I am not sure I need to do this but it may be helpful in determining whether or not to stick with this car.

This is my girlfriend'* car, and some of you may recall that I recently replaced her cracked radiator -- about a month ago, I'd say. Got a call from her today stating her coolant was gone. I don't know if she drove on an overheated engine or not, but presumably no idiot lights went off. During the week she has a very short jaunt to work from her place, so perhaps it'* unlikely.

I don't doubt that this is probably something mild like a pinhole leak in a hose, or a loose hose clamp (for which I am famous). However, I'd like to know where to look next for major disappearances of coolant if those leads turn up dry. The water pump and its associated bracket were replaced last fall with new dealer items, though I didn't do the work.

It seems that a familiar song is "the ballad of the UIM/LIM" and it looks to me like this is a semi-serious job involving costs potentially in the few hundred range? At that point I think it might be a bit sketchy to do the work on what'* probably a $1000 car, with well nigh 200,000 miles. But you guys may feel differently, or have some idea whether beyond some time, there'* necessarily a lot of investment.

Also, any tips on how best to diagnose the problem if it is UIM/LIM related, or other things I might be missing in my mental checklist for coolant leaks?

Thanks! Sorry for the lengthy post.

What model and year is the car?

If you are losing coolant, and can't find any external leaks, you can be quite sure it is UIM or LIM related. (IMO, If it'* a slow loss, probably LIM gasket...if rapid, could be either...from what you say, sounds like it was rapid; double check on whether the engine light came on)

In any case, that car shouldn't be driven until the problem is found and fixed...if it'* an internal leak, you risk hydrolocking and breaking the crank or connecting rods.
Furthermore, if you want to salvage the car, change the oil right away...do not let the crank bearings sit in coolant-contaminated oil.

A ballpark for a properly done, DIY, full LIM gasket and UIM replacement (on a Series II) is $200 to $250, assuming you've already got the tools and a manual (or at least some very good instructions from this forum).

I consider myself to be not so mechanically inclined and I have done LIM gaskets on my 93 listed below in my sig about 3 weeks ago. Just do it one part at a time and plan it out for 2-days, thats if you take your time and you devote one day to taking everthing apart/cleaning and the next day to assemble everything back together. Its not that bad of a job, and if you dont dick around like I did you can actually do it in one day.

DIY?

All the parts can be purchased for under 200 bucks. Dillon UIM, buttermore stovepipe, Dorman coolant elbow, GM gaskets.

This includes doing the LIM gaskets.

APN upper intake manifold (incl. UIM gasket, .5" stovepipe, and shipping) $115
GM aluminum frame LIM gaskets (GM dealer) $65
Dorman coolant elbows $5
Gallon of "mixes with any type" coolant $8
Blue threadlocker for LIM and UIM bolts $3
Can of brake parts cleaner $3
5 quarts of oil and filter (x2) $30
Craftsman 3/8" drive deflecting beam torque wrench (11ft/lb LIM, 7.5 ft-lb UIM) $25
Rags $5
Total estimated cost $230-$260

If you haven't already done so, please read this article and the attached links: http://www.bonnevilleclub.com/forum/...e=article&k=38

Did mine for about the same money.
Working great 3000 miles in!!!!

Sorry to have lost touch since posting. After she topped up her coolant, the problem has not recurred. I did forget to check the oil for signs of coolant -- I'll try to remember to check it next time around!

I guess the cost isn't too terrible, but even for a few hundred it might be a gametime decision on this car.