freegard

I had a pressure test done this morning on my '94 LS400. I stood there and watched and listened to it. The leak is in the front og the intake manifold but behind the water intake fitting. It is NOT emanating from the rectangular shaped area tha one must seal with RTV or the sealant Lexus dealership sells which is far superior to room teperature vulcanization sealant. It is NOT emanating from the O ring in the water intake fitting; and it is NOT emanating from the plastic thermostat housing. I properly sealed all three of those areas. It is coming from just behing the water intake fitting and under the intake manifold. I can explicitly hear the hissing under 16-18 psi. But I have not had this apart. I have no idea what if any coolant line is there. I would love to get a pdf expanded or blow up of this area of the engine. I would love to know how much work is involved in dismantling the top end to access this leak. All help greatly appreciated. I am an exceptional detail oriented mechanic. Backyard certified! Lol!

No really, I am meticulous but I need to know more because this is my sole transportation, so I want to be right before I begin! Thank you everyone.

steve2006

There is an O ring seal on the rear connection of the water inlet/thermostat housing which may have failed or one of the front water bridge gaskets.
Just seen you have checked the O ring so please ignore comment above.
I will have another look at the exploded diagram sorry I cannot show it due to copyright/legal reasons

steve2006

Had another look and there is a short rubber pipe call water bypass #6 in that location secured by jubilee clips and also a small diameter metal bypass pipe which appears to connect to the rear of the water bridge with an O ring seal.
It may be worth getting one of the cheap CD ROM manuals which normally have these exploded diagrams on as they say "a picture is worth a thousand words"

freegard

I am not sure which rubber hoses you are referring to. Nothing whatsoever connected to the water inlet housing is leaking...including the 3" rubber hose at the top of the water inlet housing and the other short rubber hose on the side of the water inlet housing. The leak is somewhere right under the intake manfold and just to the left and behind but lower than the base of the water inlet housing. As if there is a hose under there that cannot be seen or accessed without removing the intake manifold. And if there is no hose then the intake manifold itself is perhaps leaking...which was all just R&R,d to replace the starter.

It is still under warranty. But I am the new owner. I didn't have the work done. That raises another issue. The warranty does not stipulate that it is not transferable tol new owner. But the shop warranteeing the work states over the telephone that it isn't. I will have to consult state law no doubt.

randal

Have you tried retorquing the manifold bolts? Perhaps one (or more) was not properly tightened or has loosened.

steve2006

You see the thick metal pipe running to the right of the starter motor? That could be your problem but to get to it means removing the intake manifold.

steveski

Sorry to Hi Jack but thanks for posting the picture of the coolant line. I always wondered where it was. I thought it was a rubberized hose like a radiator line. I have an intermittent leak also / very strange and very small. I really hope my leak will be solved when I put new thermostat and housing on the engine with RTV...If not, it is like doing the starter all over again

freegard

Steve2006 and steveski: thanks, I appreciate your help and the photo. Yes I replaced all the RTV (Room Temp Vulcanization) gasket and the o ring and there was a slight leak from the RTV prior to. But unfortunately the leak has not completely vanished. I will be removing the top of the engine to get at the o ring on the pipe that enters the water pump in the above photo. I will replace my coolant temp sensor when I do this as a matter of protocol with 230K miles on engine to ensure that is not my gas mileage issue. It will be fun. For now I leave the reservoir cap loosened 1/8th of a turn which sems to alleviate the pressure, i.e. coolant loss. But I top it off every time I drive it or the heater works erratically...and that also translates to hotspots on the upper intake plenum and possibly the throttle body...which cannot be good for the engine. But until I have the full 12 hour day so I can take it slow and do a good job I will continue to baby her. The guys at Apex automotive that gave an 18 month or 18K mile warranty refuse to fix it--the O ring, though they just xharged the former owner 3800 in fees to replace the water pump and the starter, they won't honor the warranty because the car switched owners. No integrity there. If I performed inferior work I would fix it. But they won't be in business much longer. I drove past and checked them out. A ghostown..no activity. Looks like their ethics are already beginning to catch up with them.
Anyway, thanks guys.

Sincerely,

Tim

steve2006

No problem, pleased to be able to help,keep us updated when you finally get in there and find the problem