MR2 Roadster Owners Club

The Workshop => Maintenance, Problems & Troubleshooting => Topic started by: Rushy67 on August 3, 2026, 13:38

Title: Coolant loss
Post by: Rushy67 on August 3, 2026, 13:38
I am custodian of @greybeardgt blue roadster which i have had since 2019, those of you that know the car, will know he looked after it superbly, i have continued to do so.
It is a low mileage example less than 40k with very regular maintenance.

When the car has been standing for 3-4 days i have a coolant loss of approximately the difference between the hi and low levels on the reservoir.

It had new Toyota radiator and hoses 4 years ago and my local garage has pressure tested and checked all hoses whilst car is on the ramp. They did a 30 mile road test and could not see a leak.

I have just replaced the reservoir cap with a Gates one, should i have got a genuine toyota cap?
Would the actual reservoir have a leak?
There is no presence of "wetness" anywhere around it.
Title: Re: Coolant loss
Post by: Carolyn on August 3, 2026, 15:57
It could be coming from the water pump. The drip would end up on the undertray and then evaporate.

It's only a 'could be'.

Title: Re: Coolant loss
Post by: Rushy67 on August 3, 2026, 16:19
Thank you, will investigate this
Title: Re: Coolant loss
Post by: Rushy67 on August 3, 2026, 18:26
Quote from: Carolyn on Yesterday at 15:57It could be coming from the water pump. The drip would end up on the undertray and then evaporate.

It's only a 'could be'.
Carolyn, can i also add that temperature gauge does not move from half way even on a spirited 200 mile drive.
But coolant loss is noted once car has cooled.
I have lost about 500ml in 600 miles of driving.


Title: Re: Coolant loss
Post by: Gaz mr-s on August 3, 2026, 19:45
Don't rely on the temperature gauge.  If it moves upwards of 'normal', it's 'Oh shit' time.
Title: Re: Coolant loss
Post by: SurreyMR2 on August 3, 2026, 19:49
Mine was losing coolant when temp 30+ but absolutely no sign of a leak anywhere!

Radiator replaced 2 years ago, water pump last year & system bled as per all the guides. Coolant level would stay level unless exterior temp was 30+ and then it would drop without any evidence  >:(

I had tried 2 caps, the one that came with car so probably a 2001 cap & another that came with my replacement 2006 engine so a bit newer but same fault with both. On suggestion from another mk3 driver that I try a new one anyway, I did with a new blueprint item that I had in my spares and my coolant has been level since.
Title: Re: Coolant loss
Post by: Joesson on August 3, 2026, 20:04
A leaking water pump was mentioned in the Mr T service notes that came with my 2002 2 when I bought it in 2011.
It was also mentioned, again by Mr T when I had a first service with them. No mention of it in either two or three subsequent and I couldn't find any trace of a leak when I took over the servicing myself.

My daily Ford is North of 100k and when I had the cam belt changed the Ford recommendation was to have the water pump changed.
The Service Manager , son of the Main Dealer owner. didn't agree , saying he had never had to replace a water pump on that engine type. Coming up to a second cam belt changed, might have it given a good looking at this time.

I rather like the @SurreyMR2 suggestion of replacing the radiator cap. That was  not uncommon to hear of in the 60's .
Title: Re: Coolant loss
Post by: Ardent on August 3, 2026, 20:57
Quote from: Gaz mr-s on Yesterday at 19:45Don't rely on the temperature gauge.  If it moves upwards of 'normal', it's 'Oh shit' time.
+1
Once up to temp, the 3 o'clock position, it remains rock solid. Fans can come on, but the needle does not move.
@SurreyMR2
Plugging in an obd dongle will reveal the true temps. They do move up and down. Just not the needle.
Title: Re: Coolant loss
Post by: Hawko on August 3, 2026, 21:41
Quote from: Gaz mr-s on Yesterday at 19:45Don't rely on the temperature gauge.  If it moves upwards of 'normal', it's 'Oh shit' time.

As someone once described the Celica temperature gauge it three position, Cold , Normal, Fire
Title: Re: Coolant loss
Post by: Chilli Girl on August 3, 2026, 23:08
Chilli my facelift 2002 had a supposed leak mentioned once or twice on its vehicle check. I never noticed anything in 9 years of ownership and to my knowledge is still the same!
Title: Re: Coolant loss
Post by: Ardent on August 4, 2026, 20:40
Quote from: Hawko on Yesterday at 21:41As someone once described the Celica temperature gauge it three position, Cold , Normal, Fire
That made me smile.