Could it be the rad cap?

[Tiger Tim]

Hi All,

Took the MR2 for a spin last evening & the temp gauge went up to the edge of the red. Before I set off, I noticed the level in the expansion bottle was about 1 inch above the max. Had it for a 120 mile spin 2 weeks ago so must have gone up then. I had the bottle out to clean over the winter & filled to the max level then but did not bleed the system. When it got hot last evening, the bottle was almost full. Turning on the heater brought the temp gauge down. Both pipes going to/coming from the radiator were hot. The coolant never returned from the bottle to the cooling system. I thought it was just the gauge at first as when I checked the connection, it was a bit loose & occasionally, the guage came back to normal. The cap on the expansion bottle is on correctly & the moving bit on the rad cap moves freely. Any ideas?.

Thanks,

Tim

[Tiger Tim]

Going to get a rad cap from Mr T today. Might as well get the cap for the expansion bottle as well eventhough it looks perfect.

T.

[alfiembra]

I've been having recent problems with gurgling and bubbling in the expansion bottle after switching off the car but not had any overheating while running. I changed my cap last weekend and so far (touch wood) no more noises, don't know how old the original cap is it's been on the car as long as I've had it so could be 10 year old at least. The new cap I got from a motor factors and it was noticably tighter to fit on the neck of the filler.

Alan

[cartledge_uk]

I once heard a rumour that the cap on the expansion tank is one way (valved) maybe worth checking (mine isnt hence the rumour)

[PW@Woodsport]

You're not wrong Tim, if it's put on back to front you get coolant loss and overheating, they are very much one way fitment only.

[Tiger Tim]

Cap on the expansion bottle is definitely the correct way around. Could I have caused some type of air-lock by taking out the bottle to clean?.

Tim

[PW@Woodsport]

No, that's not possible.

[Tiger Tim]

Thanks, Paul

Will fit new rad cap & new cap for expansion bottle & bleed it. Not sure what caused the water to fill the bottle & not go back. Has been perfect for the past two years in that department. Hope the bleed sorts it.

Thanks,

Tim

[Tiger Tim]

Got a new rad cap & cap for expansion bottle (robbery ftom Mr T). Bled the system & started the car. I think (hope) there may be something wrong with the guage. The needle came up to half way within a minute & then to the red a few minutes later before the coolant got really hot. Once the thermostat opened it dropped to about 3/4 but back up to the red within 1 minute. Taking the connection off the sensor on the block (the one above the alternator & in front of the expansion bottle) only dropped the needle to half way. I thought it would just drop the needle to zero !!.
Went out to the garage this morning before work to check again. Turning the key on without starting brought the needle up to about 1/4 eventhough the car was cold all night. I turned the ignition key from outside but the car didn't start as I need to give it a bit of accelerator as well. Now with the car just turned over once & not running, the needle was up to 1/2 way. Removing the wire from the temp sensor didn't cause the needle to drop. Could the guage be faulty or going to earth somewhere.

Thanks,

Tim

[Tiger Tim]

Got a replacement set of dash clocks & swapped over the temp guage. Problem sorted.

Thanks.

Tim