How to Check MG ZR / Rover 25 Coolant Level and Condition

How to check your MG ZR / Rover 25 for head gasket failure, the infamous Achilles heel of the Rover K series engines.

I also explain which coolant type to use and how to check the level.


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Time to Complete - 5 minutes

Difficulty - 1/5

Tools and Parts Required

• OAT coolant and antifreeze
• Deionised water
• Funnel

Disclaimer: Any information given in this guide is to be used at the readers own risk. I take no responsibility for injuries to the reader or damage to their vehicles. If this guide is followed correctly, no harm should occur to either the reader or the car.

Please read through the entirety of this guide prior to undertaking any work, and take due care.

Step 1 - Coolant Expansion Tank Location

Locate the coolant expansion tank, it's in the top right hand corner of the engine bay as you're looking at it.

Step 2 - Check Current Coolant Antifreeze Level

Make sure that the car is level, or as level as possible to get an accurate reading.

The Max fill line is the join between the upper and lower half of the expansion tank, the Min fill line is as indicated by the moulded in level line.

If your coolant level is at the minimum, I'd recommend topping it up. If it's significantly lower than the minimum.

Step 3 - Check for Signs of Head Gasket Failure (HGF)

Warning!

Make sure the engine is cold, if the engine is hot the coolant will be too and could spray up causing scolding.

Unscrew the expansion tank cap and take a look inside. Check that there isn't an oily, mayonnaise like residue in the coolant, this is a typical symptom and sign of head gasket failure. The image below shows my coolant, it looks fine.


If you spot mayo in your expansion tank you should do a compression test to confirm if you have head gasket failure.

My car eventually suffered headgasket failure, you can read more in my blog post about how I refurbished the head and replaced the headgasket.

Step 4 - Correct Coolant for the Rover 25 MG ZR K Series Engine

This is really important, make sure you use Organic Additive Technology (OAT) coolant to avoid doing any damage to your engine. OAT coolant is red / pink in colour, if your car's got blue coolant in, like mine did, I'd recommend flushing it out and replacing it, sooner rather than later too.

It's also important not to mix coolant types, if your car has the wrong type, don't just top up with the correct type.

Mine had the wrong type in it when I bought it, and was a likely cause of my radiator failure.

After replacing the radiator I did a full coolant system flush and then refilled with an OAT + deionised water mix.

I recommend picking up concentrated coolant antifreeze, it's cheaper than premixed and will last you much longer.

I've been using Comma coolants for a number of years now, for the Rover 25 and MG ZR K Series you need Comma Xstream G30.


If you do get concentrated coolant make sure you mix it with deionised water, not just water from your tap. The water in your tap has minerals in that could cause corrosion in the system.

Step 5 - Top Up the Coolant Antifreeze

If the coolant needs topping up, i.e. it's at the minimum level or below, place the funnel in the expansion tank and pour in the coolant mixture, or just pour the coolant mixture straight into the expansion tank.

Step 6 - Replace Expansion Tank Cap

When finished, screw the cap on hand tight making sure it is secure.