chaddwick2005

A little intro, bought '00 XJ July 2011, but finally getting stuff done to it. So this last weekend, I did a complete cooling system overhaul (after reading about the 0331 heads, which I have, and not cracked yet, but no tupy, looked when replacing valve cover gasket), but after replacing water pump, tstat (180 w/drilled hole), hoses, radiator cap, putting zj 2737 fan clutch on, and flushing system, refilling with new coolant, bleeding air out, now jeep runs cooler, but the radiator cap leaks. It is a brand new 16 lbs cap from O'Reillys, part number 7616.

I did use the search function, and found where a guy had his hose from coolant overflow tank was clogged and that was why his cap was leaking, he cleared his out and leak went away. Checked my hose, clear, but cap still leaks.

Another member here "Bbasso" just did a coolant overhaul on his jeep (thread found here https://www.cherokeeforum.com/f2/i-b...41101/index10/ ) he went through 3 new 16 lbs caps before supposedly getting the right one, but after talking to him today, his is leaking again.

So my questions are,
-has anyone else had this problem where their caps leaking after cooling overhaul?
-has anyone used a higher pressure cap, say 18-19 lbs, and what was the outcome, did the cap hold pressure or what not.

Thanks,
-CZ

Fsher21

I would buy another one and try it first, just because it is so cheap and you may be over thinking it. The caps work by opening up and relieving the pressure into the overfill bottle when it reaches a certain point. A properly functioning cap that is installed correctly should not leak before it relieves the pressure into the bottle.

You can take the hose off and blow bubbles into the tank, and the radiator fill neck isn't damaged/clogged? you may even be able to return the cap and try a new one for free before looking further.

chaddwick2005

I took the hose off the radiator side and blew bubbles into the overflow tank.
I will try a new cap, just get them to replace it as manufacturer defected part.
But I am thinking that the fill neck maybe damaged, the po had one tab on the fill neck that stops the radiator cap at full close bent up and into the neck, that would cause the cap to seal harder against the neck, which would seal better if the neck was slightly bent.
But I will try a new cap first, but thought it was odd that it is happening to 2 of us on here using different company caps. Maybe just a big coincidence.
-CZ

Edit: I know the hose coupling on the fill neck for the overflow tank isn't clogged because I can see right through it.

djb383

As mentioned, be sure to closely check the neck of the rad for a hairline crack, nick, gouge in the plastic that could cause a leak/bad seal to the cap.

Fsher21

well that was an important part to include, what the PO did. Not really able to picture how you explained that bent piece, but that is probably a very good place to start. It could have warped the surface where the cap needs to seat...check that out before you get a cap, why did you do the entire cooling system but leave the old rad? I see you didnt list it but by complete overhaul I assumed it was also new.

chaddwick2005

Didn't include radiator, bc of budget, would've doubled it. Plus, I figure a good old flush of the radiator would help it.
Tomorrow night, next night of free time, I will inspect the filler neck with a "fine tooth pick", it maybe warped from the po, may be cracked, I don't. But thanks for all the feed back, steers me in a good direction.
-CZ

djb383

I know money is short but FWIW, +/-$110 will get a new OE style rad at most parts stores.

freegdr

did old cap leak .....put it back on....

Johnthepanpire

Stripped overflow bottle?

Bbasso

Yeah...
So I went to the Jeep parts counter today and paid $16.xx for a OE one. There is a big difference in the autozone VS OE.

Now to drive tomorrow in the 98 heat and see if it leaks.

FYI my radiator is jusst 3 months old, no cracks or damage of any kind.
I know for a fact it's the caps leaking.
the first 2-4 days they don't then they start to leak. POS chinese crap is not worthy of our American motors!

djb383

I believe '91 or '92 and up don't have a pressurized bottle....no threads to strip.

chaddwick2005

Old cap didn't leak, will explain later why, but tossed it as soon as I got the new one (garbage man has already came and gone)

Did inspect the fill neck and didn't find any hairline cracks to leak from but did find an area around where the cap seals that was either smacked with a hammer at some time or warped bad.



Here is my fill neck, the Green ring around the neck is where the cap looked like it actually sealed. Now the Red portion is where the neck is damaged and where the cap didn't seem to seal and then leak from.

So I went to the local hardware store, and purchased a 6"x6" sheet of 1/16" rubber membrane (used for plumbing gaskets) and cut out a 2" round donut, then slid that on the cap, so now the cap has a double seal. It is a little tougher to get the cap on and off, but the seal holds. Had the jeep idling for about 10 mins while Sea Foaming the engine, and there was no leak. So took the Jeep for a drive, watched the temp get to about 210 but stayed there, and when I got home, popped the hood and no leak. Looked at the recovery tank and noticed that there was actually more antifreeze in there than before (the line was about half way through the "F" in Full, and now it is above the Full name). So that proves that instead of the fluid leaking out of the cap, it is going into the recovery tank.

So now onto what the PO did, notice in the picture the Blue tab (it is the tab that stops the cap from further tightening, well the PO had that tab bent in towards the filler neck like the Light Blue shape shows. What this allowed was for the cap to be slid past the stop point, allowing more pressure to be applied to that side of the filler neck. Which fixed the PO's leaky problem I assume. Well when I put the new cap on (and tossed the old one), I straightened that tab back to its original position, which then made my new cap leak, resulting in my temporary double seal fix (until I have the funds to buy a new radiator, man weddings are expensive these days).

I will keep an eye on the cap the next couple of times I take it for drive, to see if it will leak after a week or too (don't drive Jeep that much, too nice here not to be riding the motorcycle, plus 35 mpg is better than 9). So if you don't hear back from, that's a good sign that the seal is holding.

Thanks to everyone on their suggestions, probably could have done it without you, but it would have taken me longer.

Thanks again,
-CZ

djb383

Since the cap is modified, in order to seal, the pressure release mechanism may have been affected as well as the coolant return to the rad as the motor cools. Keep close tabs on coolant level by frequently removing the rad cap, MOTOR COLD, and making sure coolant level is remaining at the top of the rad. Keep tabs on coolant level in the bottle as well as it must always have some coolant in it or else air will enter the system when the motor cools.

chaddwick2005

good points, will keep tabs on the levels.

chaddwick2005

so after a week of driving the jeep with the extra cap seal, my coolant levels are good. With the cap on and jeep running, I can watch the level in the overflow tank rise (with no leak from the cap), and then after shutting the jeep off and let it cool down, the level lowers. The radiator is always full. So this works as a fix.