1991 L400 is leaking coolant again. Mechanic said maybe water pump. Timing belt and pump was changed at 185 kil, car has 230 kil now. Seems a bit soon for the pump to go. No grinding in pump. I'm wondering if the leak may be coming from the water bypass hose at the bottom. Coolant is being sprayed (right hand side - looking in from front of car) at fan belt (top). Can see small leak. Mechanic said $1300 to replace water pump. Anyone ever come across this?

 

My 99 had the exact same issue. The old hose was split on one end under the hose clamp. It wasn't spraying but coolant sludge was accumulating around the clamp. It's a fairly quick and easy fix if your diagnosis is accurate.

 

You've got me hopeful now. The previous owner may have not have checked the hoses while doing the timing belt/water pump. Thanks for your reply!

 

Mine did the same. Hose split at the inlet. Got onto my serpentine belt and ruined it.

 

If your water pump was leaking it would be dripping down from the timing cover at bottom center of engine front, not from where you are describing.

 

Thanks for that info. Not sure what would make it leak around that area. I checked and it wasn't the hose in question.

 

Forgot to add, only other thing I could think of is maybe the copper washer on the coolant temp sensor is leaking.

 

Some pics would help. I know you can't necessarily see the water pump but any pics of expelled coolant would be very helpful.

Do you know the details of the water pump (manufacturer) that was replaced during the TB service at 185K...? If it were a cheap $40 water pump it very well may be on its last leg.

 

A cooling system pressure test may be useful here to find the leak. If the coolant is already drained. You can relatively easily refill it with water during testing while you hunt down the leak.

Also as a data point, on my '91, when the original owner, my father in law owned it, the dealer did the TB service at 90k miles without changing the WP. Then the WP started leaking at 122k miles, which led to a whole re-do on the TB service, along with a new WP this time, and a $4k+ bill.

Is there a chance the previous (one and only ?) WP replacement was not actually done?

 

I've never had good luck with aftermarket water pumps- some lasted and some died and had to do the job again- so not worth it to me.

This little gem is one of my favorite Harbor Freight tools for those hard to find coolant leaks as others have posted will find the leak fast.

 

*Update*

You were right, there was another leak by the timing cover coming down onto fan belt. I just had the waterpump changed no more leak. Only problem now is thermostat is stuck open and the two outer cooling fans are on constantly. Mechanic didn't have time for thermostat. I can change it at work. Just wondering if I change the thermostat will the outer fans stop running continuously? (Note- this is first time I've seen the two outer fans come on)

 

Glad to hear the leak is gone.
Just checking but how did you confirm the T-stat is stuck open? Is the car now not getting to normal operating temperature? If it IS stuck open the engine will not warm up to where it's supposed to be. The way I would confirm the T-stat, if the temp gauge doesn't get to normal operating temp, would be to take out the coolant fill bolt (17mm) on top of the T-stat housing, start the car, (cold) and see if the coolant is flowing. If it is flowing (when cold) then it is stuck open and it's bad.
I don't know how well you know or trust your mechanic but "not having time to change T-stat" while changing the water pump is not right. The T-stat housing is 2 nuts attached to the water inlet housing which is actually removed from the water pump itself. It would take, literally, no more then 2 minutes extra to change the T-stat. As you can see here in step 27 of this; http://www.lexls.com/tutorials/engine/timingbelt.html What I have always done when doing the T belt / WP job is in step 6, instead of removing the radiator hose, I just remove the T-stat housing cuz I always change the T-stat anyway.
I can't answer your question about the fans cuz I've never even seen mine come on in either one of my LSs. I would think they would come on if the car overheats. If your radiator was removed when the water pump was done maybe the fans weren't hooked up right?? Just a thought.

 

Your mechanic must make time for what important to you..
Anyone with an LS400 with an original thermostat should replace it.

DO NOT use aftermarket:

Here is why:

https://www.clublexus.com/forums/ls-...hermostat.html

 

It makes sense that the fans might not have been put back together right. I've never seen the outer two fans come on. On this forum I've heard that sometimes the ground can be loose. The mechanic is a home garage guy he didn't have the T-stat on hand and said I could do that one later at home. He charged 1/3 of reg. price and did it in a day, so I can't complain. After searching I found that the outer fans coming on can be (loose ground), bad temperature sensor, or a bad relay. Not much further to go now and the old girl will be back on track. Hopefully, this weekend I'll have some time to finish. Will post update for anyone else having a 'continuous fan' problem. Thanks for your tip!

 

Thanks for that! The last thing I need is more problems over an extra $20 measly bucks.