90 Ls400 Leaking Coolant From Small Hole Above Crank Pulley

Jim Van · November 22, 2009

1990 LS400, had no heat the other day, and water reservoir was empty, filled both the engine and reservoir, waited till today, good sunlight and time to inspect. After inspecting upper motor, firewall where hoses come in and out, water valve on firewall and from underneath, only place what is coming from is small hole above crank shaft. Assuming that means water pump is about ready to go, but looking for confirmation of my assessment. Also with a 151K on it should I do the timing belt at the same time?

If not wp, as I think, what could it be?

Thanks in advance,

Jim

1990LS400 · November 22, 2009

The water pump on the 1990 LS400 started leaking just before it seized and took out the timing belt at about 75,000 miles in the mid 1990's. It didn't give me much warning ... I smelled the coolant ... heard a clunk ... and the car coasted to a stop -- all in the matter of driving about four blocks from my house on a cold day during a major ice storm. A memorable day since it took a tow truck hours to reach me due to the storm.

Yes, change the timing belt, idler and tensioner when you change the water pump. You might as well since the parts are relatively inexpensive and you are already in there. A failing idler or tensioner can also cause timing belt failure. I've had three timing belt replacements done on two LS400s and the parts I mentioned have been replaced during all three operations -- standard procedure, I'm told.

Do you know if the timing belt and water pump have been replaced? I was told when my water pump failed that the gen 1 LS400 water pump was particularly prone to failure and that the replacement that was installed was of an improved design.

Jim Van · November 23, 2009

1st owner took very good care of the car, timing belt and water pump were replaced at 80k, not sure if by design or was leaking and took care of it at the same time. Glad my assumptions were on it, but as my luck always is, never simple shade tree projects, always the 3 day projects (well at least for me).......