ls400nyc

Hi everyone
I am new to this forum
I need some help answering some questions about my 1990 ls400 with 135k miles
I recently drove the car a little too hard
And the back of the engine where the firewall meets seems to be leaking coolant
Took the top of the engine apart and can not find the leak, can’t visually see the leak
However when I put water/coolant in it pours out like a hose
Does any body think it could be the freeze plug?
I can’t see anything from the top and when I’m under the car the exhaust is blocking my sight and the coolant just runs down the exhaust
Does anyone have any clue to where the leak could be coming from?

trukn1

Sounds to me like you may have blown out a rear main seal on the block itself. Hopefully that is it and not a freezeplug.

sonyman

The 1UZ-FE doesn't have any freeze plugs.

ls400nyc

thanks for everyones fast response
so the 1uz-fe has no drain plug huh
hmmm??
for the rear main seal if it was blown would the coolant just leak out slowly or just gush out fast..because when i put water to test it..it cames out rather quick
and if it is the rear main seal ...how hard and how much would something like this cost?

sonyman

The 1UZ-FE has 2 engine block drain plugs, and there is also a drain plug on your radiator. There are no freeze plugs to speak of, however.

19psi

the rear main seal holds oil in, not coolant. check your heater hoses. they go into the firewall. one of the heater hoses has a valve in it that likes to leak, check that. i'ts easy to see, right up a tthe top of the engine, by the firewall.

Bill Dowd

have the parts guy at lexus run you a skematic for the hoses in the car this way you can check where all the hoses are. Also make sure the over flow tank isn't cracked like mine it leaks down by the driver side. a good way to check the overflow tank is stop the motor for a while and use a towel and slowely remove the cap if the pressure doesn't make noise the tank has a leak in it, good Luck

LexLS

It has to be a hose somewhere in the system. As 19psi said, the water valve (bolted to the firewall) does like to leak.

WillieT

I have a 1990 Lexus ls400 with around 300,000 miles just put in a new radiator, new thermostat, and replaced both tempersture sending units to the left of the thermostat housing, because the engine ran hot. I noticed there is fresh coolant leaking and running down the passenger side of the transmission when i start the car and drving along and stop to look under car. None of the hoses connected to the new radiator are leaking. Also notice the resivor tank goes empty when this happens. Seeking solutions to this problem that I did not have prior to the engine running hot. Thanks in advance!

aptoslexus

Check for leak at the water pump.

dicer

Passenger side is where the heater control valve is. It has hoses going to it and a control cable its just above the right hand side valve cover on the firewall check it for leaks. Also there is only one temperature sensor where you described. The other is a temp controlled switch.

python

iTrader: (4)

fix a coolant leak and the weakest link will show up...meaning fix one usually something else fails. i agree heater valve

Clintsuzf

They do have freeze plugs on both heads but only the lower ones have coolant so the top ones dont need to be replced ad they have oil behind them the bad news is that you have to pull the engine to get to them this is my engine from my 92 ls400 i pulled it out today hope this helps

oldskewel

iTrader: (1)

Wow. Great info. The original post was over 10 years ago, but this is good info. Thanks for the pics.

In that pic, is the EGR tube there cracked and leaking, which is a common failure as far as I know. When I got my '91 it had been professionally diagnosed as having a cracked EGR tube, so I bought a new one to replace it myself. After learning how difficult it was, and preparing anyway, I realized that there was no problem and it must have been a misdiagnosis. DOH!