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Discussion Starter #1
Hello everyone, its been a while since I've posted. Haven't had any real issues. But now I have head scratcher! I recently had an opti-spark failure (no suprise there), after replacing it my coolant would disappear. Rad low enough to turn on "low coolant" warning light but reservoir was full. Pressure checked system found crack in rad side tank. Replaced Rad. After all that still losing coolant. Under pressure with tester losing about a pound every 15 min. There is no sign of a leak, carpet inside is dry, no sign of weep hole on pump leaking. The reservoir is full and the recovery system is bypass while testing. After multiple attempts to find the issue I concluded that the coolent must be entering into a cylinder, and changed the oil to confirm. There was no coolant in the pan eventhough I had about 2 quarts used in the testing. It's a 93 TA, rebuilt 13k miles ago all new accessory components including WP. Anyone have any ideas on how to further diagnose the problem? I don't really want to start throwing money at it, the heater hose alone is 200 bucks.
 

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Since coolant getting into cylinders doesn't always put coolant in the oil, you should look for white smoke from tailpipes and feel inside tailpipes for oily feel of coolant.

Have you checked the steam pipes at back of cylinder heads for leaks?

Also run engine with rad cap off. Once thermostat opens look for bubbles in the coolant. Do a compression test to see if head gasket is leaking.

Pressurized cooling system normally leaks down pressure after engine is shut off. That's why you can remove rad cap after engine has cooled off, without a spray of water coming out.
 

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Discussion Starter #3
Thanks for the reply, I have looked for smoke, smell and felt for any signs. Came up with nothing. Pressure test was cold and turned over engine to make sure the approximate 2 quarts of fluid lose wasn't left in the cylinders. I have found that after driven much of the coolant is found in the reservoir but there is a leak somewhere that allows air into the system and doesn't pull it back from the reservoir. The pressure test shows a leak but no sign of it. I've heard of deteriorated lines collapsing and creating a valve like block allowing flow in one direction but not the other. Considering that this is the case, not leaking visibly but pulling air when cooling. Thoughts?
 

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I think I may have the same problem. There is a little bit of discoloration at the water pump weep hole and I haven't done a pressure test. I suspect a blown head gasket as #3 & #5 cylinders read compression at 180#'s where everyone else is 170-175#'s. That was a few years ago with only a little water missing from the reservoir. It's recently gotten very noticable.
 

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Thanks for the reply, I have looked for smoke, smell and felt for any signs. Came up with nothing. Pressure test was cold and turned over engine to make sure the approximate 2 quarts of fluid lose wasn't left in the cylinders. I have found that after driven much of the coolant is found in the reservoir but there is a leak somewhere that allows air into the system and doesn't pull it back from the reservoir. The pressure test shows a leak but no sign of it. I've heard of deteriorated lines collapsing and creating a valve like block allowing flow in one direction but not the other. Considering that this is the case, not leaking visibly but pulling air when cooling. Thoughts?
After replacement of radiator and cooling system was top off.was the system purge of air. Sometimes when cooling system is opened and drained for repairs it is possible to trap air.When system is refilled you can open the bleeder valve to remove trapped air. The valve on the engine, not on the radiator.When coolant is running out of bleeder close the valve and top off system and reservoir.Start and run to engine temp.and cooling fan comes on stop's.Shut down and let cool off.When cooled off check the reservoir level.If it checked okay remove radiator cap and check level of coolant, should be at the very top of the radiator.Hope this helps.
 

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Discussion Starter #7
I've done that multiple times, when pressurized cold and when running hot (at least operating temp).
 
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