Bad radiator cap?

toyotanos

What will we break today?
Staff member
Super Moderator
Nov 29, 2008
2,841
2
38
Coon Rapids, MN
Over pressurization of the cooling system,
lack of presure in cooling system,
Sustained improper pressure in cooling system,
Collapsing radiator hoses,
exploding radiator hoses,
Vacuum in cooling system,
Overflow level never changes,
cap is leaking coolant out,
cap is missing parts of itself,
etc.

What are you dealing with that leads you to think the cap is bad?



cliffs: a lot of things can happen, it just depends on how it fails :p
 

enjoi.this

Formerly ChrisC
Aug 18, 2008
674
0
16
Kelowna, BC
Pushes coolant into the overflow bottle as it warms up. Eventually pushes enough to spit on the ground usually before it even gets to temperature.
 

bioskyline

New Member
Oct 21, 2010
1,236
0
0
powell river bc
pull the cap off and check the rubber gaskets on it. sounds like its not sealing properly. also a new rad cap is 5 bucks? if it looks bad, try a new one.
 

suprafanatic

New Member
May 25, 2007
1,607
0
0
36
Greenwood, IN
enjoi.this;1824394 said:
Pushes coolant into the overflow bottle as it warms up. Eventually pushes enough to spit on the ground usually before it even gets to temperature.

This is pretty much what I'm experiencing. I have two different radiator caps, BOTH are pretty old caps. The one I originally had on I drove for about 2 hours and a decent amount of the coolant had been pushed out into the overflow tank and started to drip out onto the ground. Once the car cooled I took the cap off and couldn't see any water in the radiator so I had to add some. Second cap I had I put on to see if it would make a difference on the two hour drive back home. With the second cap it did let some coolant out but not nearly as much. I took the cap off again after cooling and I could still see water near the top of the radiator only like 1/4 inch down. Should I get a new cap?

I went to autozone to get a new cap but the one they had for my car didn't fit my radiator at all, it was to small.
 

suprafanatic

New Member
May 25, 2007
1,607
0
0
36
Greenwood, IN
ATL88Supra;1824405 said:
all of the above + BHG

This is exactly why I didn't post my symptoms in the very first post. I've been around long enough to know how that will end up. I have good reason to believe its the cap, but can't find a new one that fits.
 

emiliorescigno

Supramania Contributor
Sep 17, 2006
1,199
0
0
Woodbury, MN
suprafanatic;1824411 said:
This is exactly why I didn't post my symptoms in the very first post. I've been around long enough to know how that will end up. I have good reason to believe its the cap, but can't find a new one that fits.

If you're having trouble finding a decent cap, do yourself a favor and go to your local Toyota dealership. The extra $10 is completely worth it.
 

toyotanos

What will we break today?
Staff member
Super Moderator
Nov 29, 2008
2,841
2
38
Coon Rapids, MN
Go to the dealer- should be around $15 and it'll fit for sure (unless you're running an aftermarket radiator) But even then I'm using an OEM on my Koyo.
 

suprafanatic

New Member
May 25, 2007
1,607
0
0
36
Greenwood, IN
would they have them in stock or would they have to order them? I've gotten one from autozone in years past that fit my 87. Maybe the guy that gave it to me this time was a dummy lol. They aren't to bright around our autozone.

But other than it pushing out a little coolant the car has NO other issues. It doesn't over heat unless I drive with the really bad cap on for a long period of time. Second cap it wont over heat cause it doesn't let enough out. No oil in the coolant, no coolant in the oil. No milkshake under the oil cap. No loss of power. Starts up right away and drives great. No smoking what-so-ever even under boost, had a friend follow me for a while to check.
 

emiliorescigno

Supramania Contributor
Sep 17, 2006
1,199
0
0
Woodbury, MN
The best person to ask if they have a cap on hand is the person who works the parts counter. Give them a call tomorrow morning and you'll know. I would be willing to bet they do have one on hand, since it's universal for many different Toyota vehicles.
 

GrimJack

Administrator
Dec 31, 1969
12,377
3
38
56
Richmond, BC, Canada
idriders.com
For the low fluid in the radiator, check the hose from the radiator to the overflow, and the hose to the bottom of the overflow. If those have a leak, it will push coolant out just fine, but suck in air when it cools.
 

suprafanatic

New Member
May 25, 2007
1,607
0
0
36
Greenwood, IN
So when you say check those two hose's for a leak are you talking an air leak? or a coolant leak from the hose? I know the hose going down into the overflow tank is extremely loose, it falls off almost every time I pull the cap for the overflow. So maybe its pulling only air back instead of coolant.. but still why would it be pushing out to much coolant?
 

suprafanatic

New Member
May 25, 2007
1,607
0
0
36
Greenwood, IN
Actually it just clicked with me, I think your onto something with my issue. The first radiator cap I had on was bad and it was allowing to much coolant out, period. The second cap I used barely let any out, but when it cooled it couldn't suck anything but air back in and that's why it was like 1/4 inch low in the radiator. I'll make sure the hose going into the overflow tank is tighter and check for any other air leaks. Thank you for bring that point up, not sure why I didn't think of that, but I didn't lol.
 

Nick M

Black Rifles Matter
Sep 9, 2005
8,871
37
48
U.S.
www.ebay.com
suprafanatic;1824391 said:
So what exactly would be the symptoms of a bad radiator cap?

It will only fail one way, which is losing the seal and resulting pressure. That would push the coolant into the overflow more than normal, and it wouldn't pull back in when cooling.
 

gtsfirefighter

SM Expert on White trash
Sep 26, 2006
2,965
0
36
54
Weatherford, Texas, United States
I bought a new Toyota cap from the dealership for $17.00 last week. The had to order it but I got it the next day.

On the other hand, my old 91 turbo had the same symptoms you're having. I thought it was the cap. It wasn't...
Do a leakdown test. That's how I discovered it wasn't the cap. If you're car smokes and sputters after a leakdown test...well...
 

GrimJack

Administrator
Dec 31, 1969
12,377
3
38
56
Richmond, BC, Canada
idriders.com
suprafanatic;1824475 said:
Actually it just clicked with me, I think your onto something with my issue. The first radiator cap I had on was bad and it was allowing to much coolant out, period. The second cap I used barely let any out, but when it cooled it couldn't suck anything but air back in and that's why it was like 1/4 inch low in the radiator. I'll make sure the hose going into the overflow tank is tighter and check for any other air leaks. Thank you for bring that point up, not sure why I didn't think of that, but I didn't lol.
It's actually a very common thing to overlook - they aren't pressure hoses, so nobody thinks about them leaking coolant, never mind air.