Engine Coolant Changed On '99 Ls400

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Car: LS400 Mk4, Year: 1999 (T-Reg)

I changed the coolant on my LS400 today. I’ve changed coolant many times before but it’s the first time I’ve done it on a LS and it took me quite a bit of time to locate the drain plugs. I checked many different parts of the LS400 service/repair manual and I found it wasn’t very clear where the drain plugs were located so I was looking in the wrong places for too long ! In the end I ended up finding them myself.

One thing I liked about this car as far as coolant goes, compared to other cars where I’ve changed coolant, Lexus have placed special drain plugs with small nipples / tubes on the engine so that all of the coolant can be drained. Other cars do have engine bolts for draining coolant, but if the car is more than 4 or 5 years old and you try to open one of these bolts you might end up breaking the bolt since it has seized up, or you get problems trying to seal it back on to the engine block again. What this mean is that you have to make do with draining just the coolant in the radiator.

Anyway if there are other MK4 LS400 owners wanting to change their coolant fluid they might find the below information useful (and possibly save themselves from beating around the bush like I did).

To avoid confusion when referring to position of components (e.g. driver side or passenger side), the below is for a normal UK right hand drive car.

1.) Open the radiator cap on the reserve tank under the bonnet located towards the driver side. This is obvious to spot.

2.) Remove the engine cover and remove the 10mm bolt on top of the throttle body. This is what it looks like (photo below). You will need a 10mm hex key to open this. Be careful not to drop the gasket into the engine bay when you take the nut off. It is best to open the radiator cap and bolt before you start to drain the system so all the fluid can drain with gravity.


3.) There are now 3 drain plugs you have to open in order to drain all 10 or 11 litres of the fluid. One of these drain plugs is the radiator drain plug actually mounted on the radiator and the other two are mounted on the engine.

The drain plug on the radiator is on the driver side end of the radiator. It can be opened from the under the bonnet. When the radiator drain plug is opened, the photo below (take from under the car facing the front) shows the pipe from where the coolant will drain when the plug is opened. Place a container under this pipe. The plug is a normal plastic one and should open without too much force.


4.) DRAIN PLUG ON DRIVER SIDE: Next you will need to open the drain plugs on the engine. I was able to access these by getting under the car. One of the engine drain plugs is on the driver side of the engine. To locate it, it might be easier to follow the long black ribbed rubber boot which comes from the driver side wheel hub, and the drain plug can be seen just above it. This is shown on the photo below. In order open this bolt I needed a 10mm socket and a 11 or 12 inch socket extension. Yes that’s right 12 inches. Be warned: the nut is quite far deep inside the cavity than appears on the photo or even when you actually look at if from under the car. (At this point I got stuck because I only had a 3 inch extension for my breaker bar, so I had to phone a friend to buy me another 8 inch extension from Halfords and bring it round.) I combined the 3 inch with the 8 inch extension along with the actual 10mm socket and it just reached and no more. Even with a flexible joint breaker bar which I had there is not much room for manoeuvre.


Anyway, you might want to attach a piece of hose pipe to the outlet going into a container. I did not remove the 10mm bolt, only enough (a few turns) to let the fluid out of the outlet.

5.) DRAIN PLUG ON PASSENGER SIDE: Now open the drain plug on the passenger side of the engine. It is located in between the cross-member support and the long black ribbed rubber boot which comes from the passenger side wheel hub. This is shown on the photo below. In order open this bolt I needed a 14mm socket, and again, the long socket extension. The access to this bolt has slightly better room for manoeuvre than the driver side. Again, you might want to attach a piece of hose pipe to the outlet going into a container. I did not remove the 14mm bolt, only enough (a few turns) to let the fluid out of the outlet.


The fluid took quite a few minutes to drain and towards the ended it trickled out for 5 minutes or so.

6.) You will need enough contains at the three drain points to take 10 or 11 litres of fluid in total. Once the fluid has drained, tighten all the three drain plugs. The radiator drain plug can be hand tightened. The ones on the engine should be torqued to 12.7 Nm. (I just tightened it with the socket and then gave it a slight nip since my half inch drive torque wrench does not go as low as 12.7Nm.).

7.) Make sure you have 11 litres of pre-mixed red Toyota Long Life Coolant. I purchased 11 litres from Toyota. I purchased two 5 litre cans, (part # 08889-80002 for £17.94 each inc. VAT) and a 1 litre bottle (part # 08889-80002 for 4.34 inc. VAT). Start filling in coolant slowly thorough the filler bolt opening on the throttle body until it becomes full. I filled it up slowly so as not to get any air locks. Towards the end you will also see coolant filling up in the radiator tank. Once full, put the 10mm hex bolt back on and tighten to 45Nm torque.

8.) Top up the remainder of the radiator reserve tank through the radiator cap opening until it reaches the full mark and install the radiator cap.

9.) Start the engine and turn the heater temperature (both driver and passenger temperature) to ‘MAX HOT’. By doing this, it will open the heater water valve under the bonnet. Rev the engine at about 2,000 to 2,500 rpm until the engine is warm. Once the coolant starts to circulate and the engine is warm, the coolant level in the radiator tank will drop. Wait for the engine to cool down again and re-fill the tank to the full mark.

10.) Over the next couple of days of driving you might need to top up the radiator tank if the level drops below full. Always remember to check the coolant level when the car is cold for an accurate reading.

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