Coolant Reservoir Cap Stuck

[SoCalDMC12]

Howdy all,

Yesterday, I tried to check my coolant level, but couldn't get the reservoir cap open... wouldn't even budge. Any ideas on how to unstick it?

[Bitsyncmaster]

Howdy all,

Yesterday, I tried to check my coolant level, but couldn't get the reservoir cap open... wouldn't even budge. Any ideas on how to unstick it?

You may need to push down as you turn it CCW.

[DMCMW Dave]

Howdy all,

Yesterday, I tried to check my coolant level, but couldn't get the reservoir cap open... wouldn't even budge. Any ideas on how to unstick it?

Big pliers


Sent from phone

[ALEXAKOS]

Big pliers
Sent from phone

You are truly an amazing asset to this forum!
In for the rescue, from work, home.. Now even from your phone.. During your lunch break?
A pleasure to have your expertise Dave! :)


Somebody make this fella MoM!

[SoCalDMC12]

Tried pushing down... no go. Will try a big rubber band next, then go to pliers. Fortunately, nothing seems to be wrong (knock on wood)... just wanna check the level.

[Rich]

Pushing down only helps after you loosen it about 1/4 turn. When the cap is closed it cannot move downward.

Since it's not turning at all you either need more torque or less resistance. The cap's two retaining ears are probably corroded/stuck to the under-rim of the filler neck flange.

Less resistance might come from a few squirts of your favorite spray penetrant, up under the 2 folded-under ears that wrap under the neck flange.

More torque can come from a better/larger grip (a thick, wet terry towel folded over the cap can be your next step) or better yet, a pair of these, along Dave's line:
https://www.channellock.com/Themes/Channellock/Images/product/category/420-straight-jaw.png

And consider getting a new cap before going any further. If it has been on long enough to be so badly stuck you'll likely find it's not much of a cap after you take it off - the seals are probably bad or soon will be, even assuming you don't bend it up with the pliers. If the cap or the filler neck get messed up don't drive it til you fix them.

[David T]

Pushing down only helps after you loosen it about 1/4 turn. When the cap is closed it cannot move downward.

Since it's not turning at all you either need more torque or less resistance. The cap's two retaining ears are probably corroded/stuck to the under-rim of the filler neck flange.

Less resistance might come from a few squirts of your favorite spray penetrant, up under the 2 folded-under ears that wrap under the neck flange.

More torque can come from a better/larger grip (a thick, wet terry towel folded over the cap can be your next step) or better yet, a pair of these, along Dave's line:
https://www.channellock.com/Themes/Channellock/Images/product/category/420-straight-jaw.png

And consider getting a new cap before going any further. If it has been on long enough to be so badly stuck you'll likely find it's not much of a cap after you take it off - the seals are probably bad or soon will be, even assuming you don't bend it up with the pliers. If the cap or the filler neck get messed up don't drive it til you fix them.

Don't know what cap you have on there but there are some caps (non-original) that have a lever on top. You have to lift the lever before it can turn. Made that way so you have to relieve the pressure before you try to remove the cap. If it is that stuck on there figure on replacing it.

[SoCalDMC12]

Don't know what cap you have on there but there are some caps (non-original) that have a lever on top. You have to lift the lever before it can turn. Made that way so you have to relieve the pressure before you try to remove the cap. If it is that stuck on there figure on replacing it.

No lever on the top. I've been able to open in the past by pushing down and turning CCW. I think I'm gonna leave it for now. I have a rally tomorrow and don't want to risk messing up the cap or filler neck. My car isn't showing any symptoms of overheating anyway... I just wanted to check the coolant level. I guess this will be a project for Monday.

Thanks!

[SoCalDMC12]

Less resistance might come from a few squirts of your favorite spray penetrant, up under the 2 folded-under ears that wrap under the neck flange.

Is the corrosion similar to hard water mineral build up? If so, I wonder is something like vinegar or some other acidic liquid could be used to break up the corrosion.

[DMC5180]

What type of header bottle do you have? OE plastic, stainless or aluminum. I recently put a new cap on my OE header bottle. It went on okay but when I tried removing the cap it got hung up on the filler neck step. The issue was with the two tabs on the cap. There were flat. The lacked the edge flair lead that aids in allowing the cap to rotate CCW while you push down. Once I was able to get the cap off I tweaked the tabs with a pliers to match the shape of the old cap. No more hang ups.

[Ryan King]

Tried pushing down... no go. Will try a big rubber band next, then go to pliers. Fortunately, nothing seems to be wrong (knock on wood)... just wanna check the level.

Maybe try clamping off the hose and removing the bottle...might need to get it on the bench. Be careful too, you dont want to apply too much pressure and rip the studs out of the pontoon.

[SS Spoiler]

Iv'e heard that on some replacement reservoirs the tabs were too long making radiator cap removal difficult.
some careful filing helped.

[Ron]

$.02

Take some side-cutters (dikes) to it and replace it with an AC-RC15 cap before you wind up with bigger troubles...

[SoCalDMC12]

Howdy, just an update:

Drove my D in an awesome classic car rally on Saturday... about 200 miles of mountain/canyon/coastal roads, and she performed admirably, with absolutely no signs of overheating.

Today I sprayed the lip under the reservoir cap with some WD40, waited a bit, and unsuccessfully tried to turn it by hand. I was later able to dislodge it with a wrench (very little force was necessary). I found some build up on the inside of the cap, and the filler neck which I cleaned off. The rubber gaskets on the cap were still in tact, and surprisingly pliable.

I added a bit of coolant, screwed the cap on, tested it (it turns fine now), and then ran the car for about 20 minutes. All is well! (Though I'll probably get a new cap sometime soon... seems like a good insurance policy.)

Thanks again!
31624

[skill]

Howdy, just an update:

Drove my D in an awesome classic car rally on Saturday... about 200 miles of mountain/canyon/coastal roads, and she performed admirably, with absolutely no signs of overheating.

Today I sprayed the lip under the reservoir cap with some WD40, waited a bit, and unsuccessfully tried to turn it by hand. I was later able to dislodge it with a wrench (very little force was necessary). I found some build up on the inside of the cap, and the filler neck which I cleaned off. The rubber gaskets on the cap were still in tact, and surprisingly pliable.

I added a bit of coolant, screwed the cap on, tested it (it turns fine now), and then ran the car for about 20 minutes. All is well! (Though I'll probably get a new cap sometime soon... seems like a good insurance policy.)

Thanks again!
http://dmctalk.org/attachment.php?attachmentid=31624&stc=1
Sorry to hear about your experience. Glad to see you pulled it off! :) That's some build-up... if I had this issue and probably will down the road do a complete systems flush jus' for peace of mind sake. :-)

[skill]

Howdy, just an update:

Drove my D in an awesome classic car rally on Saturday... about 200 miles of mountain/canyon/coastal roads, and she performed admirably, with absolutely no signs of overheating.

Today I sprayed the lip under the reservoir cap with some WD40, waited a bit, and unsuccessfully tried to turn it by hand. I was later able to dislodge it with a wrench (very little force was necessary). I found some build up on the inside of the cap, and the filler neck which I cleaned off. The rubber gaskets on the cap were still in tact, and surprisingly pliable.

I added a bit of coolant, screwed the cap on, tested it (it turns fine now), and then ran the car for about 20 minutes. All is well! (Though I'll probably get a new cap sometime soon... seems like a good insurance policy.)

Thanks again!
http://dmctalk.org/attachment.php?attachmentid=31624&stc=1
Sorry to hear about your experience. Glad to see you pulled it off! :) That's some build-up... if I had this issue and probably will down the road do a complete coolant-system flush jus' for peace of mind sake. :-)

[DMCMW Dave]

Yeah - time for a cooling system flush.

[Rich]

.....I was later able to dislodge it with a wrench (very little force was necessary). I found some build up on the inside of the cap, and the filler neck which I cleaned off.
(Though I'll probably get a new cap sometime soon... seems like a good insurance policy.)

Thanks for telling us the happy ending.

And for including a photo.

About that buildup. Check the overflow hose (small one that runs to rear of car over the tank) and the nipple at the filler neck it attaches to. Overflow plumbing is probably plugged someplace and causing the buildup/residue that made your cap glue itself to the neck. Or you've got a serious corrosion issue there. That's abnormal to say the least.

[SoCalDMC12]

Thanks for telling us the happy ending.

And for including a photo.

About that buildup. Check the overflow hose (small one that runs to rear of car over the tank) and the nipple at the filler neck it attaches to. Overflow plumbing is probably plugged someplace and causing the buildup/residue that made your cap glue itself to the neck. Or you've got a serious corrosion issue there. That's abnormal to say the least.

Thanks, was kinda thinking the same thing... to me, the build up didn't look so much like corrosion as it did dry (and semi-dry) coolant. I was trying to figure out how coolant could get splashed up there, and a stoppage in the overflow hose could explain it.

Cooling system flush seems prudent as well.

[Ryan King]

Thanks, was kinda thinking the same thing... to me, the build up didn't look so much like corrosion as it did dry (and semi-dry) coolant. I was trying to figure out how coolant could get splashed up there, and a stoppage in the overflow hose could explain it.

Cooling system flush seems prudent as well.

Definitely time for a flush. I drove my car daily for 9 years and have never seen build up like that, and I flush it maybe ever year or so.

[SIMid]

I hope it hasn't blocked any coolant channels in the engine!

[SoCalDMC12]

About that buildup. Check the overflow hose (small one that runs to rear of car over the tank) and the nipple at the filler neck it attaches to. Overflow plumbing is probably plugged someplace and causing the buildup/residue that made your cap glue itself to the neck. Or you've got a serious corrosion issue there. That's abnormal to say the least.

Well, fortunately, it was the former... the nipple that connects the hose to the neck of the reservoir was loosely plugged with sediment. No wonder there was so much build up... if any coolant made it up to the cap, it was blocked in. But I guess that the build up was loose enough not to cause any back pressure. After I cleaned it out I was able to blow air through the hose with no problem. Next... a coolant flush for piece of mind!

[SoCalDMC12]

I hope it hasn't blocked any coolant channels in the engine!

Me, too! But I don't think it's blocked up... as I mentioned earlier, it has never exhibited any cooling problems at all. In fact, the fans always kick in at the second tick mark from the bottom on the temp gauge - like clockwork. And, this D seems to take longer to warm up that my other D did.

[SoCalDMC12]

Hi All. So I went to my local parts store today to get a new cap. But, of course, there was no way to look up a cross reference part. The sales guy had me go in the back and start looking through their inventory for a match (I had my cap with me).

I found what looked like a match. It seems to fit fine... I can screw it on and off, and it has the same pressure rating as my old one. Is there anything else that I should look for, or does this seem good to go? Any info would be appreciated. (The Stant cap is the old one.)

31675316763167731678

[Rich]

Hi All. So I went to my local parts store today to get a new cap. But, of course, there was no way to look up a cross reference part. The sales guy had me go in the back and start looking through their inventory for a match (I had my cap with me).

I found what looked like a match. It seems to fit fine... I can screw it on and off, and it has the same pressure rating as my old one. Is there anything else that I should look for, or does this seem good to go? Any info would be appreciated. (The Stant cap is the old one.)

31676

Well, that was a logical move to match to the old cap pressure - but the old cap pressure rating wasn't stock/spec.

D caps are 15PSI, not 16PSI.

And, not that it matters much, the pressure-relief lever on the cap isn't stock, either.

Recommend getting a stock-spec 15PSI cap on there in place of that 16PSI cap. Without or with lever.

[SoCalDMC12]

Well, that was a logical move to match to the old cap pressure - but the old cap pressure rating wasn't stock/spec.

D caps are 15PSI, not 16PSI.

And, not that it matters much, the pressure-relief lever on the cap isn't stock, either.

Recommend getting a stock-spec 15PSI cap on there in place of that 16PSI cap. Without or with lever.

I was aware that the stock spec cap was 15 psi, but this one was on the car when I got it (9 years ago) and I haven't had any issues until now.

I tested the new cap, and unfortunately, it doesn't seem to work well. I let the car idle in my garage, and it took the usual amount of time for the engine to warm up to the 2nd tick mark from the bottom on the temp gauge. Shortly thereafter, the fans kicked in. But instead of cooling down, the temp kept rising to the middle tick. At that point I turned it off.

Gonna wait a couple of hours, put the old cap back on and re-test (if it still works, I can use it while I look for a 15 psi cap.

Thanks!

[Bitsyncmaster]

I was aware that the stock spec cap was 15 psi, but this one was on the car when I got it (9 years ago) and I haven't had any issues until now.

I tested the new cap, and unfortunately, it doesn't seem to work well. I let the car idle in my garage, and it took the usual amount of time for the engine to warm up to the 2nd tick mark from the bottom on the temp gauge. Shortly thereafter, the fans kicked in. But instead of cooling down, the temp kept rising to the middle tick. At that point I turned it off.

Gonna wait a couple of hours, put the old cap back on and re-test (if it still works, I can use it while I look for a 15 psi cap.

Thanks!

Bleed the air at the thermostat. Cap would not make the temp gauge go up like that.

[SoCalDMC12]

Bleed the air at the thermostat. Cap would not make the temp gauge go up like that.

Well, I put the old cap back on, and ran the car again. Heated up to about the second tick mark, fans kicked in, and this time it cooled down to a bit under that tick mark before the fans turned off (see photo). This is my car's usual behavior. For good measure, I cracked open the bleed valve, but no air came out.

I'll continue to look for a replacement cap, but at least I have my old one for the mean time.

Thanks to all. Please chime in if you have any insights.
31721

[DMC5180]

Very Interesting to see the photos of that heavy corrosion. Even more so that you have an ALUMINUM Header bottle. I don't think anyone has sold the Aluminum tanks in at least 15 years or more. I recall P J Grady used to sell them in the Mid 90's.

[SoCalDMC12]

Very Interesting to see the photos of that heavy corrosion. Even more so that you have an ALUMINUM Header bottle. I don't think anyone has sold the Aluminum tanks in at least 15 years or more. I recall P J Grady used to sell them in the Mid 90's.

I don't think it's corrosion as much as it is dried up coolant. The build up seemed almost crystallized.

I haven't seen another aluminum header bottle in the last 9 years...

[DMC5180]

I don't think it's corrosion as much as it is dried up coolant. The build up seemed almost crystallized.

I haven't seen another aluminum header bottle in the last 9 years...


Good point, I typically see crystalized coolant occurring when glycol is in the presence of oxygen. You typically see this at hose connections. A crystallized layer bids up between the hose and the barbed connection is seems most common when the barb is aluminum, But I've also seen it on plastic barbs too.

[skill]

If you experience this; Here's a solution to unsticking your coolant reservoir cap... I just used this tool on a Caddy parked for about 15 years and this cap was a frozen @#^%@! (Craftsman Auto adjustable Universal Oil Filter Wrench), Part #: 28-20523) today and it came off easily. Warning: It can be an aggressive tool so use carefully and don't over torque; http://dmctalk.org/attachment.php?attachmentid=31831&stc=1