Rover 75 2.5KV6 Losing coolant
 

2001 75 60k miles, consistently loosing coolant. Initially there was no evidence of leak or where it was going until it started pouring , dripping from oil filter area. Garage ( Jaguar specialist ) pressure tested over 2 days , couldn't replicate the leak. Looking closer, the V between the cylinders is absolutely swimming in coolant. Temperature sensor caked in corrosion. Not looking forward to removing that.

Cambelts, water pump, thermostat all replaced by said jaguar specialist (£1500 ) less than 1000 miles ago.

Welcome any comments. About to take inlet manifolds off.

Thermostat must be the no1 suspect - maybe the new one has split.

£1,500 for cambelts, water pump & thermostat is daylight robbery :eek: (unless they did other work too).

Hello Digby,

This will be coolant loss in the 'V' due to shrinkage of the 'O' rings, particularly that at the base of the thermostat housing.

If you remove the plastic manifold chamber then the LH bank aluminium manifold you'll be able to remove the three plastic coolant components by levering very carefully underneath the fixing flange of the thermostat housing. First though, note the position of the two serrated clips on the straight pipe. Are they touching the water pump and thermostat housings? If so, slide them inwards before attempting to remove anything. The curved pipe is the most fragile of the three and if you're lucky you'll get it out without breakage. New 'O' rings are CDU 3858. There's no need to renew the entire assembly but many people do.

After reassembly, make sure that you slide those serrated clips outwards so that they're hard up against the water pump and thermostat housings. It's this positioning which makes the assembly absolutely rigid and prevents future leakage. Mine's been bone dry for several years now. Take no notice of a well-known and notorious member's efforts to belittle this simple remedy, should he appear on this thread.

Simon

PS 60,000 miles is about right for this problem to occur. There's no need to remove the temperature sender.

O rings here if you need them - https://rimmerbros.com/Item--i-GRID001716

Hello Digby, while there may be "evidence" SD1too believes to be true that mechanical abrasion is the causal effect of O ring failure, this is a known failure mode on other MGR models employing the exact same O ring as used in the KV6 thermostat assembly, hence invalidating his theory.

For the lowdown on the actual failure mode, you may wish to follow the link in my signature, where you will find compression set is the actual cause of failure.

For others who may be interested, I have attached the original AR specification and drawing for CDU3858, in order that you may obtain a Viton O ring of the correct dimensions.

I won't bore you with the details, however my background is a electro-mechanical design engineer, specialising in factory automation, and a particular bias in the disciplines of pneumatic and hydraulic control.

Now you can imagine I have seen quite a broad and varied range of mechanical seal failure, and investigated the causal factors in some depth, and O rings suffering from compression set are no longer round in section, instead they appear to be a flattened oval where the material has taken on the form of the groove the o ring is positioned in.

This is the exact failure mode I have witnessed in many cases of the O ring in question, when employed not only in the KV6, but also the four cylinder K series.

Simon can base his findings on one car, and as such has a limited subject sample to draw upon, and while he may be correct in assuming the O rings are at fault, he is most certainly incorrect when assuming the failure is caused by mechanical abrasion.

So what it boils down to in the end, do you trust the opinion of a vision mixer who has worked on one car, or the time served engineer who has worked on many more than that.

Brian (The Notorious Member)

And... You don't need to remove the inlet manifolds to change the thermostat and other pipework, it can be done by removing the throttle body and accessing from the side.

Jag garage : belts , thermostat , water pump + service ( although didn't change spark plugs ) and MOT.

I had to sit down and practice deep breathing when they gave me the bill & they had the car for two days. I wouldn't have used them if I had had any idea they were gonna charge anywhere near that. They were always so reasonable with my XJ12 . Lesson learned , never mind.

Ooh, XJ12, one motor I wouldn't say no to.

Don't forget, you can ask about any specialists recommended by members for future work.

Before further suggestions are made let us know what you find when you take a look.

Trikey : well I've got nothing else to do so I thought I'd replace all the gaskets and O rings plus change the spark plugs - the back ones should be easier to get to. I may also steam-clean the engine bay and clean and treat the leather.