I have not been on here for a while but as always I NEED SOME HELP! 3.4 not a 2.4 sorry for the typo

The radiator literally just blew up in my 96 with 250k on it. I found another thread but wanted to share my experience and hope for some input. I bought the rig with 220 on it, replaced the T-Stat, and a couple heater hoses is all. Was in the hills just driving around slowly on some old logging roads. Going up hill but not "climbing" anything. Outside temp was 40.

Just pulled (slow as in under 5mph eased up it no problem) short steep little grade and I smelled coolant. Temp gauge was a little above half (half is normal) so checked around no leaks, not hot, coolant in overflow, nothing bubbling, nothing could be found.

Started driving and temp dropped to mid level then I hit another steep little grade and the temp started climbing and held at 3/4 but not even close to red. Then it started to climb a little more on temp gauge, told my buddy I'm turning around and BOOM coolant steam all over.

Opened the hood and the top radiator hose is blown off with plastic sheared off from the radiator still inside, the vent line blew off with the plastic still in it also. The entire top of the radiator was opened like a tuna can. Limped out of the mountains and then trailer to home. Radiator has cracks in bottom and side, so it hold no water at all.

Why, how, WTH, not a glitch, never hot, runs perfect (even now), fan clutch is good. Obviously I will put a new radiator in, but I don't want to blow it up either. It appears the radiator in it may be aftermarket due to appearance and nothing Toyota on it (don't know how to tell if factory) Please help or provide any info you can.

On the stock water temp gauge, you should really never see it climb past the half-way mark. If the gauge was 3/4 up, you were overheating. Something was definitely wrong with your cooling system. Let's just hope your radiator was clogged up and that was the culprit.

If you replaced your thermostat, did you use OEM? Did you put the jiggle valve at the 6 o'clock position pointing downward? How do you know the fan clutch is good? Did you replace it recently? If so, did you buy one made by Aisin, which is the company that makes the OEM one.

If I were you, do some research on radiator replacements. I went OEM for my rig, but many have used Denso and Koyo and are happy with them. If you didn't install an OEM thermostat, junk the one you put in there and get an OEM one. You obviously need a new upper radiator hose but I'd get a new lower hose as well.

If you haven't considered it yet, get yourself a Scan Gauge or use the Torque Pro app with a bluetooth OBD II reader and be able to monitor your coolant temps a little more accurately.

This also might be the opportune time to install an external trans cooler.

Here's a video that can help you out:

Thanks for the reply.

I checked the fan clutch by running it and paper testing it. I ran it for about 10 minutes after filling the block with water. It was warming up but did not get to operating temp. Had water running into radiator, but did not get warm enough for T-stat to open. I just did not want to run it much longer. Motor oil is perfectly clean, and no vapor out the exhaust. (At least not yet) Hoping it is not a head Gasket.

Looked at adding a cooler, but I'm not a crazy thrash it off road driver. Just go hunting and use my PU if I need to pull anything. I know I will at least throw an in line magnetic filter in it.

Bouncing off the walls worried about a blown head gasket. Went out....fired it up...ran it until it started pumping water out the top hose. No extra exhaust vapor...normal vapor (35 degrees out) reduced as it warmed up...nothing in the oil.

Help a brother out...WTH with a radiator just blowing up?? I have been around motors my entire life, cars, boats, excavators/cats/hoes, tractors, generators, semi trucks, air planes, bikes, you name it I have probably ran it or been around it. Yes even huge rotary engines from the 50's!!

I have heard of it but never experienced or was ever able to be shown one ....EVER...a radiator just blowing up...WTH???? Lost hoses, blew off caps, burst lines, leaks, damages, burned motors up, but the radiator coming apart for no apparent reason??? NEVER!!!!

I rant every day about how Toyota is bullet proof. In fact the guy who came and got me out of the hills with a DODGE commented about me and my Toyota Love. He (also farmer and around tons of engines) did not believe me and had to see it. "Holy Sh*& I have never seen that in my life. I didnt know that could even happen")

First thing - why did the radiator explode? The radiator cap should have relieved before the pressure got high enough to blow the radiator the way you describe. It sounds like it may have relieved some if you smelled coolant. Perhaps wrong or defective radiator cap. Definitely replace cap when you install new radiator. FYI - I just installed new Denso radiator and Gates cap sourced from RockAuto and was happy enough.

Second thing - why did the pressure get that high? Lots of normal potential culprits - low level engine coolant, bad fan clutch (as previously discussed), wrong anti-freeze/water ratio, bad head gasket, air/blockage in system, defective/wrong thermostat, etc.

Finally, why did your temp gauge not hit the roof? Sounds like it was climbing so maybe operating normally. Did your CEL light? Regardless, recommend you check for both active and pending codes.

Buckaroo

For whatever reasons, Toyota cheaped out on the radiator in the 3rd gen 4Runner(and the matching Tacoma).
You didn't really expect a plastic-tanked radiator to last 20 years, did you?
Well...now you know.
Best scenario is that the cap failed and didn't relieve pressure, and that the initial coolant smell was the first vapor out of the slowly growing fracture.
Like the others said, new rad, T_stat, cap...all OEM.

Is there a non plastic radiator available?

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Its not any BETTER. Just get some oem in there asap. If it makes you feel better i saw 3/4 on the analog gauge and my rig is 20k miles after the fact going strong. I immediately got a oem amazon fan clutch and a scan gauge ii. I caused my overheat by putting a jetski on the front and not having enough airflow over the radiator. Moving the jetski fixed it.

I have seen exactly what you describe on an ol mazda 626 i had after hs. Driving into the hills of Vermont, it blew the radiator the same exact way. I was not experienced and ended up overheating it and warping the head before i knew better. Just saying you might be just fine.

This recently happened to me. Top of the tank cracked and blew out. I had smelled coolant before that and didn't see anything. When I took the cap off, I noticed that it had broke completely and failed. Causing too much pressure to build and blow out the tank. I put in a denso radiator, which looked identical to oem. But I went oem on thermostat and gasket and the radiator cap and fluid. My Temps were a little high before the blowout also. Now they are perfect. I am blaming it on a failed cap. Only 150k on mine. But I guess it is 16 years old and has been an Arizona vehicle. That's the longest a radiator has lasted for me. Lol

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Gotta agree...plastic tank radiators suck for this reason....BUT...it was 20 years old.

Supposedly, the smallest rad (3rd gens have 3 sizes with 6 variations depending on MT vs. AT....and those are just the ones I know about; and first gen Tacoma radiators are direct fits) can be had in an all aluminum version. Someone here recently posted a link to it. Less than $200 IIRC.

Got any pics? It likely started with a small stress crack somewhere and eventually gave out. In theory, the radiator cap should protect against overpressure, but if your radiator was compromised then it was just a matter of time.

I hate plastic radiators too, but no choice as all modern vehicles use plastic everything: radiators, valve covers, oil pans, etc...

Pulled the radiator today. (Took an entire 15 minutes!!! LOL) Here is what it looks like. It has to have some other cracks as it hold almost no water. (less than a quart came out when removed lower hose) Radiator looked in really good shape as far as internally and cooling fins. Very clean!

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Any time I've seen a radiator explode it's due to a blown head gasket, I've seen this happen to american an asian cars alike. You should definitely go to NAPA and get a block test kit, that way you will know for sure.

You nailed it! Crazy how we learn something new all the time. We don't have the ability to rent tools so I bought a tester. Fluid color would not change while idling, but would turn a light bluish green color at fast idle. It took several minutes to get it to change at all, and I could never get it to turn yellow or even yellowish no matter how long I pulled air through the test liquid. It took about a minute at 3k to get it to change at all. I did it twice and ended up with the same color and timing of change. Obviously I have something going on, but hoping it is so minor I can "fix it in a can". I've seen blown head gaskets, but they were always obvious and never lost a radiator.

So now I'm going to dump some Blue Devil in it and see how it turns out. If it works great if not I know where it's at anyway. Will let everyone know how it turns out. Thanks for all the help everyone!

So here is where I'm at. Put in a new Denso radiator...Amazon amazingly was the best price to my door. Member A.Wilson013 was awesome and shipped me some testing tools. Tested the cylinders for pressure and I think they are great. All were right around 180-190 psi.

Then I did a leak down on the coolant system. Nothing moved at 12psi, so I jacked it up to 20. Started leaking at several hose fittings after an hour or so. Obviously way too much pressure. Fired it up and ran like a top.

Dumped in the Blue Devil snake oil and then added some new coolant. I dumped half a gallon of the Blue Devil/Distilled water back in with the new coolant. Tested it again with the gas system with a different result. Tested at idle and at 3000k for 1.5 minute pulling air through the solution.
Before test:

After Test: The first time after radiator blew up it turned a very light bluish green after a minute at 3k. This time no change.

Temp after about 40 minutes:
Well Photobucket sucks and I can't get the other pictures. But the temp was just under half and normal. I drove it up the hill and gained 1500' in 4 miles at 20-30mph. Perfect temp at the top.

So was it the snake oil or was there never a problem?