like to sample the air in the overflow reservoir with an exhaust gas analyzer. Basically, there should not be any exhaust in the coolant. Detecting over 20 ppm HC is also strong evidence of a head gasket leak.
QUOTE]

Would a typical shop have this exhaust gas analyzer?

Thanks.

[GOLDCYLON]

Replace your radiator cap. Possible INJ Housing gasket as well. GC

[WVZR-1]

Hello Yun,

I sent an email earlier than I thought your last post regarding the analyzer! I mentioned that any emissions station would be able to accommodate you. I asked if you used one regularly in VA for other cars. Do you need a shop in McLean or Tysons?

-Dave

[Hog]

[QUOTE=secondchance;175371]

Originally Posted by Marc Haibeck

I like to sample the air in the overflow reservoir with an exhaust gas analyzer. Basically, there should not be any exhaust in the coolant. Detecting over 20 ppm HC is also strong evidence of a head gasket leak.
QUOTE]

Would a typical shop have this exhaust gas analyzer?

Thanks.

You can also by the chemical type gas analyzer's for $20-$30, any auto shop would also have these.

You suck some coolant up through an indicator fluid, and if it detects any hydrocarbons in the coolant, it turns a certain colur.
These kits worked well when I detected a blown headgasket in my 300hp L37 Northstar V8.
Instead of using Helicoils, GM's inserts, or Norms-serts. Their is a guy at Northstar Performance who had engineered a set of 1/2" studs. He pulled the engine up from the top(they are installed from underneath the car) disassembled, machined the block, new gaskets/coolant, re-installed all for $1100.
He lived about 45mins from me, and now he's out West with 3 shops doing this.
Studs work so much better esp. in aluminum blocks. the stud engages the block threads under ZERO stress, then the nut is torqued at the other end. Headbolts are forced to engage threads under both torsional AND longitudinal forces.

The Northstar and LT5 have the same rev range, both were on the drawing boards at about the same time, maybe the Northstar a tad later. The Northstar was in service a year later than the LT5, 1991 vs 1990. I sure wish some parts were interchangeable, such as camshafts. Cams for the Northstar are readily available and are being produced in the aftermarket. The new LT5 camshaft stock is running low, but can be had for around $300 a piece last time I checked.

peace
Hog

[secondchance]

Thanks for all your helpful comments.
I noticed after an extended drive, starting out with the expansion tank and recovery reservoir at normal level, and about 4 hr cool down period, when I undo the radiator cap to the first stage of removal the cooling system seems to depressureize and push air (or exhaust) into the recovery reservoir. This, in my mind, is indicative of pressure build up in the cooling system beyond coolant expansion - almost as though exhaust has gone into the cooling system and this pressurized gas releasing into the recovery bottle. If left alone (not depressurizing by removing the cap, this gas build up would inhibit suction of coolant from the recovery bottle into the expansion tank. Therefore, even when completely cooled visual inspection would indicate 1 to 1.5 gallon shortage in the expansion tank.
Is my assessment reasonably logical?

Injector housing gasket on the offending side was replaced and plenum gasket replaced also.

[Scrrem]

Yun,
Did you pressure test the cooling system?
Rich