Matt_75

So, after I got done with my HG job I still noticed a coolant smell in my engine bay immediately upon opening the hood after the car was warmed up. I assumed initially that it was just coolant burning off from areas I didn't clean from when the reserve tank blew from the bad HG. I did a solid burp after the HG as well. I also still noticed I was loosing a subtle amount of coolant in the reserve tank. I topped it off to max about once a week for the last three weeks or so, thinking maybe there was air some how still trapped in the system. It was loosing maybe a quarter inch of coolant from the max line.

Finally today, I decided to inspect the radiator and hoses closely. I couldn't see anything with the hoses, but below is what I found with the radiator. I was wondering if that crack was caused by me somehow, a stone through the grill or just wear and tear? Also you can see the wet seams next to the cap and no it is not a little spill over by me from feeling the over flow.

And yes, that is an after market fan that has the sticker saying caution keep hands away on it. Ignore the last half of the video. I was trying to get the inside seam but couldn't get my phone down there.

OEM parts are on order from Majestic.

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ezone

Average. Some crack at the stamped label pad area too, when equipped.
Opposite of the top hose tells me it's fatigued the nylon from thermal cycling and the rather sudden hot blast that part of the tank receives when the thermostat opens.
COULD have been done if it overheated too. If yours never overheated, it's probably just coincidence.


CSB: Back in the late 80s, Mazda had a stat with a tiny thermostat valve that opened early/lower temp to sort of slowly preheat the plastic radiator tank before the main section of the stat opened and blasted it with HOT water. Purpose was to keep from cracking radiators.

Matt_75

Yeah, car's never overheated. Could the crack have happened the one time the cylinder pressure blasted fluid out the reserve tank? AFAIK, the reserve only pressurized once and filled to the top and then I did the HG job. You can also see dried fluid on there probably from that one time. So now I'm thinking collateral damage from the blown HG. It's only a tiny pin hole wet when the cars warmed up with the engine running when I shine the flashlight in there.

Also, As far as I can remember, I never smelled any coolant in the engine bay before the HG blew.

ezone

No.
The radiator cap limits the pressure, vents at 16 PSI or so..
Unless it was bad, the radiator never saw any more pressure than what it normally sees every time the engine warms up.


The reservoir is not a sealed unit, it cannot be pressurized....unless the radiator suddenly barfed fluid faster than the reservoir could vent.


From what I remember, the typical nylon composition the tanks are made of starts breaking down at around 270-290*F, so a really serious overheat event certainly can compromise the structural integrity.
(Can a rocket scientist double check these figures please?)
Almost always there would be steam erosion damage in the neck under the pressure cap if it managed to get this hot.




I think it's coincidence (I haven't had to suffer missing this with a head gasket repair yet).....or it got hotter than you thought when it pushed a bunch of liquid into the reservoir. Either way, a fresh radiator will fix it.

Matt_75

I really believe that's what happened when HG gave way. And if it got hotter than I thought, it never registered at the temp gauge. And if got hotter than I thought and warped the head that I didn't get machined, I'm thinking I would've noticed overheating problems already. Maybe not. IDK.

Doesn't matter at this point.

And that's exactly what it's going to get. Brand new OEM.

Matt_75

So my question to you ezone is do you really believe this is coincidence that it cracked very close to the upper rad hose or do you really think it some how overheated and I somehow missed it and it cracked this way because of the overheating that I never saw on the temp gauge?

I don't want no fluff fluff here. I just want your experienced opinion.

The crack actually starts at the center line of the upper hose and goes about 3 inches or so to the right as viewed in the video.

This is eating at me because I want to know the root cause of this problem. Was it overheating that incredibly I some how missed or was the coolant flowing with force that the overflow or cap couldn't handle and it cracked the rad?

Coincidence always bugs me, but I am accepting in certain situations. This is one of them if you really, in your expert opinion, think it could be coincidence.

Sorry. I'm a little OCD on these issues.

ezone

*I* think it's coincidence.....I have seen plenty that suffered worse engine damage (warped head) with no ill effects to the radiator AFAIK.


And I have seen the same radiator failure without your associated engine failure.
I've been seeing the same types of radiator failures for 20+ years, almost always at higher mileages (ever since plastic tanked radiators became the norm, and on far more brands than just Hondas).


Like I said in the first post, it seems "average" to me: The "rather sudden hot blast" happens after EVERY warmup of the cars life, the first time the stat opens after warmup.

You have a ~100*F+ rapid change happening right in one localized area of the tank EVERY time the engine goes through a warmup cycle...It's a localized hot spot for at least a brief period.
It takes a bit more time to get the rest of the tank up to the same temperature.

Take the same theory to an extreme: Heat a single spot in a pane of glass (or large glass bottle) with a blowtorch and see how long it lasts without breaking. The unequal heating causes unequal expansion rates in a rather brittle substance, thus causes breakage. If you heated the entire pane (or bottle) equally, it wouldn't break.


Just replace the radiator, you'll be fine.

Matt_75

Cool man. Sorry for the OCD. Thanks for taking the time to type that out.