Too much flex.....unibody that is. Radiator leaks?

JJsTJ · **Posted:** Mon Oct 20, 2008 11:52 am

I suspect that i might be getting too much unibody flex. I say this because I have popped the tank to core seal on two radiators in the past several months, both while wheeling very large boulders or ledges. (once in Moab on the large ledges on Kane Creek and a week ago in Big Bear on John Bull where I was posing on large boulders for the camera)

My theory is that the front half of the unibody, forward of the axle, is flexing and causing the radiator mount which is bolted to it to flex. The radiator is mounted via rubber bushings attached to the plastic tanks and those are bolted to the rad support. If the front unibody flexes too much, it takes the tanks with it and with both sides moving in opposite directions it pulls them just enough to compromise the seals between tank and core.

I mention this to give others the opportunity to know of the possible problem and maybe we can discuss a way to prevent it from happening in the future. I would also like to discuss the possibility of custom metal radiators, and getting rid of the plastic crap.

Fulltimer · **Posted:** Mon Oct 20, 2008 12:15 pm

[quote="JJsKJ"]I suspect that i might be getting too much unibody flex. I say this because I have popped the tank to core seal on two radiators in the past several months, both while wheeling very large boulders or ledges. (once in Moab on the large ledges on Kane Creek and a week ago in Big Bear on John Bull where I was posing on large boulders for the camera)

My theory is that the front half of the unibody, forward of the axle, is flexing and causing the radiator mount which is bolted to it to flex. The radiator is mounted via rubber bushings attached to the plastic tanks and those are bolted to the rad support. If the front unibody flexes too much, it takes the tanks with it and with both sides moving in opposite directions it pulls them just enough to compromise the seals between tank and core.

I mention this to give others the opportunity to know of the possible problem and maybe we can discuss a way to prevent it from happening in the future. I would also like to discuss the possibility of custom metal radiators, and getting rid of the plastic crap.[/quote]

The bean counters are laughing right now! Just a bunch of junk. If I remember right there are some metals ones out there. But, depending on how much the front flexes it could cause a problem with the metal ones also. Maybe you will luck out and have somebody post that they are using one on a SFA KJ. Good luck!

Terry

tjkj2002 · **Posted:** Mon Oct 20, 2008 12:20 pm

You are getting to much front unibody flex.Below is a pic with the front 2 engine cradle crossmembers that were cut off for your SFA swap(labeled #1 and #2),those 2 crossmembers are a main source of front unibody support and rigitity.When the time comes we have already addressed this problem for my SFA swap,rather I insisted on at least one crossmember being put back in(higher up as not to be in the way of the axle).

JJsTJ · **Posted:** Mon Oct 20, 2008 12:28 pm

Troy, Got any pics, drawings, etc of your fix?

I am looking at possibly adding in some cross bracing for the front both above and below the engine. A support running from shock tower to shock tower and possibly froward to a support off the rad support and then a cross member in the front from just behind the lower rad support tied in to where the front bumper mounts are. I'll get pics of where I'm talking about later today.

tjkj2002 · **Posted:** Mon Oct 20, 2008 12:36 pm

JJsKJ wrote:

Troy, Got any pics, drawings, etc of your fix?

I am looking at possibly adding in some cross bracing for the front both above and below the engine. A support running from shock tower to shock tower and possibly froward to a support off the rad support and then a cross member in the front from just behind the lower rad support tied in to where the front bumper mounts are. I'll get pics of where I'm talking about later today.

Well right now they are in Marty's head.We are building a whole new engine cradle that will have the steering box mount on it and the front cross member will be put in,up high and ties the steering box mount to the otherside of the engine cradle and will most likely be using 1.5" DOM.We also thought about adding a rear cross member but would be weak and to complex to make room for the control arm/oil pan/exhuast.The "strut" brace is a good idea,might have to run that by Marty,dangit more pricey DOM to purchase :evil:

.

With that being said I also have the ARB bumber which the base plate addes alot of structual support to the front end by how it is attached,a bit more then your AllJ's bumber(not knocking the bumber at all,just saying) so one cross member shopuld be enough for me.

Diggerfreek · **Posted:** Mon Oct 20, 2008 7:02 pm

the strut brace should help give some rigidity back but it may not be enough

ATXKJ · **Posted:** Mon Oct 20, 2008 7:36 pm

Try one of Summit's or Jeg's universal fit aluminum radiators - mount on some flexi type mounts so that the frame flex doesn't kill it.

http://store.summitracing.com/egnsearch.asp?Ntt=radiator&N=700+400001+4294810996+115+4294839040&NeXID=5&Ntk=KeywordSearch

http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&N=4294935220&Ne=1147708&Ntt=radiator&Ntk=all&Nty=1&D=radiator&Ntx=mode%2Bmatchallany&Dx=mode%2Bmatchallany

offroadohio · **Posted:** Mon Oct 20, 2008 7:42 pm

im with tjkj2002, definately need to replace the cross members you lost.

doesnt need to be big and bulky just strong enough to hold the rails togather.

Maybe some tubing that can tuck up nice and close to the oil pan???

Something like this would probably be enough (of course this is a pic I found online, and is obviously for a full framed vehicle)

Guest · **Posted:** Mon Oct 20, 2008 10:32 pm

Wonder how likely it is that that's what killed my 2nd radiator?

Not that I've hacked anything out of my front end or anything

ohv_kj · **Posted:** Mon Oct 20, 2008 10:52 pm

i made a cross member that goes under the crank( harmonic balencer) it seems to hold pretty well

JJsTJ · **Posted:** Tue Oct 21, 2008 8:33 am

ohv_kj wrote:

i made a cross member that goes under the crank( harmonic balencer) it seems to hold pretty well

Pics?

ARBSeth · **Posted:** Mon Nov 10, 2008 2:29 pm

Mine broke twice...Troy, don't count on it holding just because of the 3450110's cross frame.
Man, that was a pain. I had to carry that sealant with me at the end. Changed it out before I sold it, though.

elephantrider · **Posted:** Tue Nov 11, 2008 8:25 am

seth do you ever hear from whoever bought
the kj ?

JJsTJ · **Posted:** Tue Nov 11, 2008 9:24 am

ARBSeth wrote:

Mine broke twice...Troy, don't count on it holding just because of the 3450110's cross frame.
Man, that was a pain. I had to carry that sealant with me at the end. Changed it out before I sold it, though.

Your radiator broke or the cross frame broke?!?

ARBSeth · **Posted:** Tue Nov 11, 2008 12:20 pm

Radiator.

ohv_kj · **Posted:** Tue Dec 16, 2008 1:11 am

i found what's keeping mine from doing the same thing...i do have that brace but the front hitch is a major contributor i believe...that said...i'm going to do a little experiment...i am taking off the brace and attaching a string from rail to rail to see where the flex in the uni-body is...if i don't get any...i would have to presume it is because of the front hitch

JJsTJ · **Posted:** Tue Dec 16, 2008 9:12 am

I would think that my ALL J bumper would act similarily as the hitch since it ties into the same mounting points as the hitch Plus a few other spots.

IF it also tied into the crossmember that is directly Behind the bumper, perhaps it would work better as a crossmember then? Of course I don't think that would be enough. I think it still needs another crossmember beneath the engine tying the factory engine cradle rails back together.

I will be agressively persuing a fix after the holidays.....it is tough trying to keep off the big rocks and I just know I am going to pop another radiator soon.

Too much flex.....unibody that is. Radiator leaks?

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