Coolant leak Heat exchanger

Balders · Apr 5, 2019

Hi All,
I was getting my 2008 F650GS ready to go back on the road and noticed a damp patch beneath the engine and the smell of antifreeze when I started it. On further investigation the coolant level had dropped. After much head scratching I sort of realised it must be coming from the oil coolant heat exchanger somewhere. Gave it a liberal dusting of talcum powder and started it up and ran up to temperature. The leak looks to me if it is coming from the seal where the exchanger mounts on the engine. After a ride of 90 miles the coolant level only dropped slightly. Any advice on where the leak would be coming from would be gratefully received.
Balders

Hoff · Apr 5, 2019

On my 700 the heat exchanger is bolted to the front of the engine with a preformed seal between the engine and heat exchanger. RealOEM shows the seal as item 2.
I hope this is of some help.
Paul

Hoff · Apr 5, 2019

Just looked at realoem for the 650 and the setup is the same, part numbers are also the same.
This might be helpful!!

Balders · Apr 5, 2019

Thanks Hoff,

I will have to add a new seal and some O rings to my next Motorworks order. Would it be advisable to apply some kind of sealant when re-assembling the heat exchanger?

Hoff · Apr 6, 2019

Not sure on this but I am sure someone else may be able to help on this one.

Balders · Jun 7, 2019

Fixing it

Hello again,

Well I finally got sick of the sweet smell of hot coolant coming from the bike. It was not loosing much water just a little dampness on the gasket seal.
When I got the heat exchanger off, I had high hopes of an easy gasket change and a weekends riding. Unfortunately the exchanger has rotted leaving the gasket face completely ruined. :blast

Oh well new one ordered and now a weekend of alcohol abuse to look forward to. :augie

Balders · Jun 7, 2019

Moral of the story don't just order the gasket the dammed thing is probably leaking because it is corroded.

thomo57 · Jun 9, 2019

Balders said:
Moral of the story don't just order the gasket the dammed thing is probably leaking because it is corroded.

Hi Balders, have a similar leak on my ‘09 F800, noticed it for a couple of months, just been keeping an eye on the expansion tank level and the occasional top-up. Bikes on 93K miles and I’m planning to give the engine/frame a good dose of TLC over next winter, when it gets to 100K as there’s some frame corrosion I need to sort and the timing chain rattle is bugging me, despite the custom ear plugs

Good luck with your repair, how much was the replacement cooler ?

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Balders · Jun 9, 2019

Hi Thomo,
The cooler was £117 from Motorworks. My bike has only done 34K and the timing chain rattle for the first couple of minutes after starting was beginning to concern me. I have replaced the cam chain tensioner plunger and spring. I will let you know if it quietens the rattle. If you need to replace the cam chain an absolute hero has come up with an alternative to splitting the engine.
https://www.youtube.com/watch?v=sZbnuXugS-s

daveg · Jun 19, 2019

Balders said:
Hi Thomo,
The cooler was £117 from Motorworks. My bike has only done 34K and the timing chain rattle for the first couple of minutes after starting was beginning to concern me. I have replaced the cam chain tensioner plunger and spring. I will let you know if it quietens the rattle. If you need to replace the cam chain an absolute hero has come up with an alternative to splitting the engine.
https://www.youtube.com/watch?v=sZbnuXugS-s

Well, I just checked in to search 'coolant leaks' and saw this thread. My 2008 F800GS with about 30k miles has been weeping liquid which I just realised is coolant. I was waiting to see where it was coming from after cleaning the bike and thought I'd just have a look on here on the basis that most faults are fairly consistently common. The heat exchanger does look a bit corroded around the gasket so I expect it's that. I assume the coolant spreads around the area when the bike's hot because it's not obvious where it's coming from at the moment?

daveg · Jun 20, 2019

daveg said:
Well, I just checked in to search 'coolant leaks' and saw this thread. My 2008 F800GS with about 30k miles has been weeping liquid which I just realised is coolant. I was waiting to see where it was coming from after cleaning the bike and thought I'd just have a look on here on the basis that most faults are fairly consistently common. The heat exchanger does look a bit corroded around the gasket so I expect it's that. I assume the coolant spreads around the area when the bike's hot because it's not obvious where it's coming from at the moment?

Update as it might be of interest. I went for a 10 mile blast including motorway to get it hot and so far there's no leak or weep visible. The coolant is at the minimum mark, I'll not top it up, just keep an eye on it in case it was the overflow.

thomo57 · Jul 11, 2019

Sorted my oil cooler leak, new cooler and seal fitted this morning, hopefully good for another 94k Miles

,

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Cymrocoll · May 8, 2023

Hi All, Having had a very similar coolant leak around the heat exchanger on my 2010 f650GS, I took it off to find a very similar amount of corrosion to these images. I ordered a new heat exchanger and rubber gasket, but once I put it all back together and put in new coolant, it was still leaking. I saw that in the image above that a blue sealant had been used, I didn't think it should be needed with the rubber gasket, but I decided to try again, this time with sealant. As soon as I came back from my first short test ride, it was leaking again. I've now bought a better quality Loctite sealant and another rubber gasket (as well as yet more coolant!), but have no confidence it will work this time.

One thing that strikes me is that, as per the images above, there are only 4 holes on the back of the heat exchanger, but 5 holes on the engine. The middle hole therefore doesn't line up with anything on the exchanger, Is this how it should be? Oil splills out of the middle hole when I take the exchanger off, so it must have some sort of use, but that oil has nowhere to go? I threw away my old exchanger before noticing this, so can't check if the original was the same, but I don't recall any differences when I compared new and old initially.

Any advice welcome, as I'm stuck without a bike until I can get this resolved. thanks.

Coolant leak Heat exchanger

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