Cooling issue

[Shug]

Okay, it's just started doing this. Under 2Krpm, usually in 4th at 30mph, the coolant temp will rise and rise to over 100 deg, fan kicks in and it'll still not cool. The minute I drop to 3rd and the revs rise, the temp comes down again as the pump flows properly. I've got a PRT stat, but one of the original cream ones, which supposedly had too strong a spring.

Okay, three options.

1. Header tank has a crack, could a lack of system pressure cause these symptoms?
2. PRT getting more cranky as it gets older (on for 30K + miles now) - replace with newer one?
3. (This is what I fear) water pump getting tired, so needs more revs to beat the spring on the PRT?

Views?

[philthy]

could be a combination of all 3 but I reckon the header tank would be the first (and cheapest) to get replaced

[BiggestNizzy]

My header tank was cracked for a while and I had no problems. worth replacing it anyway.

I have one for a rover 200 your welcome to have it, the mounts are different though.

[Rich H]

Remember on the PRT if the thermostat bit opens then the spring bit is closed off.
The spring bit allows flow when the thermostat is not fully open so if you have high revs it allows flow.
Pump could still be fooked though. Isn't it a rubber impellor? Could just not be giving enough flow at low revs full stop.
Pump isn't much harder than a cambelt change is it?


Easibleed on the tank will prove it holds pressure (Or not) Change the tank cap anyway.

Coolant sensor up the duff? Do you have 1 or 2? ( I assume 2 so this would be irrelevant.)

Solution - drive round town in 3rd

Rich

[robin]

Gas in the coolant would cause exactly this issue.

The water pump is designed to rev against a closed stat all day long; the "strength" of the PRT spring is nothing compared to the shut stat that it sees in the OE setup. The two bypass loops (heater matrix and engine bay bypass) make sure that the coolant can always flow so the pump isn't actually that bothered about the stat being opened or closed.

As to how the gas got there ... pipe/rad leak or HGF are the two most common issues.

Is it loosing fluid or ejecting anything from the tank cap?

Bleed it at the rad and engine bay end and see what happens ...

Cheers,
Robin

[hiscot]

I agree with robin i would be looking for a pressure leak or air in the system but regarding the pump the impeller is a design that is only pressed on lightly the reason being that if the engine was ever frozen the impeller would spin on its shaft saving the cambelt and valves ect from damage
i dont think they give much trouble but i always change mine every cambelt change regardless ( for one built in japan )

[Victor Meldrew]

Gas in the coolant would cause exactly this issue.

The water pump is designed to rev against a closed stat all day long; the "strength" of the PRT spring is nothing compared to the shut stat that it sees in the OE setup. The two bypass loops (heater matrix and engine bay bypass) make sure that the coolant can always flow so the pump isn't actually that bothered about the stat being opened or closed.

As to how the gas got there ... pipe/rad leak or HGF are the two most common issues.

Is it loosing fluid or ejecting anything from the tank cap?

Bleed it at the rad and engine bay end and see what happens ...

Cheers,
Robin

That sounds exactly like my problem... i tried to deny it for many months but eventually had admit the HGF had struck again..

[Alex 111s]

Shug, I know how you feel.

That sounds exactly like my problem... i tried to deny it for many months but eventually had admit the HGF had struck again..

Me too. Mine started of by rising temps that would clear with a bit of throttle. gas was getting intot he coolant and vapour locking the rad - in the end, fluid was boiling and rad outlet pipe was still stone cold.

[Shug]

cock....

Will investigate for possible HGF then...

[Rich H]

Sounds like its time for the VVC blanking kit then...

[Shug]

More pressing methinks is getting one of the other collection of sheds taxed and tested before the shugmobile goes up in a cloud of steam...

The old dears are using the Ferrari, so I may get the merc back in the game (getting too close to winter for the Mini)

[Rich H]

Winter project then

[Baggy]

mine has done the same thing since i had the prt (cream stat) fitted and it drives me nuts....no excessive temps...no coolant loss/level fluctuations but air miracuously appearing in the rad. if i bleed it when it's hot it settles down fine and behaves ok but one or two cool down heat up cycles and it's back to as you describe.

In my head, I have the following list of possibles.

leaking bleed valve on rad hose letting air in on cool down
fooked heater matrix doing same thing (did change out heater fan just before prt was fitted).
coolant hose in the engine bay loose allowing air in on cool down.
something funny going on with jiggle valve (but have taken it out fannied about bleeding it and it made no difference so i put it back in.)

[Shug]

Actually, I have had a tiny matrix leak for ages...

[Baggy]

Thing is though, the heater pipes come back the way so that shouldn't cause air in the rad should it???