Coolant Hose Blew off Thermostat? 2009 XC90 3.2 AWD, 99k miles

[31years]

Hi, Folks,

Pretty new to the forum, but have owned / wrenched Volvos for 31 years and could use a hand.

As you can see from the pic, the top end of a coolant hose blew off the thermostat tonight. Thankfully, this happened just as I pulled into my driveway. Yes, I am a lucky guy today.

After reading everything I can find on this forum, I'm apt to replace both the hose and the T-stat.

I have the following questions for you all:

- Does anyone have an idea of what's happened here? Is it simply the dreaded T-stat failure that has been written up plenty of times as a common issue?

- Should I replace anything else (it has a new Serpentine Belt, Alternator, Alternator Pulley and tensioner in the last 3k miles)

- Am I totally off and should be worried about something else?

Thanks so much for any help!

Brian

[oragex]

.
I will assume it's not a problem with the head gasket (but worth looking at the remaining coolant for any oil contamination)

Can you see on the hose if it's a genuine Volvo ? Aftermarket ones are known to be low quality. I see it has the genuine Volvo clamp which is good to prevent self-loosening. A little surprised you didn't notice leaks at the junction the days before. Makes me think there was a lot of pressure inside the cooling system. A certain amount of pressure is necessary, but it looks like it went way past that. Have a look or replace the coolant reservoir cap (the green thing). These must have an 'oeverpressure' release valve, which may be faulty. You can also 'feel' in a way the pressure by trying to squeeze the upper hose with the engine fully warmed (with some thick gloves or a rug). You should be able to squeeze the hose without too much force - if however it feels like rock stiff, then perhaps there is too much pressure inside the system - either the cap has a problem, or, I'm thinking the system was 'burped' too much to the point there were no pockets of air remaining for expansion - and perhaps the coolant tank was also overfilled

Your 3.2 has also a funky thermostat unit. These have some small plastic 'legs' inside that like to break all of a sudden, causing sudden engine overheating this may be another explanation. At 99k miles is the best moment to replace it - not cheap, but at 10 years it's about the time for it. Recommend buying genuine one. For the coolant, I suggest using distilled water mixed 50/50 with concentrate from Volvo - it is very well priced (for once) https://www.fcpeuro.com/products/volvo- ... 89#fitment

The water pump on these engines also seems to be a problem https://volvoforums.com/forum/volvo-xc9 ... ses-79115/

.

[31years]

Thanks, Oragex. I've added a new cap to my shopping list.

I agree that the pressure must have been very high in order to blow the (OEM) hose off the Thermostat. Could a failing T-stat caused that?

The coolant looks fine - not oily at all. And the car was driving fine right up until I parked.

Finally, do you mind explaining your thinking on the water pump and how that could factor into this situation?

Brian

[KurtL]

My daughter’s 2001 V70 kept blowing off the top radiator hose. The dealer did a pressure test on the cylinders and it turns out the cylinder was leaking through the head gasket into the coolant building up pressure and blowing the hose off.

[oragex]

Not directly relating the pump, linked because it seems a common fault occurring relatively early, worth checking while there

[31years]

My daughter’s 2001 V70 kept blowing off the top radiator hose. The dealer did a pressure test on the cylinders and it turns out the cylinder was leaking through the head gasket into the coolant building up pressure and blowing the hose off.

Kurt, was that engine a 2.5 or a 3.2?

[xHeart]

It looks the hose was never fastened properly OR the clamp has malfunction. Oragex's suggestions for maintenance is spot on.

This discussion may help viewtopic.php?f=10&t=87254

It is hose #38 in this diagram:

[31years]

Thanks to you all for the great tips / direction. I have the following coming to me on Wednesday (should be a nice Thanksgiving in my garage):

- Thermostat Unit
- Coolant Hose
- Water Manifold O-Ring
- Hose Clamp
- Cap
- Genuine Coolant

My hope is that simply re-clamping the hose would do the job, but it looks like I might as well replace the T-stat unit while I'm there.

I'll let you know what happens.

Brian

[gstallons]

# 1 the outlet the coolant hose attaches to looks to be ribbed . Are these ribs in good condition ? If not replace it . Now I keep spring type hose clamps in stock for most all size heater , radiator hoses . I prefer them over anything else . These maintain CONSTANT tension . I've seen water outlet , t-stat housings and just about anything plastic carrying hot coolant fail over time . Do not be afraid to be liberal and replace anything you think is necessary .
Good luck !

[pgill]

A link with some pictures

https://www.freel2.com/forum/topic32245.html

Let us know how it goes

Thanks

Paul