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?

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.

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.

planetman said:

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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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?

dl242gt said:

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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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?

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.

I forgot to mention that the thermostat does not use a gasket, only the rubber ring that mounts on the thermostat!!

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.

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?

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.

Thanks daniels740. I'll leave the black 75kPa cap on. I also replaced the fan clutch with a spare "tropical" version that I had. I took the timing belt cover off and the belt and tensioner look to be in good condition. So I'll leave those alone.

I'm about to order the water pump and t-stat for the car.
From RA:
1. Gates 33616 o-ring: $0.54
2. Mahle/Clevite TX12487D 87C t-stat: $11.13
3. Gates 42309 water pump: $21.79
Total with taxes and shipping with 5% off code: $43.77 (WP is lifetime warranty)

FCP:
1. HEPU water pump: $44.29
2. Calorstat 87C t-stat (including the seal): $16.49
Total with taxes and shipping: $74.87

Any advise on if the parts I picked on RA are acceptable?
Irrespective, I'll be getting the mushroom seal and the heater pipe seal/o-ring from the dealer.

Also, on a separate note, how does one take off the ac and alternate belts off? I got the 13mm bolt on the front of the AC compressor and loosened the 10mm tension long bolt, but it won't budge. It's a 1991 940SE sedan

Yeah, the RA parts appear to be correct. The pic of the Motorad t-stat shows it's a reboxed Wahler.

The A/C compressor has a second adjusting bracket behind the first one.

Ha! Admittedly I wasn’t expecting the belts to be setup differently than the 240. Many thanks hiperfauto.

That Motorad t-stat doesn’t show up any more on the RA site. The Mahle/Clevite that I linked above shows to be made in Germany. Is that an acceptable alternative?

Any possibility that you might have similar illustrations for the other belts?

Carquest thermostat from Advance Auto was reboxed Vernet/Wahler. As for water pump I ordered from NAPA (Gates?).

None of the advance autos around here had the parts in stock and the local NAPA hasn’t been very helpful in the past. So I went ahead and ordered the Gates pump along with the Mahle 87c t-stat off RA.

Are there any tricks on getting the water pump and the mushroom seal to seal up correctly? I had a buddy of mine who used to fool a bunch with red blocks help me on my 240. But he’s no longer around thanks to Covid...

The current water pump is seeping fluid out from the mushroom seal under gravity with the car parked. I wiped it off today morning and sure enough there was some anti freeze when I went to check on it some time back.

240-FAN said:

None of the advance autos around here had the parts in stock and the local NAPA hasn’t been very helpful in the past. So I went ahead and ordered the Gates pump along with the Mahle 87c t-stat off RA.

Are there any tricks on getting the water pump and the mushroom seal to seal up correctly? I had a buddy of mine who used to fool a bunch with red blocks help me on my 240. But he’s no longer around thanks to Covid...

The current water pump is seeping fluid out from the mushroom seal under gravity with the car parked. I wiped it off today morning and sure enough there was some anti freeze when I went to check on it some time back.

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I'm sorry for your loss.

From what I learned doing only one pump replacement on a redblock, you want to grease up the mushroom seal nice and good and make sure it seats properly. Once you get it into position, you want to pull up on the pump while you tighten the pump to the block.

To make sure it sealed nice and tight when I installed my water pump, I blew into the coolant expansion tank almost until my eyes popped out, to hear a slight hiss from the mushroom seal. Turns out it buckled, so I put a different one in (ordered multiple just in case) after cleaning the mating surface. I greased both it and the mating surface up REAL good.

It's also good to grease the outside of the o ring that slips into the back of the pump metal transfer tube.


TL;DR: Just grease up your seals really good, pull up on the pump before/while tightening it.

Sounds good. Thanks daniels740. I’m hoping it isn’t too difficult of a job and I’m able to get it back on. Awaiting parts from RA and the local dealer

240-FAN said:

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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The rubber seal should be included with the thermostat.