Correct XR4Ti Radiator Cap Part Number

[anglin]

All,

I replaced the radiator cap on my road car (1987.5 XR4Ti) recently as a part of some cooling system preventative maintenance. I purchased a Stant unit from Autozone with the pressure release lever. The one they sold to me on my first trip was Stant PN 7916 which immediately struck me as being too small. It's octagonal in shape (more like a square with chamfers at the corners). As soon as I arrived home and popped the hood, I confirmed that it was the wrong unit. I took the old radiator cap with me and they matched it to one on the shelf.

The correct PN is 7816.

The Autozone web page has the incorrect PN. Here's the incorrect info:

[Stargazer7467]

I have a 7016 on mine with no problems from the cap anyways.

[Ed Lijewski]

Why would you roll with a cap with the pressure release lever?

YMMV

[anglin]

Why would you roll with a cap with the pressure release lever?

Habit, I suppose, since about nahnty-fo'. Is there a problem with them?

[Rocky's Wrench]

Why would you roll with a cap with the pressure release lever?

Habit, I suppose, since about nahnty-fo'. Is there a problem with them?

Besides the fact they're crap, nope, no problem...

[John Brennan]

That's why I run with Scottish rad caps.

I had one of the lever types for a couple years on my last car-- no problems with the cap; it was the jug that finally succumbed to living in too-close propinquity with the turbo. Plastic can only take so much... ''ya know?

All cap issues went away, however, when I got a replacement jug with the newer-style screw-on cap-- definitely a step in the right direction, until that jug crapped... I mean cracked. The ultimate solution proved to be moving to the 89-style jug, which looked as new as when I got it when I finally sold the car years later.

Of course, my new baby is an '89, so the good cap with the good location for the jug are givens.

[anglin]

Besides the fact they're crap, nope, no problem...

Whether your statement is accurate or not, it doesn't expand on the problem, if there is one. The one I replaced had been in use since 1994 or 1995. It didn't display any malfunction until recently. I popped up the lever, which was rusty and balked at my efforts, to remove the cap and reinstalled it. Two days later, I later discovered that the coolant tank was bubbling when my wife complained of a sweet smell when she drove the car. I'm pretty sure the pressure release mechanism finally corroded to the point of not functioning properly and the radiator cap didn't work any more.

I assume Ed was just getting at the fact that there's no point to the extra mechanism and associated cost and possibility for failure. But I'm just guessing.

I know this is a whole 'nother issue, but I like the screw on cap that Brennan likes. Yeah, there's no overflow control... *sound of a can of worms opening again*

[John Brennan]

"I'd sooner have no tail, and no flies."

Benjamin the Donkey, Animal Farm

[Ed Lijewski]

Ed was getting at that his experience is the same as, apparently, Rocky's Wrench: the lever caps have a higher failure rate, appear to be less reliable as well. And just what purpose does having that lever serve--for true and informed gearheds, is a metaphysical question that begs to be answered. Obviously raising the lever releases pressure, but almost certainly as well some vapor if not coolant, too. So there's a potential mess, right there. If lifting the lever was done to add coolant, how is that much better than using a wet towel to unscrew either the OEM metal cap or even the non-metal later model screw on one? Lever caps are just so old-school technology...that if anything, I should be running with one, not Anglin. And I forswore lever caps years ago.

YMMV

[Ed Lijewski]

That's why I run with Scottish rad caps.

I had one of the lever types for a couple years on my last car-- no problems with the cap; it was the jug that finally succumbed to living in too-close propinquity with the turbo. Plastic can only take so much... ''ya know?

All cap issues went away, however, when I got a replacement jug with the newer-style screw-on cap-- definitely a step in the right direction, until that jug crapped... I mean cracked. The ultimate solution proved to be moving to the 89-style jug, which looked as new as when I got it when I finally sold the car years later.

Of course, my new baby is an '89, so the good cap with the good location for the jug are givens.

I've got a new '89 coolant reservoir FS (make serious offer if interested):

http://i60.photobucket.com/albums/h28/P ... 010036.jpg

YMMV

[John Brennan]

I was gonna mention that is also has the newer, improved, upgraded 3- belt crank pulley as well, but... nah...

[Ed Lijewski]

Thank you for reminding me to update everyone on how perfectly my two-crank pulley V-belt a/c connections continue to work! No squeaks, sqawks, slips or misses (or misters)! A wonderful design, for those capable of appreciating it.

You know where you can shove your three-groover...

YMMV

[anglin]

Ed was getting at that his experience is the same as, apparently, Rocky's Wrench: the lever caps have a higher failure rate, appear to be less reliable as well. And just what purpose does having that lever serve--for true and informed gearheds, is a metaphysical question that begs to be answered. Obviously raising the lever releases pressure, but almost certainly as well some vapor if not coolant, too. So there's a potential mess, right there.

Okay, perfectly sensible. When this radiator cap fails, I'll replace it with a normal, leverless cap. Given the number of miles and general condition, I suspect the Merkur will fail first.

Here's my feeling about the purpose and use of the lever. If you are removing a radiator cap and the coolant wants to flash to steam when the radiator cap is opened,

- a lever is going to be very easy to snap back closed and the steam is venting out the coolant dump tube.
- a cap without the lever is going to be partially/close-to-fully removed and the steam will be venting out the edges of the cap near the palm of your hand.

If coolant does start to overflow (which is caused by superheated coolant flashing to steam inside the engine when the pressure is released at the radiator cap) Closing the lever allows you to immediately shut off the flow.

Of course, all of this can be avoided by just letting the engine cool off enough. The point is essentially moot. The caps with levers are little more expensive and may have to be replaced a little more frequently, but unless they are bad right out of the box, the cost could be considered insignificant.

Meh. Not to say your points are invalid, but it just doesn't seem like that big of a deal.

I was gonna mention that ... but... nah...

[KhanTyranitar]

I used to use the lever style caps, I can vouch for the fact they are crap. They worked ok when new, but after a short while they would leak around the part where the lever goes in, and they would not hold proper pressure. For something like a radiator cap, it is an overly complicated design. The theory is that you can just relive the pressure without getting burnt. The reality is you are never going to release all of the pressure till it cools off. So if you's released the pressure if you try to take it off, it will spray hot coolant everywhere.

About the only time you ever need to do this is if the cooling systems isn't working correctly, and you need to release the pressure to get started on fixing it. There is an old saying, "An ounce of prevention is worth a pound of cure". This holds true for this situation, most cooling system problems can be avoided before they happen. So basically maintenance makes the need for a cap with a lever obsolete. I quit using them, and have not regretted the switch back. I find myself needing a pressure relief less when I don't have one. In fact I have never had a cooling system failure since I got rid of the cap.