What causes multiple coolant leaks at once?

[DHC6twinotter]

Hey all,

So, I've got a couple of coolant leaks that just sprung up on me. The leaks are at the radiator cap and the coolant bypass hose on the front of the intake plenum. Now I know just a leaking radiator cap or bypass hose in itself isn't that big a deal and are easy to replace. What I don't understand is why would they both start leaking at once? Coincidence? :headscratch:

Temperatures did dip down around 15 or so a few nights back, but I have roughly a 60/40 mix of coolant/water so I don't think that would cause any harm. Coolant was changed a little over a year ago. I replaced the water pump and thermostat about 45k ago.

I don't know whether or not this could be related, but I've also been hearing some "popping" noises from the heater core area. Not really the slushy noise that folks usually associate with air in the core, but I suppose air could be in there. Air in the line could also be affecting my IAC valve which may explain why I have rapidly fluctuating RPMs at idle or when coasting. This has been going on for several weeks, before the leaks appeared earlier today. Again, I don't know if this is a separate matter, or if it has anything to do with my leaks. Just thought I would mention it for the sake of diagnoses.

Anyways, I was just curious as to what you all thought. I hate cooling systems, but this is probably due more to my ignorance on the subject than anything else.

Thanks in advance for any help with these small leaks. :D

[slosurfer]

Could just be that your leaking radiator cap was causing some weird pressure symptoms and the weak spot was where your other leak was. :headscratch: I'm still kind of new with the whole coolant system as well, but I do know that a leaking radiator cap can cause all sorts of weird symptoms and problems. I've learned this from the van forum I'm on, as these vans have an iffy cooling system that needs to stay in top condition.

[CJM]

I would agree with slo, it was probably already a weak spit.

[DHC6twinotter]

I'll check again to make sure there aren't any cracks in the hose. It does appear that the coolant leaking out of the hose is coming from where the hose connects to the pipe that runs under the intake plenum, but I'll double check for any cracks.

Is there any way a leaking hose would cause a leak at the cap? Or any way a leaking cap would cause a hose to leak?

Would a blockage in my cooling system cause the pressure to rise and come out of the ratiater cap and/or hoses? Would the overflow tank compensate for any excesive pressure buildup?

Sorry, these are probably newb questions, but I guess I'm a newb with cooling systems. :hillbill:

I'll take a pic tomorrow.

Thanks for the input Chris and CJM! :thumbup:

[slosurfer]

If your cap is leaking, replace it for sure, because if it's leaking coolant out then it's also letting air in and not letting the system be pressurized like it's supposed to.

Replace the cap, check that one hose and clamp, top off, and burp the system for safe measure. Then keep an eye on it. :thumbup:

[CJM]

I agree with Chris, check out everything and replace the cap and hoseclamp and or hose and watch it closely.

If you cant afford a new rad (if it is leaking) some barrs stop leak will fix it in most cases but it may mess with the coolant system itself. However for future reference to anyone reading: barrs stop leak fixed the headgasket on a pos chevy cavalier I worked on 2 years back lol.

[corax]

Barrs stop leak on my old p/u clogged the tube going to the overflow so pressure was never able to bleed off until the radiator split at the top tank seam about 30 miles from home :D

a stuck radiator cap can cause over-pressurization in the cooling system leading to split hoses or hoses popping off. Also, jsut make sure the overflow hose is clear.

[DHC6twinotter]

Thanks guys.

I pulled off my overflow hose, and it looks fine. I'm going to buy a new cap tomorrow after church. Hopefully that will help. The radiator itself appears to be fine. How long do caps usually last? I replaced both the cap and radiator about 70k ago.

So, to further my understanding, what causes over-pressurization to begin with? Is this normal and just a sign of the coolant warming (greater heat=greater pressure), or is this a sign of some other issue?

[CJM]

Barrs stop leak on my old p/u clogged the tube going to the overflow so pressure was never able to bleed off until the radiator split at the top tank seam about 30 miles from home :D

a stuck radiator cap can cause over-pressurization in the cooling system leading to split hoses or hoses popping off. Also, jsut make sure the overflow hose is clear.


How much did you add lol? I added only a little bit and no issues yet on that pos cavalier in like 60k.

[corax]

So, to further my understanding, what causes over-pressurization to begin with? Is this normal and just a sign of the coolant warming (greater heat=greater pressure), or is this a sign of some other issue?


The radiator cap will only allow a certain amount of pressure to build up before the center part lifts off its seal and lets pressure bleed down - the spring in the middle of it is calibrated to hold a certain pressure. So the cap is really the only thing (besides a restricted overflow hose) that can let pressure build too high.

[DHC6twinotter]

The radiator cap will only allow a certain amount of pressure to build up before the center part lifts off its seal and lets pressure bleed down - the spring in the middle of it is calibrated to hold a certain pressure. So the cap is really the only thing (besides a restricted overflow hose) that can let pressure build too high.


That may explain why I noticed a bit of coolant on top of my cap. I never knew the little center piece opens up to vent to the atmosphere.

I love learning new stuff!

[corax]

The radiator cap will only allow a certain amount of pressure to build up before the center part lifts off its seal and lets pressure bleed down - the spring in the middle of it is calibrated to hold a certain pressure. So the cap is really the only thing (besides a restricted overflow hose) that can let pressure build too high.


That may explain why I noticed a bit of coolant on top of my cap. I never knew the little center piece opens up to vent to the atmosphere.

I love learning new stuff!



Actually it doesn't vent to the atmosphere (or shouldn't anyway) that little nub is just a byproduct of the design. The smaller center piece (only visible with the cap off) with the round rubber gasket thing is the part that gets pushed up by cooling system pressure, which lets coolant flow past and the only place for it to go is out the side into the overflow hose / bottle

[DHC6twinotter]

Actually it doesn't vent to the atmosphere (or shouldn't anyway) that little nub is just a byproduct of the design. The smaller center piece (only visible with the cap off) with the round rubber gasket thing is the part that gets pushed up by cooling system pressure, which lets coolant flow past and the only place for it to go is out the side into the overflow hose / bottle


Oh, ok. That makes sense. Thanks!

[DHC6twinotter]

So, I put a new cap on, and this seems to have fixed it. I'm going to keep an eye on it for the next few days.

I never would have figured a bad cap would cause leaks elsewhere. Is there a way to tell where the old cap failed? From looking at it, there doesn't seem to be any visible problems with it.

I feel dumb about starting a thread over a bad radiator cap. Oh well, at least I learned stuff. :hillbill:

Thanks guys!

[slosurfer]

I know a lot of times there are no obvious signs that it failed somewhere, sometimes it just quit sealing right. If I hadn't of done all the research for the van, I wouldn't have known all the problems a faulty cap could cause. This thread will definately come in handy for someone else down the road. :thumbup:

[DHC6twinotter]

Well, looks like the cap wasn't the culprit after all. The new cap doesn't seem to be leaking, but my hose is still leaking. I'm in Nebraska right now, but when I get back home, I'll have to check my hose and clamps again.

It still kinda baffles me how two things can start leaking at once.Oh well. :hillbill:

I hate cooling systems. Maybe I should just buy an old 21 or 23 window VW van. :king:

[CJM]

You need to pressure test it honestly, you can buy one for like 30-50 bucks and do it yourself.

[Seanz0rz]

I hate cooling systems. Maybe I should just buy an old 21 or 23 window VW van. :king:


air cooled vw ftw!!!! im about to buy a type 3!

[slosurfer]

I hate cooling systems. Maybe I should just buy an old 21 or 23 window VW van. :king:


I hope you like pulling engines and working on them then. :flipoff: :laugh:

[YotaFun]

I hate cooling systems. Maybe I should just buy an old 21 or 23 window VW van. :king:


You and me both!
But getting a VW necessarily is not the way to go.
Ask me how I know......

[DHC6twinotter]

haha...true. I've heard of cooling issues with the VW vans. If the seal around the rear door isn't just right, the engine can overheat.

I think the record for pulling an air cooled VW motor was around a minute and a half. I guess it's a competition somewhere.

My brother and I almost bought a '66 11 window bus a while ago. Needed lots of work though. :(

CJM--I'll look into getting a pressure tester. Thanks!

[DHC6twinotter]

So, I fixed the leaking hose a few weeks back. I thought all was well. Last week, I jumped somebody's car and noticed some coolant around my radiator cap again (the new one).

Over the course of the last week, I haven't driven much (no need to go anywhere really), but I've kept an eye on the temp gauge during the little bit I have driven.

Now today, I checked my coolant level in the overflow container. It was empty. Temp gauge was fine today though, and never got above normal. I'll have to add some coolant and try to pinpoint where the leak is coming from.

I'm about to pull my hair out. :hillbill: :confused:

[CJM]

Pressure tester man, will pinpoint it in minutes.

[DHC6twinotter]

So, I ran around town yesterday and today to find a pressure tester that either wasn't broke or would fit my radiator. Finally found one at Advance Auto's loan a tool deal (worth 159.00! :confused:)

Anyways, I tested the system with the engine cold. I built up about 14 psi, which is just above what my cap was rated at. No leaks and it held pressure. I then got the engine temperature up to normal, shut it off, then tested. No audible leaks, but the pressure dropped very slowly. It took about 40 minutes for the pressure to go from 14psi to 0. I guessing this is due more to the engine cooling and pressure dropping as a result of that, and not from any leaks?

I tested my new cap. It seems like it would not hold pressure. All the air I pumped in would go out the little hole in the side.

So, either my tester wasn't an exact fit for my cap, my new cap was the culprit, or the pipe that goes off to the overflow tank is leaking (which I don't think could have been tested with a pressure tester). What do you all think? :headscratch:

[Seanz0rz]

find a store with a great return policy, test a new cap

[DHC6twinotter]

find a store with a great return policy, test a new cap


I picked one up from Toyota. :king: I'll test it tomorrow.

Actually, the parts manager at the local Toyota dealership (Rick Hendrick Toyota) was really cool. I wasn't sure what time they closed and ended up walking in after they had closed. In one of the hall ways, I ran across the parts manager, who I hadn't seen in 3 years. He recognized me from the limited number of times we had met back when I used to work parts delivery for another dealership in town back in the day. I asked what time they opened tomorrow, and he asked me what I needed. I told him, and he said to hang on. He came back with my part, and gave me a discount. I paid him cash, minus the nickel I didn't have. Then we talked in his office for like 15 minutes about Land Cruisers and 4Runners. Anyways, supper cool guy, and I just wanted to give props to the local dealership. :clap:

[DHC6twinotter]

So, I tested the Toyota cap, and it holds pressure up to about 16-17psi. This is a bit over spec, but is that fine? I checked the part number on the cap, and it's correct.

Looks like my old "new" cap was bad. http://www.expeditionportal.com/forum/images/smilies/REOutShootinghunter01.gif

[CJM]

Should be fine, run with it.

[DHC6twinotter]

I drove across town today to pick up a CDL booklet, and so far, I haven't had any issues with my cooling system.

I'm still going to keep an eye on it though...I'm not conviced yet. Last time I thought I had it fixed, and it started leaking after a week. :confused:

Thanks for all the help guys. Broke stuff isn't fun, but it's also a great chance to learn new things. :thumbup:

[Osiris]

If you have another leak at the filler cap in a week or two again, then I would look at the filler hole on the radiator to make sure that is not damaged or dented up so the caps can make a good seal. I hope you fixed it though.