IRomprey

Hello, I have a 1993 Lexus LS400 that has about 152,000 miles.
Recently I have been experiencing some obnoxious shakiness at high speeds, it happens quite randomly.
Sometimes going downhill, sometimes going uphill, sometimes when pressing the brake which I know can be normal to an extent although the shakiness I'm experiencing is a little too much for normal braking.

Not sure what else to say about it, just hoping some of you have had some similar experience and could give me some direction of some common causes.
My dad and I are going to check it out soon but I figured I'd ask here before we got into it!

OTHER ISSUES (Might as well ask on this thread)
I'm having an issue with accelerating and the car feeling like it's going to slip out. Basically, I'll hit the pedal and there is a lag where the RPM goes high and the car is moving slow, not keeping up with the RPM's.
I'm not an expert on cars at all so I'm explaining to the best of my ability. It happens all the time, just about everytime I hit the gas from a slow speed. I have not actually had the car stall or slip out yet, but it damn near feels like everytime I'm hitting the gas there is this insane lag on the acceleration.

The final issue I wanted to ask about (Sorry, lol)
Not sure how big of an issue this is but... I've been ignoring my coolant tank for a long time (Stupid me)
My dad said I needed to flush out my radiator which I haven't done and I told a friend about the coolant situation and we went and bought some coolant. I was checking the tank before driving and for about 3 days straight and putting coolant in if the tank was empty. The fluid went straight into the engine or leaked out very quickly (Maybe 1 day or less) so my friend told me to maybe put a cardboard under my car to see if I could locate a leak if there is one.
Since then, I popped the hood up to put more coolant in and it looks like there is coolant in the tank but it's really black looking. The coolant we bought from the store was green but the stuff in the tank has a very dark color, I have no clue if this is a real issue or completely normal.

Thank you for reading, I appreciate any response greatly

AlaskanLS

Reasons of car shaking in high speed are:
1. Needs to rotate and balance tires.
2. Worn out suspension parts.
3. Bald tires or the wires inside the tires (steel belted tires) gets bent
4. Worn out engine mounts.
Reasons for lag or rubber band effect:
1. Slipping transmission (Worn out parts in transmission)
2. ECU capacitors need to get replaced.
3. Bad ignition coil, spark plug wires, rotors, distributor caps or a cracked spark plug
About the coolant, don't let your car run of out coolant, if you have leak fix it now or later you will blow the head gasket. If you are going to flush the radiator use coolant that is recommended by Toyota. I use Pentofrost coolant. I think it's like 11 dollars a gallon at Autozone.

AlaskanLS

And if your car is shaking while you depress the brake pedal that is the sign of uneven surface of brake rotors. You can take the rotors out and give it to machine shop to polish it to make the surface even or you can get new rotors.

IRomprey

Okay, awesome thank you. @alaskanLS

Regarding the blackness in the coolant tank, is that normal? As long as there is liquid in there I should be okay?

AlaskanLS

Blackness in the coolant tank is the residue of the old coolant that has never been flushed. It may clog the radiator and will effect the engine operating temperature and will cause over heating of the engine and blow the gasket.
Just keep an eye on engine temperature needle as soon you see the needle going up, shut off the engine immediately and don't drive it until you fix the problem.

IRomprey

Got it, the tac has been slightly above the medium line forever until only recently it went JUST a little bit more slightly above the line.
So you would say getting the radiator flushed is a right away type thing to do?
Appreciate the help btw.

AlaskanLS

Flush your car's coolant and replace it with recommended coolant. And rotate your car tires. You can flush it yourself and it's very easy but filling it with fresh coolant, you better make sure you burp the bubbles out of it. If you don't burp the coolant lines then it's heater won't work inside the cabin and you car's engine temperature will get hot and damage it. But if you have no knowledge of what your are doing then you better get it done by a professional mechanic and stay away from jiffy lube or xpress lube.

IRomprey

Okay got it, yeah I went to Jiffy Lube to do an oil change about a month ago. I normally do my oil changes but that's just about all I'm able to do with confidence... lol
They said it would be like $70 for a radiator flush but I'll take your advice and go to a true mechanic.

spuds

Black coolant makes me think someone filled it with stop leak.You should be able to get a new radiator and Toyota red factory coolant for around 100 bucks.Thats how I would address the coolant issue.As noted,an overheat can kill this car.

IRomprey

Okay, you think I should just replace the radiator entirely and get some factory coolant?

spuds

I wouldnt take any chances with cooling on this car.

dlcoffin

add in driveshaft balance, from my own experience, bent or harmonic balance or shaft carrier bearings, are possibilities

billydpowe

iTrader: (1)

IRomprey if you follow the advice in this post you should be fit for a long time..all of it is VERY good

dlcoffin

in my 97 ls400, the reservoir insides have seeminly been dyed red by the coolant permanently. in the shade, looks black due to blocking light.. i use a high power light against the side of the reservoir to check level easier. if i look inside with the light against the side of the reservoir, gives a pretty good indication of what color the coolant in the reservoir is, while looking down in the fill area/cap

Sherl

I second this. @AlaskanLS but would polishing the rotor wont wear out usable surface?