Resevour cap & Idle

Radiator cap on my truck is 20 years old. Came from the factory. My air cooled VWs never had a radiator cap replaced. My three water cooled VWs had original caps but they only had/have 170,000 miles to

300,000 miles. I was not aware that a radiator cap was a wear item on any car but I have only had a few cars over 30 years of driving.

There is a screw on the side of the throttle valve on the old style mechanical fuel injected VWs and Volvos. Not the screw by the linkage but one on the side of the throttle valve. That screw has an oring on it. I had to Loctite mine with some low strength (blue) Loctite because it kept backing out even with a new oring.

I never had to buy one for my Mk2 GTI in over 200K miles.

Can youconfirm what engine and where you are? (US, Canada, Europe, etc.,

1.8, 1.6, etc.).

If it's a US/Canada 1.8L, the high idle can be caused by several things...O2 sensor bad (not real cheap), coolant temperature sensor bad (cheap), or timing off (free but you have to know how to adjust it and have tools to do so).

Many times a fast idle results from a vacuum leak .

Thanx to everyone who replied! I appreciate the info and will check out my car further.

Thanx Ken

.

. My

Air cooled vehicles have a radiator?

Hence no cap replacement! :)

Hmmm technically aren't most vehicles "air-cooled" with the coolant as a medium (cooled by air) to allow the transfer of heat out of the engine? Or was this some joke! ;-)

One of my high school buddies would winterize his Corvairs. That would be winter windshield wiper fluid.

Well if you owned Duetz tractor or a Franklin car you might also be familiar with the phrase air cooled but you know that. You are just pulling legs. ;-)

Dave AKA,

You always have great advice and knowledge, but I think you're splitting hairs on this one! I guess based on that line of logic, you could argue that an air-cooled 911 that drives through a puddle on a hot day is technically water-cooled. Or am I splitting the same hair?

lol Yep same hair!

Only if the cooling air is misted with puddle or rain water. Actually if one was splitting hairs I think every engine that has a crankcase with oil in it is oil cooled. Some engines even have special holes in the connecting rods to squirt cooling oil on pistons.

lol Yep same hair!

My 88 Fox has the original cap on the coolant reservoir. It simply screws on. Not vented. Just a hard plastic cap.

I might be wrong, but I believe the large area in the reservoir between cool and hot lines, then to the top of the reservoir acts as an expansion area.

For the jokers, their is a such thing as primary and secondary coolant systems.

Addressing another comment: Radiator caps with psi rating do need intermittent replacement. They do wear out.

Hmmm Could you post a picture of the inside of that cap? That will be a new one on me and I am curious! All that I have seen usually have a release valve on the inside of the cap, and some of those valves are not seated properly.

thanks!

AH HAAA So most engines can be liquid AND air cooled! You are a wise one Jim Behning! ;-)

Geez now I see someone saying that the metal and the paint also cool. lol

WHY WHY WHY did I split the first hair! >

The pressure caps I have seen all have pressure ratings and a mechanism to relieve pressure. Look inside. Somewhere there is a cap that is set to maintain a certain pressure. Excessive pressure causes hoses and reserve tanks to blow up. There is a pop off thing on a cap on your car.

So when do the caps wear out? I have cars over 20 years old with no coolant issues. I have cars with over 300,000 miles with no coolant issues. What would cause them to wear out? How would you know? The VW Bentley service manual show radiator caps being tested for pop off pressure. I think it is a go/no go system.

Give me a couple of days. The coil went out at the local dollar store parking lot. Replaced coil in the parking lot, runs fine. Arranging transportation back to the store so I can drive it back home.