Coolant Expansion Tank

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The Great White Whale has finally lived up to its name by spouting water all over the place.

Yesterday morning we had to bale out of going to the Fairmile after travelling about 15 miles or so, because the cooling system played a joker, but not in the way you're probably thinking.

The wisdom of fitting an electric water pump is a discussion for another time, but suffice to say that it has served well enough over the last few years, including a hot summer tour in Italy. This was something quite different.

The reason I returned home was because the LED lights on the pump ECU went crazy, the temperature rose and fell, and alarmingly the wiring multi-plug at the pump controller became very hot. Investigation later in the garage revealed the cause of all this mayhem - water in the supply multi-plug to the pump itself.

The plug was duly dried out, sprayed with contact cleaner/lubrication, and the Whale taken out on another test drive which at first appeared to show that the problem had been sorted, but right at the end the fault reappeared. More investigation revealed that not only was the plug soaking wet again, but so was everything around it and below it. This plug is situated in the area below the coolant expansion tank, close to the white seven-way multi-plug that connects the starter solenoid, amongst other things.

At first I couldn't see where the water was coming from, and thought I had another split hose. Further investigation showed that the water was coming from the pressure cap on the expansion tank.

The cap is brand new and it appears that when the spring-loaded seal lifts, that water, instead of flowing down the overflow pipe, is squirting out from under the cap. Because the Whale's coolant system is slightly larger than the standard system, I suspect that the expansion tank is filling right up when the coolant expands, but why is the water squirting out? Maybe a split in the plastic - pressure test called for.

My overflow usually goes down the pipe, Dave, but as you'll see from the photos it wasn't hard to see what was wrong once I'd removed the tank. The damage must have occurred recently and since I last pressure tested the system, as the cap was holding then. I've also just been to North Wales and back without experiencing this particular problem.
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You can see that one of the lugs has split and is mis-shaped upwards, thus allowing the cap to rise and prevent it from seating and sealing properly. At the same time, the 'mis-shaped' lug is also pushing the metal ring out of position.

I hope this helps anyone who might've had similar problems with their expansion tank mod :wink:
 
Phew, for a while I thought he was going to blame the electric water pump, I've had one (electric water pump) fitted to my P6B for a while now and no problems with it, I'll have to post a review sometime for info, I was intending to fit a plastic one myself (when I get one) but the standard overflow expansion is working just fine with a recently refurbished radiator and electric water pump set up. I like the visual check of the plastic ones same as I had in my dolomite and SD1(years ago). but the steel rim did start to rust like the picture, so be careful what you buy I suppose (and buy a spare!) or go the steel type from a austin/morris etc,
Thanks for the heads up LeeEFi

Scott
 
I fill mine from cold to the lower line in the indent. When running normally at 85c the coolant rises to the upper line in the indent.

When queuing to get into a car show last year on a hot baking day, I was there for over half an hour so the engine got quite hot. The level had risen to slightly under the overflow pipe, but no coolant had been released.

Perhaps he has overfilled it, but I have never had a problem with the plastic bottles and much prefer them as you can see at a glance if there is a coolant problem.

Richard
 
I got my metal expansion tank from a land rover wrecker [ breaker] , series 2 I think - Looks the part under the bonnet of a P6b ., whats more it works .
 
quattro said:
I fill mine from cold to the lower line in the indent. When running normally at 85c the coolant rises to the upper line in the indent.

When queuing to get into a car show last year on a hot baking day, I was there for over half an hour so the engine got quite hot. The level had risen to slightly under the overflow pipe, but no coolant had been released.

Perhaps he has overfilled it, but I have never had a problem with the plastic bottles and much prefer them as you can see at a glance if there is a coolant problem.

Richard
Click to expand...

I have to agree with you with the usefulness of the clear plastic type Richard. However, it does appear that they can distort. Rover spec'd the metal expansion tanks for SD1 cars with air-con for some reason. Perhaps they can stand a little more pressure and heat than the plastic type when in use with air-con and in hotter climates?

I've checked my plastic ex' tank on my SD1, and it appears to be ok-ish. Not as bad as Martin's(above pics), but I have been loosing an inordinate amount of coolant in my car, so I've fitted an extra rubber seal on the pressure cap. I now get a tighter seal at the cap, as after a run I get a release of pressure(hiss)as I loosen the cap, whereas before, no hiss.

I have yet to test it out on a full days usage, and on a lengthly run to see how the system performs before jumping to any conclusions. But at this point, it would seem the most likely culprit.
 
westOz74P6B said:
Thanks for the heads up LeeEFi

Scott
Click to expand...

No probs Scott :wink:

It's good to hear from someone else who has an electric water pump fitted to their Rover. We have two owners in the SD1 club who have them fitted. They sound quite impressive with their 'on demand' pumping, and the independant pumping to avoid heat soak etc.

Though one of the owners did get a scare when the in-line fuse melted and stopped the pump working on one of the hotter days a few years back. I think he had to insulate the fuse after that one :idea:
 
GRTV8 said:
I got my metal expansion tank from a land rover wrecker [ breaker] , series 2 I think - Looks the part under the bonnet of a P6b ., whats more it works .
Click to expand...

A Land Rover one sounds like a very good option. I may have to use a metal type if my plastic one keeps releasing all the coolant.
 
View of my set up from a Land Rover, even adapted the L R mounting bracket.

System works well, new 15lb rad cap - no fluid loss over 12 months and easy to see fluid level when cap removed (when engine cold obviously)
 

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