the job of the radiator cap

 

I learned this only 2 years ago when I replaced my wife's water pump. You know how it goes, do the job, then super paranoid about any subsequent leaks, and checking very carefully for the next week or so.....

I noticed an oddity. The coolant level was high when the car was hot, and when the car was cold. In other words, I would expect the coolant to be at the full line cold, and even higher when hot.

What I observed was the coolant was in the overflow tank where I would expect it to be when hot. Overnight, it was still there. Huh?

The internet led me to believe I've got air in the system. So, I got me a $20 funnel (spill proof it has a stopper and adapters for different makes of cars), which is installed at the radiator's mouth in place of the cap, while car is running. When it gets hot and thermostat opens, it starts to fill the funnel, as opposed to running out and over the sides of the radiator. Now the engine can be run so that air bubbles come out. I did this procedure extensively and felt satisfied.

Next day, same thing! Huh? And by chance, I noticed the upper radiator hose was collapsed overnight, normal when engine hot.

Now, the internet led me (though not easy to find) to believe that indicates a faulty radiator cap. Got a new one (OE) and voila, all good.

Coolant high in the recovery tank when hot, back down when cooled overnight.

Flash forward 2 years, I notice the radiator hose is once again collapsed when cold. Replace the cap, and normal again.

I have to say this...as much as I am a GM fanboy, there are so many aspects of their products that are substandard I bet even in 2022 (well documented on YouTube). I bet you that 109k Escalade that I love shares so much in common with my wife's car in build quality. Who ever heard of a radiator cap that fails in 2 years when it is OE?

The kicker was the DRLs burning out, known issue, TSB from like 1995 to 2014! lol They knew about it that long and never corrected it until the technology went to LED.

Vibration?

johnnatash4 wrote:

The kicker was the DRLs burning out, known issue,

I wonder if the installation exposed the bulbs to excess vibration. Years ago I learned that a certain business jet got only a few hours lifetime from a standard bulb for a certain navigation light position because the combination of airframe and mounting characteristics shook the bulb way more than usual.

--
personal GPS user since 1992

I have a 2006 GMC Canyon

As much as I like this truck, it does have its issues. 1. I had to have the engine replaced at 48,000 miles because of the sleeve liners in the cylinders. GM covered the cost of that but you would think that their engineers would know that the expansion rates of steel and aluminum are different. 2. Third brake light issues. As the truck gets older, the light gasket will start leaking. A bead of silicone or RTV will stop the leaking. 3. The thermostat is located behind the left front wheel well, which necessitates removing the front tire and the wheel liner to get to the thermostat. 4. The brake light covers leak causing moisture to get into the light housing. Again, silicone or RTV would take care of that issue. 5. Rust forming on the passenger side of the truck above the rear wheel requiring the side panel to be replaced. The body shop owner told me that it almost always occurs on the right side of the vehicle. He said that it very rarely happens on the drivers side of the vehicle. A lot of simple stuff that if taken care of in the manufacturing process would result in a better product.

--
It is impossible to rightly govern a nation without God and the Bible. ----George Washington

air in the cooling system

Any time you see indications of "air" in the cooling system and it can be fixed by replacing the pressure cap, that is good. If it happens again and again, suspect a leak from a cylinder into the cooling system. A chemical test for the coolant is available that shows products of combustion. A leaking head gasket could be causing it.

Certain cars are prone to head gasket leaks. Sometimes, an exhaust manifold can leak into the coolant.

Radiator caps

Unless I missed it there was no mention of whether the replacement cap was original equipment or after market. Although I haven't had to replace many caps, I have had good luck with Stant caps.

More on rad caps

My old diesel blew a head gasket and as mentioned it blew some air into the coolant. At least on the diesel, probably not on a gas engine, the black soot was seen floating on top of the coolant. WHEN COLD you can try opening the radiator cap with a rag over it and start the engine leaving the cap open. You will probably see signs of the exhaust bubbling through the coolant. Depending on the vehicle that quick test might not be possible if you can't look into the radiator.

what I read

maddog67 wrote:

As much as I like this truck, it does have its issues. 1. I had to have the engine replaced at 48,000 miles because of the sleeve liners in the cylinders. GM covered the cost of that but you would think that their engineers would know that the expansion rates of steel and aluminum are different. 2. Third brake light issues. As the truck gets older, the light gasket will start leaking. A bead of silicone or RTV will stop the leaking. 3. The thermostat is located behind the left front wheel well, which necessitates removing the front tire and the wheel liner to get to the thermostat. 4. The brake light covers leak causing moisture to get into the light housing. Again, silicone or RTV would take care of that issue. 5. Rust forming on the passenger side of the truck above the rear wheel requiring the side panel to be replaced. The body shop owner told me that it almost always occurs on the right side of the vehicle. He said that it very rarely happens on the drivers side of the vehicle. A lot of simple stuff that if taken care of in the manufacturing process would result in a better product.

Was that the GM DRL circuit had dirty voltage, with the volts hitting 16V at times. This burned out bulbs frequently. Imagine if you could get $10 for every GM vehicle you spotted that had a burned out DRL? You wouldn't have to work, just drive around. Think about this...you don't activate DRLs by simply turning the ignition on...the engine must be running. I at least observe this on my American and Japanese car. German car, the DRLs do turn on with ignition, and engine off....

The official fix on the TSB was to instead of the 3157 bulb, use a 4114.

UM, the 4114 is rated for like 31.x watts, while the 3157 is 27.x The 3157 already turns sockets brown from heat. GM felt there was a chance that the 4114 could withstand the dirty voltage better before blowing. My point is it really covered the years 1995 to 2014, where they never corrected the issue. Tell that to a GMC Acadia owner who has HID headlamps. The heat from the DRL melts the housing and they have a $1,400 replacement!

I since went with 3157 LEDs, and I measured that they draw 3.7 watts and cost $2 each in a pack of 10. They do only last about 4-6 months which I take it is quality control. Sometimes a led rattles off. They look more normal nowadays.

To those who have suggested head gasket issues, I think that is not applicable in this case, and what I first came across. The blatant indicator is the collapsed upper radiator hose, which means the engine cannot draw coolant from the overflow, as it is cooling down. Basically, and I never thought of it, the radiator must pass through the radiator cap, in order to access the overflow tank. I'm pretty sure in classic cars, that's not the case, there is a tube maybe from the tank to the radiator, not really sure but I for some reason thought that.

Here's an example, this is not my cap but the Gates equivalent, I used OE:

https://www.amazon.com/gp/product/B000C2WF4K/ref=ox_sc_saved...

Hose was collapsing
Reviewed in the United States on February 10, 2021
Verified Purchase
Changed out the water pump and noticed the upper hose collapsing after it got cold. thought it was because it was low on coolant. Let it run without the cap to burp the system, found out the thermostat is stuck open too.... ANYWAYS. Changing out the radiator cap solved my collapsing hose issue and its now using the expansion tank like it should.

p.s. in the 90's I considered Gates to be top notch. Today, not sure. For belts I like Bando, even for GM.

I do a coolant drain/fill as

I do a coolant drain/fill as part of my 4 year maintenance plan (regardless of mileage) for any vehicle owned. Part of that involves replacing the rad cap. Why? Mechanic friend suggests that to keep headaches to a minimum. OP's post is a good example why. Granted these aren't american cars - Japanese and Korean (infiniti, honda, kia), but the practice still holds.

For cooling refill I use a vacuum filler. This was actually quite needed on the nissan because of the goofy cooling system design and difficulty in getting all the air out. With vacuum fill there's no need to burp/run the engine after to ensure all air is removed.

Gates and Stant are part of Tomkins

johnnatash4 wrote:

p.s. in the 90's I considered Gates to be top notch. Today, not sure. For belts I like Bando, even for GM.

Gates today is part of Tomkins PLC, a London based firm with essentially two sub groups; Industrial & Automotive and Building Products. The Industrial and Automotive Group includes both Gates and Stant, also Trico and a few other product names not likely to be heard of in this country.

--
John from PA

what

zx1100e1 wrote:

I do a coolant drain/fill as part of my 4 year maintenance plan (regardless of mileage) for any vehicle owned. Part of that involves replacing the rad cap. Why? Mechanic friend suggests that to keep headaches to a minimum. OP's post is a good example why. Granted these aren't american cars - Japanese and Korean (infiniti, honda, kia), but the practice still holds.

For cooling refill I use a vacuum filler. This was actually quite needed on the nissan because of the goofy cooling system design and difficulty in getting all the air out. With vacuum fill there's no need to burp/run the engine after to ensure all air is removed.

What is crazy is that Toyota pink SLLC has a 10/120 drain interval from the factory. 10 years? From then on, 5 years (never understood how the interval could be cut like that).

So when I bought my Lexus used in 2016, it's a 2006, I got it home and there was zero coolant in the overflow, and zero coolant to be seen in the radiator!

It never overheated but I thought ruh roh I've been ripped off, blown head gaskets!

Come to find this was common with people buying this LS model used. Since the interval was 10 years, nobody including all the dealer servicing ever checked it. Not only that, the viewing window is backwards and the air scoop thing needs to be removed to even access the overflow.

Coolant and brake fluid are often overlooked. I once came across a woman berating a Firestone worker for recommending brake fluid. I then interjected that I do brake fluid every 2, although I hear Honda recommends 3, but it is a needed service at some point since brake fluid is hygroscopic. She calmed down and the service guy thanked me. Just hated to see that and maybe help out.

The biggest problem with coolant and brake fluid is properly recycling them--I have to wait for an event, unlike motor oil which I can bring to the auto parts chain....

p.s. my wife's reservoir has been going up and down with the engine temp ever since I replaced the cap, and no more collapsed hose. What is a PITA is there are the plastic push pins that are now all aftermarket, and they all break when I take the cover off to access the radiator cap (slightly too tight I guess). I have to retrieve pieces when doing this job...

Sounds to me that the

Sounds to me that the replacing of the radiator cap the second time wasn't the fix, but removing the cap was. The old cap may still be good. A collapsed hose (assuming the hose is good) indicates there is a vacuum in the system which should never be and is not related to the cap unless it is the wrong one. Make sure your hose to the overflow bottle is not clogged or getting clogged by junk getting sucked in from the overflow bottle.

interesting

sunsetrunner wrote:

Sounds to me that the replacing of the radiator cap the second time wasn't the fix, but removing the cap was. The old cap may still be good. A collapsed hose (assuming the hose is good) indicates there is a vacuum in the system which should never be and is not related to the cap unless it is the wrong one. Make sure your hose to the overflow bottle is not clogged or getting clogged by junk getting sucked in from the overflow bottle.

In the old days, they tested caps, right?

It works now perfectly, as I've been checking it regularly when the engine cools. Also odd other GMs noticed the same thing. Could very well be debris. Thanks.

@johnnatash4 I think it's

@johnnatash4

I think it's fair to say when doing a drain/fill you're not getting 100% of the fluid out. Probably varies how much with the car/engine. Thus the 5 yr interval there after. Frankly I'd stick with a 4-5 yr interval to begin with, more so with higher mileage.

Coolant for the infiniti wasn't cheap at ~$20/gal oem premix. I chose this over aftermarket as it's only changed every few years. I also had an extended warranty on the car from infiniti, so if there was a claim, they couldn't say I used the wrong fluid. Also, just how much cheaper is aftermarket these days. Long gone is the $4/5 /gal peak coolant prices (full strength too, not premix).