Upper radiator hose collapsing


Asked by Jul 09, 2013 at 07:24 PM about the 2005 Pontiac Bonneville SE

Question type: Maintenance & Repair

I changed the thermostat, gasket, both radiator hoses and flushed the radiator but the upper hose collapses when the car is cooled down....It fills up when motor is running and does not over heat

21 Answers


Check the hose going to the overflow bottle and the radiator cap. The oevrflow hose may be blocked or the radiator cap may not work as advertised anymore and is not letting any coolant from the overflow tank back into the radiator.

19 out of 19 people think this is helpful.

Sounds like your radiator cap won't release the vacuum. Good practice to replace every time you flush the coolant.

9 out of 9 people think this is helpful.

I'd check for blockage at the radiator with a lazer spot thermal gun~

3 out of 3 people think this is helpful.

I would lean towards rad cap also but if the system has a bleeder valve in it you need to bleed system to rid it of air-

4 out of 4 people think this is helpful.

Judge_roy: there original poster stated no overheating. Blockage in hose would lead to overheating. ahjorge: while air in the system is no good and needs to be bleed out, it doesn't explain why a vacuum develops. The only device which controls vacuum within a cooling system is the radiator cap. If the cap is functioning, then the hose to the reservoir is blocked not letting coolant back into the system. A properly functioning cap will hold 15-16 psi of pressure, and hold little vacuum in order to refill a cooled down system. I've seen a few reservoir caps become clogged, but since its a dexcooled system (very common for gunk buildup in the cap region), the cap and res hose are the two suspects I normally look for.

15 out of 15 people think this is helpful.

Edit: blockage in system, not hose.

4 out of 4 people think this is helpful.

this is why I like "counterflow radiators" where the fluid goes in through the bottom hose and exits the top hose (like the Toyota Tercel)...you don't see this condition with these~ still I stand by my assessment...radiator is chokin', perhaps a flush would be in order as a radiator replacement on these is a bit of a brew-haha~

1 out of 1 people think this is helpful.

I agree with Lars Cats that the fluid expands and contracts...the indication would be the difference between "full hot" and "full cold" on your translucent coolant reservoir....how is that level anyways? able to put coolant out, but BLOCKED from bringing it in~?

3 out of 3 people think this is helpful.

The directional flow of the radiator has no impact on pressure or vacuum creation when the vehicle is turned off. I have seen plenty of imports, especially the 2.2 Camrys with the extremely long upper hose, collapse due to faulty caps or blockage within the reservoir hose.

4 out of 4 people think this is helpful.

Got a new cap today if that don't work I'm going to change the hose to the overflow/ puke bucket........I forgot the last Pontiac I had was a sunfire and I had to replace the cap on it several times........Have any you heard of flushing the radiator with Tide....we used to do it all the time on the old ones but I didn't know if you could do it to the newer vehicles??? 05 Bonneville?? Any thoughts?

4 out of 4 people think this is helpful.

BTW I had also put a new water pump on it this week and yes we did bleed it several times...


I flushed it with water this week but I still think there is gunk in there....may try to flush it again after the cap and overflow hose has been replaced......Do they sell the flushing agents at auto stores or do you have to take it to a garage?

1 out of 1 people think this is helpful.

Thanks everybody hope this gets fixed soon...Appreciate ALL the advice and sorry but this girl doesn't have a lazer spot thermal gun~ and she wouldn't know how to use it if she did have one...lol....btw glad I found this site.!

3 out of 3 people think this is helpful.

Well? Did you figure it out? That what these posts are for. to get suggestions, try them, post what worked. Not that hard to do, just post what actually fixed it like all the other posts. Simple.

1 out of 1 people think this is helpful.

Yes after asking 4 mechanics and 3 "shade tree" mechanics.....I bought a new radiator cap and the hose collapsing problem was fixed.....This has happened on both a sunfire and a bonneville.....This GIRL just used the process of elimination and figured it out herself...Simple enough?

3 out of 3 people think this is helpful.

Sooooo, my response to "replace radiator cap", in the second response, didn't fix your problem?????

3 out of 3 people think this is helpful.

I should say Lars and my answer.

1 out of 1 people think this is helpful.

Just wanted to let folks know this was very helpful and replacing the radiator cap solved the problem. Re-cap of my issue; Changed the oil, flushed and filled the radiator, changed out the fuel filter but would only get heat when I was in motion. Every time I would stop at a light it would start going cold. I thought thermostat at first but, I had no gage jumping, engine was not getting overly hot, no water in my oil, no leaks, no water loss. After reading stuff here I changed out the radiator cap but at first I was still having the same problem when just driving in residential area. However, after my hour commute over freeway it seemed to have worked out whatever air bubble I must of had as everything is working normal now. Thanks for the assist

2 out of 2 people think this is helpful.

You can get them at auto stores, make sure you follow the instructions carefully and keep an eye on your temperature gauge. You may want to check the thermostat after you've flushed it this way as freed up sludge can deposit itself on there and block it.

4 out of 4 people think this is helpful.
Best Answer

I'd never use any detergent in a cooling system as you have no idea whatever deposits it leaves in the system and how these react with the coolant. There are specifically formulated flushing agents for the cooling system you can use, although in my experience clean water is good enough for most radiators if you flush them every other year.

3 out of 3 people think this is helpful.

Mitsubishi Pajero 3.5 V6 with 6g72 engine. This is all great info, it has been very helpful, but, I've still got a collapsing top radiator hose after rad flush, new cap and bleeding. Could this be a cylinder head problem?

1 out of 1 people think this is helpful.

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