98cherrySS

iTrader: (2)

Vehicle - 98 SS - Mods in sig.

So I'm loosing about a 1/5 liter of coolant every 100 miles or so. Been happening for about a month. I opened the radiator cap and idled it for about 20 minutes last night and I saw some bubbles after the thermostat opened. I suspected the head gastket blew at a coolant passage as there are no puddles under the car.

However there is no smoke coming from the exhaust and no coolant smell anywhere inside or out. The car does not overheat, misfire or drive poorly in any way. All the plugs look identical and are dry (none are steamed). No trouble codes.

I just performed a compression check and here are the results...

Cyl 1 - 180
Cyl 2 - 180
Cyl 3 - 185
Cyl 4 - 180
Cyl 5 - 188
Cyl 6 - 185
Cyl 7 - 185
Cyl 8 - 180

I will mention that I did the waterpump and thermostat a few months ago. I installed a new rad cap and nothing improved. I did a pressure test at 18lbs and it slowly looses pressure. Like 1 lb per hour but then holds pressure after it dropps a couple pounds
I almost feel like the coolant is escaping to the expansion tank and not getting drawn back thru to the radiator. Figured the cap would fix that.

Gimme some ideas guys.

wssix99

iTrader: (5)

Do you just have disappearing coolant in your radiator or disappearing coolant in your overflow bottle, or both?

I'm wondering also if your water pump was a bad one. Was it new or a reman?

98cherrySS

iTrader: (2)

Disapearing from radiator. No loss from the overflow. Waterpump was a new unit from Napa. How would a bad pump lead to internal coolant loss?

DisasterFormula

iTrader: (1)

They start leaking from the weep hole when they start dying.

98cherrySS

iTrader: (2)

I do see a tiny bit of coolant coming from the weep hole. No where near enough to merit the coolant loss I'm experiencing.

wssix99

iTrader: (5)

If you have coolant seeping from the weephole, then that's an indication that the seals are going bad.

The seals hold in coolant but also hold out air. If the seals let air in, you'll get bubbles in the coolant, which settle out in the radiator. The overflow siphon will clear out some air in the system, but when the pump is pumping it in, that's too much for the system to handle and it will accumulate in the radiator. https://ls1tech.com/forums/general-m...ant-level.html

So, you may not be loosing coolant, but could be adding air.

Not sure what your small drop in pressure during the pressure test says. Maybe there are issues in two places?

Brian in GA

My 2004 Tahoe was losing coolant but there were no leaks, none, nowhere. I found GM had issued a bulletin for a hairline crack inside the head between the water jacket and the intake runner. It should have been a recall, a bad aluminum head is no joke but they would have had to replace who knows how many of these, probably bankrupt GM.

Anyways, a bad head gasket or a cracked head or a cracked block could cause this, I doubt it's a block though. I would pull the heads and inspect the gaskets, secondly, have the heads magna fluxed for any cracks.

For what it's worth, my mechanic gave me a price to replace the heads, he knew what it was immediately when I told him I was losing fluid but there We're no external leaks. I went to the auto parts store and bought a small jar of radiator stop leak, the copper metallic kind instead. I stopped losing fluid that day and drove the truck for 2 more years without a problem or addressing this former problem.

Just my 2 cents.

Brian.

98cherrySS

iTrader: (2)

Performed a leakdown test today. All cylinders between 5-10% leakdown.

I drained the overflow and drove about 10 miles. As expected, the overflow now has coolant in it after the drive. I will check it out when it cools and compare how much coolant is in the overflow vs. how much is missing from the radiator.

I am having a hard time justifing pulling the heads with the compression and leakdown results being so good.

98cherrySS

iTrader: (2)

The waterpump may be coming off soon...

Brian in GA

If the leakdown was good I obviously wouldn't pull the heads. It' either going inside or outside, gotta find it boss. Believe it or not, you should call John and ask him if a leakdown would find a bad gasket or cracked head. I would think so but I haven' worked on motors in a while so I can't be sure.

Throw the bottle of copper stop leak in it. I know it's a crappy solution but if it works.....follow the directions if you decide to try it!!

98cherrySS

iTrader: (2)

I'm pulling the waterpump tonight. It's under warranty and I have a legitimate reason for replacing it with the weep hole stain. I'll update on Thursday.

Any other suggestions are welcome.

98cherrySS

iTrader: (2)

I installed the new waterpump last night and drove to work today (about 10 miles). I"ll report my findings tonight.

98cherrySS

iTrader: (2)

Well I've had a busy 10 days and I'm still loosing coolant after the waterpump swap. I also pulled the overflow tank to inspect it and found nothing wrong. I need more ideas. Anyone else experience this kind of issue? I want to pull the heads but I hate to do so with such good compression and leakdown results.

wssix99

iTrader: (5)

Where are you measuring the coolant level from? The overflow dipstick? Or are you looking in the radiator and seeing an air pocket?

98cherrySS

iTrader: (2)

I'm looking in the radiator to check level. Seems it drops about a quarter inch every 15 miles or so. I was thinking that coolant might be getting pushed into the overflow and the vacume was not drawing the coolant back from the overflow. My next move is to bypass the heater core to rule out that part of the system.

Any other suggestions?

wssix99

iTrader: (5)

You can't do this. The system is pressurized and when you open the cap, it will depressurize, break the siphon with the overflow tank, and will have a hard time pressurizing again when you shut the cap with the car warm. (Steam could also form in the system.)

To check the level in the radiator accurately, you need to do it when the engine is completely cool. (At this point, the coolant contracts, sucks in fluid from the overflow and will restore the siphon when it expands again during the next heat up.)

The dipstick in the overflow will give you an accurate reading of the level at all times unless you have a condition that is introducing air in to the system - but to check for this issue, you really need to do it with the car cold.

98cherrySS

iTrader: (2)

I always allow the car to cool overnight before checking the coolant level to allow the siphon process to complete. The vacume is escaping somehow thereby not allowing the coolant from the overflow tank to be drawn back into the radiator.

wssix99

iTrader: (5)

You should be able to check the siphon line with a vaccum pump. If it checks out and you are getting air in the radiator, there must be an internal source - or a bad radiator cap.

Any chance it could be a bad cap?

98cherrySS

iTrader: (2)

Siphon line checks out. My cap seemed suspect. I replaced it with a Stant cap. Oddly this seemed to reduce the amount coolant loss. I still feel the cap may be a problem. Didn't find a hose to bypass the heater core yet. Going to try to do that tomorrow.

wssix99

iTrader: (5)

If its working, it could take one or two more heating cycles to work all the air out.

I'm not a fan of the Stant caps and buy the GM ones. The GM caps have a vacuum relief, (in addition to the normal pressure relief) which protects the plastic parts of the radiator from cracking, should the siphon line get plugged up, etc. I'm pretty sure the Stant's don't have this feature - but they should still work in this case.