Kv6 new thermostat leaks?

Shuriken_57 · 5th May 2021, 22:40

Good morning, gentlemen.
When I fixed my fuel leak, I also replaced my thermostat because it was cracked and leaking.
I did install the new thermostat from dmgrs.
I followed rave procedure for coolant purge.

Yesterday morning , I saw a spot of coolant on the ground.
I checked the engine compartment and to my surprise, there was coolant under the thermostat.
I wondered if I had incorrectly refit the new thermostat . So , I started the operation again.
When I finished the job, I drove with the vehicle, the thermostat works well. I checked the thermostat on the way home and there were no leaks.

Today, I didn't use the vehicle, I inspected the engine compartment this morning and no trace of coolant.
But tonight, I wanted to take the vehicle out and there was coolant on the ground and under the thermostat.
How could the thermostat leak when I did not use the vehicle? This morning everything was clean, I don't understand .
Do you have an idea?
Thank you. ( I specify that I used the keyhole method)

DMGRS · 6th May 2021, 08:02

Hello there, sorry to hear of the bother you're having!
This is usually down to a bit of crud on the O Ring sealing surface in the cylinder block - it can be very hard to clean up / see from all angles, and all it takes is a bit of detritus or pitting and you'll find you get a very annoying intermittent leak.

I'd inspect the mounting hole closely with a mirror to help you see all around it - if you have pitting it can be resolved by carefully refinishing the metal and then using a slightly larger O Ring (which we will of course supply free of charge).

Keep us posted with how you get on - we don't always see posts on here, but you can email us at [email protected] if I can help anymore.

Shuriken_57 · 6th May 2021, 10:25

Quote:

Originally Posted by DMGRS

Hello there, sorry to hear of the bother you're having!
This is usually down to a bit of crud on the O Ring sealing surface in the cylinder block - it can be very hard to clean up / see from all angles, and all it takes is a bit of detritus or pitting and you'll find you get a very annoying intermittent leak.

I'd inspect the mounting hole closely with a mirror to help you see all around it - if you have pitting it can be resolved by carefully refinishing the metal and then using a slightly larger O Ring (which we will of course supply free of charge).

Keep us posted with how you get on - we don't always see posts on here, but you can email us at [email protected] if I can help anymore.

Thanks you. I've do the job twice but it leaking again.
Is it a O rings's problem?

Shuriken_57 · 6th May 2021, 13:00

By the way, the coolant temperature hardly reaches 80 ° and 85 in city. Is this an original mg rover thermostat? with the old thermostat, the temperature was around 90°. The sensor is new.

SD1too · 6th May 2021, 16:00

Hello Brahim,

Sorry if I'm repeating questions that I've already asked you but ...

Did you renew all four 'O' rings?
After assembly did you remember to move the serrated clips on the straight pipe fully outwards?

Don't attempt to fit a larger 'O' ring to the thermostat housing. You will break it (I tried this as part of my thorough investigation of the cause of the leaks).

80 - 85 degrees is much too cool. Either the thermostat is faulty or it's not rated at 88 degrees. A genuine MG Rover thermostat is your best bet.

Simon

Shuriken_57 · 6th May 2021, 23:07

Quote:

Originally Posted by SD1too

Hello Brahim,

Sorry if I'm repeating questions that I've already asked you but ...

Did you renew all four 'O' rings?
After assembly did you remember to move the serrated clips on the straight pipe fully outwards?

Don't attempt to fit a larger 'O' ring to the thermostat housing. You will break it (I tried this as part of my thorough investigation of the cause of the leaks).

80 - 85 degrees is much too cool. Either the thermostat is faulty or it's not rated at 88 degrees. A genuine MG Rover thermostat is your best bet.

Simon

Hello Simon, yes i used the new o rings and i moved the serrated clips on the straight pipe fully.
Where can i find an original thermostat ? It is bad to drive with this thermostat ?
Thanks you.

trikey · 20th July 2021, 10:36

Hello and welcome Aiden, when you get the car, the first thing to do is flush the system a few times to remove as much of the Kseal as possible, this stuff causes blockages in your heater matrix (normally blows cooler on the passenger side when it’s blocked)

Secondly, remove all the thermostat components and inspect them for cracking, age and OAT coolant does no favours to the material that the thermostat housing and particularly the elbow pipe are made from.

Good luck with the car, a days work should see you sort the issue.

Arctic · 20th July 2021, 12:37

Quote:

Originally Posted by biffa75

Simon, great write up and you are 100% correct on the serrated clips providing rigidity to the assembly
Many thanks for this tip that you gave me some months ago!

In regards to the thermostat housing with the four supporting legs... My latest thermostat from summit garage in Dudley that came from x-part that had the saic roewe and mg branding, didn't have these four legs. Being fitted to the car, it didn't appear any less stable than the previous faulty thermostat that had the four legs.

If anything the elbow pipe was less stable than the housing and straight pipe assembly once all fitted nice and snug.

I aren't sure who is actually making the thermostats with the four supporting legs, but my from my latest experience, they aren't made by saic. Do you know who manufactures them? Would be good to get a name.

Rob

Quote:

Originally Posted by SD1too

Thanks for this Rob. I agree with you that correct setting of the serrated clips is the most effective procedure. The four legged versions of the thermostat housing just add a bit of extra stability.

I don't. Mine came from E Car Parts four years ago.

Simon

I went through this when i had my MGZT 190, Simon kindly sent me some O-rings which i fitted to the housing with the stabilising lugs.

I think at the time i was the first to fit this type of housing or one of the first few ? it was still on the car when i let it go in 2018

https://www.the75andztclub.co.uk/for...d.php?t=177152

SD1too · 20th July 2021, 14:15

Quote:

Originally Posted by trikey

... age and OAT coolant does no favours to the material that the thermostat housing and particularly the elbow pipe are made from.

Hi Andy,

I'm afraid that age and OAT antifreeze were the clutches at straws which motivated me to find out the real reason.

My straight pipe is the original, now 22 years old. My curved pipe is 12 years old and I've never had leaks from either of them so the age theory doesn't hold water!

OAT isn't the issue either otherwise my straight pipe would have failed after 22 years exposure to it!

Many more members also use 50% OAT and have never had leakage.

Simon

Aidan Collingwood · 20th July 2021, 15:26

Dear All Members,

Thank you very much for all the welcomes and advice. It's a very helpful and welcoming forum.

I think that for cost reasons, I cannot justify stumping up for a metal thermostat - even if for future peace of mind - if it's just the O-rings which have failed. The cost of metal parts plus the breathtaking year's road-tax for a 2.5 V6 are worth more than double what the seller has been offered by a certain indiscriminate car-buying website, upon whose price I shall nevertheless base my offer to the seller, should I proceed.

To summarize all the advice I've received:
1) If thermostat housing/pipes have not actually failed, suspect/inspect and replace O-rings, and pay close attention to the serrated clips when reassembling.
2) If at all possible, try to get the "four lug" plastic thermostat housing as a replacement if a new housing is indeed required. (Trying to identify and actually buy a suitable thermostat itself seems to be another kettle of worms, but I'm assuming the "four lug" thermostat housing sold in the UK has the correct thermostat inside?)
3) Thoroughly clean the thermostat housing and engine/water pump areas where the thermostat and pipes interface/connect.
4) Flush engine of all coolant several times & check for a balanced performance of interior blower motors; driver vs. passenger side.
5) Keep and eye on coolant levels FOR EVER whilst owning a Rover 75...

Right now I'm also mulling over the "death rattle" that I heard emanating from the top/rear of the engine whilst idling at operating temperature. I've read the buying guides and troubleshooting info on this forum about the possible V6 issues and this car seems to have at least two; the death rattle and leaky coolant in the V... plus a very droopy headlining (Tourer version), door mirrors that don't fully adjust, and the car sounds quite noisy inside whilst on the move which suggests an exhaust leak or a loose metal brace above the headlining. The car has done about 134 000 miles and is being sold by the original owner's wife.

I still haven't made up my mind about buying this car, but even if I decide not to, I hope that this thread serves to clarify the thermostat issue a bit more for other people.

Regards,

5th May 2021, 22:40	#1
Shuriken_57 Avid contributor Rover 75 Join Date: Jan 2019 Location: Freyming-Merlebach Posts: 212 Thanks: 104 Thanked 21 Times in 12 Posts	Kv6 new thermostat leaks? Good morning, gentlemen. When I fixed my fuel leak, I also replaced my thermostat because it was cracked and leaking. I did install the new thermostat from dmgrs. I followed rave procedure for coolant purge. Yesterday morning , I saw a spot of coolant on the ground. I checked the engine compartment and to my surprise, there was coolant under the thermostat. I wondered if I had incorrectly refit the new thermostat . So , I started the operation again. When I finished the job, I drove with the vehicle, the thermostat works well. I checked the thermostat on the way home and there were no leaks. Today, I didn't use the vehicle, I inspected the engine compartment this morning and no trace of coolant. But tonight, I wanted to take the vehicle out and there was coolant on the ground and under the thermostat. How could the thermostat leak when I did not use the vehicle? This morning everything was clean, I don't understand . Do you have an idea? Thank you. ( I specify that I used the keyhole method) Last edited by Shuriken_57; 5th May 2021 at 22:47..

6th May 2021, 08:02	#2
DMGRS Discount MG Rover Spares Rover 75 CDTi, 2x MG ZS180 Join Date: Jun 2011 Location: Hythe, Southampton Posts: 11,320 Thanks: 456 Thanked 3,377 Times in 2,027 Posts	Hello there, sorry to hear of the bother you're having! This is usually down to a bit of crud on the O Ring sealing surface in the cylinder block - it can be very hard to clean up / see from all angles, and all it takes is a bit of detritus or pitting and you'll find you get a very annoying intermittent leak. I'd inspect the mounting hole closely with a mirror to help you see all around it - if you have pitting it can be resolved by carefully refinishing the metal and then using a slightly larger O Ring (which we will of course supply free of charge). Keep us posted with how you get on - we don't always see posts on here, but you can email us at [email protected] if I can help anymore. __________________ Your trusted MG Rover specialist! Tel: 02380 001133 / Email: [email protected] We now have a 'chat' function on our site for even quicker replies. Give it a try! Remember - discount code FORUM5 for 5% off

6th May 2021, 16:00	#5
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,372 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Hello Brahim, Sorry if I'm repeating questions that I've already asked you but ... Did you renew all four 'O' rings? After assembly did you remember to move the serrated clips on the straight pipe fully outwards? Don't attempt to fit a larger 'O' ring to the thermostat housing. You will break it (I tried this as part of my thorough investigation of the cause of the leaks). 80 - 85 degrees is much too cool. Either the thermostat is faulty or it's not rated at 88 degrees. A genuine MG Rover thermostat is your best bet. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

20th July 2021, 10:36	#7
trikey Premium Trader Rover 75 Join Date: Nov 2010 Location: Devon Posts: 33,767 Thanks: 8,837 Thanked 14,831 Times in 8,030 Posts	Hello and welcome Aiden, when you get the car, the first thing to do is flush the system a few times to remove as much of the Kseal as possible, this stuff causes blockages in your heater matrix (normally blows cooler on the passenger side when it’s blocked) Secondly, remove all the thermostat components and inspect them for cracking, age and OAT coolant does no favours to the material that the thermostat housing and particularly the elbow pipe are made from. Good luck with the car, a days work should see you sort the issue. __________________ Lest we forget..

20th July 2021, 15:26	#10
Aidan Collingwood Newbie None at the moment Join Date: Jul 2021 Location: Tonbridge Posts: 6 Thanks: 0 Thanked 1 Time in 1 Post	General Thanks Dear All Members, Thank you very much for all the welcomes and advice. It's a very helpful and welcoming forum. I think that for cost reasons, I cannot justify stumping up for a metal thermostat - even if for future peace of mind - if it's just the O-rings which have failed. The cost of metal parts plus the breathtaking year's road-tax for a 2.5 V6 are worth more than double what the seller has been offered by a certain indiscriminate car-buying website, upon whose price I shall nevertheless base my offer to the seller, should I proceed. To summarize all the advice I've received: 1) If thermostat housing/pipes have not actually failed, suspect/inspect and replace O-rings, and pay close attention to the serrated clips when reassembling. 2) If at all possible, try to get the "four lug" plastic thermostat housing as a replacement if a new housing is indeed required. (Trying to identify and actually buy a suitable thermostat itself seems to be another kettle of worms, but I'm assuming the "four lug" thermostat housing sold in the UK has the correct thermostat inside?) 3) Thoroughly clean the thermostat housing and engine/water pump areas where the thermostat and pipes interface/connect. 4) Flush engine of all coolant several times & check for a balanced performance of interior blower motors; driver vs. passenger side. 5) Keep and eye on coolant levels FOR EVER whilst owning a Rover 75... Right now I'm also mulling over the "death rattle" that I heard emanating from the top/rear of the engine whilst idling at operating temperature. I've read the buying guides and troubleshooting info on this forum about the possible V6 issues and this car seems to have at least two; the death rattle and leaky coolant in the V... plus a very droopy headlining (Tourer version), door mirrors that don't fully adjust, and the car sounds quite noisy inside whilst on the move which suggests an exhaust leak or a loose metal brace above the headlining. The car has done about 134 000 miles and is being sold by the original owner's wife. I still haven't made up my mind about buying this car, but even if I decide not to, I hope that this thread serves to clarify the thermostat issue a bit more for other people. Regards,

6th May 2021, 13:00	#4
Shuriken_57 Avid contributor Rover 75 Join Date: Jan 2019 Location: Freyming-Merlebach Posts: 212 Thanks: 104 Thanked 21 Times in 12 Posts	By the way, the coolant temperature hardly reaches 80 ° and 85 in city. Is this an original mg rover thermostat? with the old thermostat, the temperature was around 90°. The sensor is new.