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Old 04-07-2021, 10:41 PM   #1
240-FAN
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Default B230FT antifreeze leak

This is on a 940 SE that I acquired late last fall. I drove maybe 200-300 miles before putting it in storage. Car did get moved in and out storage twice (turn on car, drive it 10 feet simply in “D” without stepping on the gas and shut her off).

It’s been about 2 months since she was last started. Weather got warm enough this week and I wanted to Take it out for a spin. Instead, I was greeted with a decent sized puddle of coolant under the car.

I already see that it’s leaking from the water pump mushroom seal (yay!), but it’s also leaking from what I think is the thermostat housing. Could it also be leaking from the head gasket?
Oil still smells fresh and anti freeze is clean.





The area within the red marking is what I believe is the coolant leak path. BUT, I haven’t driven the car at anything over 5mph at most when the leak occurred during the last engine start/shut down event. So it baffles me how the anti freeze got that far back if it was just the thermostat seal? It’s bone dry past the temp sensor and knock sensor plugs.


Of course, the water pump.

Any thoughts and suggestions? I was thinking of doing the water pump and mushroom seal (seal from the dealer), doing the timing belt and front camshaft seal (which seems to be seeping) and replace the thermostat and thermostat seal along with a coolant drain and flush to Zerex g05 and get rid of the universal green? Or is universal green fine in these cars (I switched my 240 over to Zerex about 4 years ago)?

Does the leak seem to show anything indicative of the HG?
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Old 04-08-2021, 02:50 PM   #2
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I wouldn't suspect the head gasket yet.

Try resealing the thermostat housing and water pump.

We don't use anything but green coolant in the old Volvos we service unless the customer requests differently.
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Old 04-08-2021, 05:17 PM   #3
dl242gt
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This is a good application for the dye. You can get a UV dye kit from autozone and find out just where the leak is coming from. You can also do a pressure test of the system and see if there is any seepage from that location.
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Old 04-09-2021, 10:23 AM   #4
240-FAN
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Quote:
Originally Posted by planetman View Post
I wouldn't suspect the head gasket yet.

Try resealing the thermostat housing and water pump.

We don't use anything but green coolant in the old Volvos we service unless the customer requests differently.
Gotcha, thanks for confirming the green coolant is fine. For the water pump and the thermostat, should I replace the parts as well since they have to come out anyways?

Quote:
Originally Posted by dl242gt View Post
This is a good application for the dye. You can get a UV dye kit from autozone and find out just where the leak is coming from. You can also do a pressure test of the system and see if there is any seepage from that location.
That's a great suggestion. I was thinking of sealing the water pump and the thermostat first, and then maybe put the UV dye so that it's easier to see where the leak is coming from? My understanding of the pressure test is that it would cause the weak point to leak first and with the water pump mushroom seal leaking at idle and the thermostat housing seeping, it might be worthwhile to fix those first?

For the thermostat, I see that there's a gasket and an o-ring. Can both of be purchased from the dealer? RockAuto shows the o-rings in plenty but the gasket for the thermostat housing seems to be difficult to find?

In terms of general maintenance, the car had it's TB changed in 2015 about 10k miles ago. Since I have to take most of things off to get to the WP, should I replace the timing belt and tensioner as well or is it fine to leave them as is for now? Same thing with the water pump, might as well replace it?
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Old 04-09-2021, 01:26 PM   #5
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Since the water pump and thermostat are coming off anyway, change them unless they were changed recently.

Check the timing belt for cracks and if it's okay, re-tension the belt.
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Old 04-09-2021, 01:36 PM   #6
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I forgot to mention that the thermostat does not use a gasket, only the rubber ring that mounts on the thermostat!!
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Old 04-10-2021, 10:44 AM   #7
240-FAN
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Many thanks Planetman. I’ll get the parts ordered this week and fingers crossed that’ll fix the issues and I can enjoy the new to me car.
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Old 04-13-2021, 10:26 PM   #8
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So I decided to switch the green coolant reservoir cap to a spare black one I had. All of a sudden no more leaks?! It was also 62F outside vs. like 32F that last time I turned on the car which makes me wonder if the cold is causing the mushroom seal to contract and cause the seepage. The green cap says 150kPa and the black one is at 75kPa.

What's the consensus by the gurus here on which cap to run? Is black cap the way to go or should I switch back to the green cap?

Last edited by 240-FAN; 04-13-2021 at 10:45 PM..
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Old Today, 01:32 PM   #9
daniels740
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I run the black 75kPa cap on my 89 740t after my coolant tank burst. No problems thus far. I like to think it keeps me safe from a heater core explosion.
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