1995 Buick LeSabre unexplained coolant leak

[tken35]

My mechanic replaced the water pump about three weeks ago and this seemed to help slow a coolant leak. Unfortunately, I am still adding about a quart of antifreeze to the reservoir every week. He did a pressure test the other day and stated that everything was normal and that there was no contamination in either the oil or transmission fluid.

I have spent the last several hours reading many of the post regards leaks, intakes etc... but now I am more confused. My main concern now is what BNaylor says in one of his posts on 12-29-2008, "RE:98 buick lesabre upper and lower intake" (sorry don't how to link) about "hydro-lock".

The car only has about 70,000 miles (but the engine was replace with a rebuilt one about 30,000 miles ago).

I don't want to go the route of adding some sort of stop leak (ie, Bars, tablets), I would rather resolve the problem.

So here are my questions:
1) What are the experts suggestions?
2) What is the difference between a UIM and LIM?
3) Should I have both replaced?
4) What other parts if any are needed?
5) What parts/manufacturer to avoid (some posts noted that you should only use GM metallic LIM??)?
6) What is book hours to perform this job?

Thank you in advance.

[ilco187]

i dont know about the intake but it could be a slow leak going into the cylinders and burning it off, which would be a bad head gasket.

[HotZ28]

First of all, if you have a 1995 LeSabre, your engine would be a VIN-L engine (8th digit of VIN) which does not have the Series II VIN-K UIM "EGR burn-out" problem. In addition, head gasket failure is very rare on these engines; in fact, I have never seen one with a "blown" gasket. You sahould disregard all information concerning the VIN-K engine UIM problem, or blown head gaskets on your engine!

So now what could be your problem? I would suspect a hair-line crack in the plastic radiator tank, or LIM gaskets. Your car is at the right age for radiator tank failure and this can be hard to diagnose because the crack is usually very fine & the leak will barely show up with the engine warm, or with a pressure test. In addition, the leak is usually @ the top (driver side) or the plastic tank, (may be covered by radiator support cover) and as the coolant drains down the hot radiator, it will burn off, leaving no signs of dripping. A good way to check for this leak is to place a clean/dry piece of cardboard on the ground underneath the front drivers side radiator & let sit all night (engine will cool down) and check for signs of coolant in the morning before starting the engine.

[tken35]

Thank you for the responses! I will place a piece of cardboard underneath the car tonight when I get home and post the results.

Given the age of the car, would you recommend (as a precaution) replacing the radiator even it turns out not to be the problem?

With regards to the LIM, are these the gaskets? The reason I ask is that when I called O'reilly's they stated that they don't have a LIM, but did show 615-179g (gaskets) or 615-179 (Intake manifold kit - including all gaskets and seals).

[HotZ28]

You do not need an LIM, (or UIM) all you would need is an intake set (if that is the problem) Yes, due to the age of the car, a new radiator would be cheap insurance! Check RockAuto for best price. They have several for $99.00 - $115.00 ea. Once again, do not get confused reading post about UIM failures on Series II Vin-K engines, if original, that is not the engine you have!!

[inafogg]

i'd agree with hotz if the engine was new 30k ago i hope there's no engine issues.
there is a dye you can add to coolant drive a day or so & check for a leak under a black light good luck