what happens when car runs without radiator cap on

Asked by May 05, 2013 at 09:06 PM about the 1996 Chevrolet Lumina 4 Dr STD Sedan

Question type: General

car was run with out radiator cap on want to know what damage was done car is over heating after ten minuets of driving

10 Answers


The damage could be anywhere from minimal to head warpage. I'd recommend getting your car inspected for damage by a licensed mechanic. Best wishes! -Jackie

1 people found this helpful.

An automobile engine needs a cooling system to remove heat. For the system to work correctly, it must be self contained--sealed because it uses pressure to function properly. The pressure keeps the coolant from reaching a boiling point as quickly. As the temperature increases the coolant becomes steam. Without a radiator cap, the liquid overflows. Engine overheating can have devastating consequences. The engine begins to "ping" and lose power. This can cause piston, ring and rod bearing damage. Pre-ignition can occur, which creates weak places or "hot spots" which could burn holes in the pistons. Blown head gaskets can occur, cams can freeze up and break. Hoses and radiators can burst.

17 people found this helpful.

I agree with all the above. Cap must be good and proper pressure to work properly. Does it over heat while normal driving or does it mainly happen when you come to a stop and idling? If it happens after you stop check to see that your fan is running. It should come on at idle if temp is getting to high.

3 people found this helpful.

First thing is to now change your thermostat... I had a Chev Wagon 1989 and it needed that... If your car is older then the rad may be now pooched. if you look at the rad and run your fingers across the bottom rad weaves they may be no longer connected. Replace with a 2 core Rad. Also consider a transmission oil cooler... Makes a better running car and your tranny and alternator will last longer. If you have an older than 86 forget the car, Head gaskets blow when overheated.

1 people found this helpful.

"what happens when car runs without radiator cap on" - it depends on how long it was off and what happened. When the cap is off, the coolant boils at a lower temperature. --- Full the reservoir, put the cap on and see what happens.

8 people found this helpful.

You Wrote: ......." car is over heating after ten minuets of driving "....... I'm assuming, that after refilling the cooling system, and replacing the radiator cap, the car overheats after 10 minutes. Question: After refilling the cooling system, Does the coolant Stay in the system, or is it leaking out of the block or radiator, somewhere other than the radiator or coolant recovery tank???.........if the Coolant is staying in the system, and the car seems to run fine, but overheats after 10 Minutes.....Replace Your Thermostat....... it's very possible it's Stuck Closed........ it's True as previously stated..... all sorts of Evil can happen to your engine, after it has a serious Over-Heatage..... my sweetheart once drove down the highway for quite a while in my old '91 Pontiac Sunbird with a 3.1/V6, before noticing the red lights on the dash..... surprisingly, everything was fine..... I changed the Thermostat anyway.... it's Good Policay to do so, after an Over- Heatage...... after you change the thermostat, add a good quality cooling system sealer (in case you have a minor leak somewhere, like at a freeze plugh), and refill the system. Run the engine. Check for Leaks. On top of your Thermostat Housing, there may be a small fitting, it's an air bleed valve. If it's there, open the bleed valve, til no more air comes spitting out of it... keep an eye on the coolant level. In fact, if everything works out OK, keep an eye on the coolant level for days, since there might be more air in the system, even after bleeding. Also, keep an ear out, and inspect regularly for leaks, your water pump, especially underneath. They too often go bad when they are run dry after an overheatage. Good Luck! .......I hope everything is Cool! ......sorry, just had to add that....... jvb.......PS. if everything works out OK, change your oil, it too may have gotten cooked as well.

7 people found this helpful.

I had This problem Today I pore the coolent and forgot to fix the Radiator cap as a result My Radiator Runs Hot on every Signal Light and smoke Is coming out from the Radiator So I stopped My vehicle and Purchased Coolant and Radiator cap. Now it is working fine

3 people found this helpful.

I must be stupid. Besides the radiator cap there is a drain hose, open to the air. It is almost the same to work without cap.

3 people found this helpful.

I let my sister borrow my car vy commodore 03 model, i forgot to put the radiator cap on b4 she left, it over heated halfway to Forster from taree and now it won't start what's the worse outcome any comments available?

3 people found this helpful.

If it ran fine before, but now it won't start after overheating, you've most likely warped the cylinder head due to overheating and compression for startup can't be achieved. Head gasket repair and resurfacing the head is most likely the next step. Sorry.

Your Answer


Looking for a Used Lumina in your area?

CarGurus has 112 nationwide Lumina listings and the tools to find you a great deal.


Chevrolet Lumina Experts

  • #1
  • #2
    John Saffrahn
  • #3
View All

Related Models For Sale

Used Chevrolet Impala
395 Great Deals out of 25,679 listings starting at $999
Used Chevrolet Malibu
454 Great Deals out of 49,621 listings starting at $2,111
Used Chevrolet Monte Carlo
4 Great Deals out of 930 listings starting at $2,500
Used Toyota Camry
753 Great Deals out of 70,883 listings starting at $1,200
Used Chevrolet Tahoe
525 Great Deals out of 36,647 listings starting at $1,299
Used Chevrolet Caprice
125 listings starting at $9,499
Used GMC Sierra 1500
707 Great Deals out of 58,603 listings starting at $1,995
Used Chevrolet Cavalier
588 listings starting at $3,495
Used Ford Taurus
183 Great Deals out of 15,909 listings starting at $981
Used Ford F-150
2,304 Great Deals out of 216,125 listings starting at $1,300
Used Buick Century
580 listings starting at $1,000
Used Buick Regal
77 Great Deals out of 4,073 listings starting at $4,984
Used Nissan Altima
698 Great Deals out of 70,182 listings starting at $950
Used Ford Mustang
258 Great Deals out of 36,949 listings starting at $1,000

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.