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Jeep Liberty KJ and KK (2002 - 2012) Technical forum for all Jeep Liberty (also known as Cherokee in non-US markets) vehicles.

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  #16  
Old January 15th, 2018, 11:16
CJR CJR is offline
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Re: Bent valves and wiped cam?

Ecomike,

Old school engineering dictates there must be clearance between valves and piston. Unfortunately, recent engines (i.e. Mitsubishi/Chrysler) use zero clearance between valve/piston. Eventually, thru thermal growth, etc. valves start hitting pistons which causes valve guide wear, bent valves, cracked pistons, cracked heads, etc. Years ago, I rebuilt/modified a 3.0L V-6 Mitsubishi engine out of a Plymouth Minivan that had zero valve/piston clearance. During fit-up I used modelling clay on the piston to check the valve/piston clearance and I discovered the zero clearance. Old engineering principles(i.e. GM and engineering practice) always had 0.080-0.1" valve/piston clearance to allow for the valve's thermal growth. My solution was to jnstall custom made thicker copper gaskets, measure the valve/piston clearance to insure I had the 0.08-0.1" valve/piston clearance and button it up. That engine now has about 50,000-75,000 miles on it and runs better than the original configuration.

Hope this helps.

Best regards,

CJR
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  #17  
Old January 15th, 2018, 13:07
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Ecomike Ecomike is offline
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Re: Bent valves and wiped cam?

CLR, thanks for the info.

Green Mesa,

I did a few hours of digging on line, and the coolant story today is a nightmare, of many different formulas, claiming blue skies, and Godzilla risks.... of switching, etc....

Way too much to repost and discuss here in this thread. What I do know is the coolant did not bend 2 valves 2-3 days after those clowns replaced the head gaskets. It was already using coolant (head gasket issue), before my son added the old silcate based formula. One thing I can not fathom is why they all call them "A" acid based formulas when the pH is highly alkaline, not acidic. There is no history on where the insane use of the word acid came from in the acronym formula names. The old formula had a pH 10.5-11, Highly basic, not acidic. But every web site on the planet now says the old formula was IAT, Inorganic Acid Technology, LMAFIA!!!!

All I know is adding bars-leaks fiber pellets and using the old high pH silicate formula has worked for 8-10 years on all my rigs with out draining!!! Only water pumps I ever killed where 2 cheap china bearing, 3 month old junk ones for AZ, LOL. Only radiators I ever lost/replaced, were due to POS plastic tanks in the last 40 years. My 85 Cherokee, diesel still has the OEM radiator in it, LOL.

So back on topic, how does a bent valve stem wipe the cam lobe when there is a hydraulic tappet between them?
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  #18  
Old January 15th, 2018, 13:30
CJR CJR is offline
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Re: Bent valves and wiped cam?

Ecomike,

After posting my reply to you, I recalled that when I searched for zero-clearance valve/piston engine problems, Chrysler engines came up as being plagued with bent valves,worn valve guides, cracked pistons, cracked heads, etc. On pushrod engines, valve resistance (i.e. caused by piston contact and bending valves, valve guide wear, etc. ) is fed back by the pushrods to the cam lobes. After awhile, the cam lobes wear down excessively.

Best regards,

CJR
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  #19  
Old January 15th, 2018, 14:22
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Green Mesa XJ Green Mesa XJ is offline
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Bent valves and wiped cam?

The post from the kJ seemed to think the damage to the cam was done while the oil was diluted with coolant.

Far as the coolant debate goes Im not an evangelist for any of the new formulas, which ever coolant your son is going to run Id say flush all the old stuff out until hes only running one or the other. Mixing HOAT with regular antifreeze is supposed to cause a bad chemical reaction.




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  #20  
Old January 15th, 2018, 17:03
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Ecomike Ecomike is offline
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Re: Bent valves and wiped cam?

Playing devils advocate, the coolant did not bend the valve.

Also they are assuming the coolant leaked on the cam shaft, which I seriously doubt since the head was not cracked. While I got no confirmation as to where the coolant leaked, my money is on a leak through the head gasket into the combustion chamber (causing the original miss fire) and out the exhaust, but I have no proof or confirmation where the head gasket was leaking.

In fact the head gasket leak was fixed the first time in the shop, and nothing else.

At that time they did what they called a valve job for extra $$$$ since they had the head off (sales pitch they did my on my son).

2-3 days later it had 2 bent valves and no compression on 2 cyls. I think they forked up the service work and its now a ticking time bomb.

Quote:
Originally Posted by Green Mesa XJ View Post
The post from the kJ seemed to think the damage to the cam was done while the oil was diluted with coolant.

Far as the coolant debate goes Im not an evangelist for any of the new formulas, which ever coolant your son is going to run Id say flush all the old stuff out until hes only running one or the other. Mixing HOAT with regular antifreeze is supposed to cause a bad chemical reaction.




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  #21  
Old January 15th, 2018, 17:08
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Ecomike Ecomike is offline
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Re: Bent valves and wiped cam?

If, as I think, the two coolants operate at 2 different pHs, that is likely the case, however the jeep dealership he bought it from was not even using synthetic oil on the oil changes. So WTF knows what coolant they were using? It was used Jeep dealership.

If the pH of old style coolant drops from 10.5-11 down to under a pH of 10, it will precipitate a glass film on the heat exchange surfaces.

I have yet to find the operating pH on the newer coolants.

Easy enough to test with a pH meter, a glass beaker, stir rod, and watch to see if anything precipitates when they are mixed.

Quote:
Originally Posted by Green Mesa XJ View Post
The post from the kJ seemed to think the damage to the cam was done while the oil was diluted with coolant.

Far as the coolant debate goes I’m not an evangelist for any of the new formulas, which ever coolant your son is going to run I’d say flush all the old stuff out until he’s only running one or the other. Mixing HOAT with regular antifreeze is supposed to cause a bad chemical reaction.




Sent from my iPhone using Tapatalk
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #22  
Old January 15th, 2018, 17:14
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Ecomike Ecomike is offline
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Re: Bent valves and wiped cam?

So why did only two valve stems get bent? If it jumped time, wouldn't more of them have been damaged?

I read that the valve seats are sintered steel, pressed into the Aluminum head, and they are known to come loose and cause the loss of compression!!! Perhaps wiped lobes and bent valves as well? But the machine shop should have caught that!!!
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #23  
Old January 15th, 2018, 18:47
trippled trippled is offline
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Re: Bent valves and wiped cam?

Have you actually seen the head? From what you describe it sounds like the valves stuck in the guide. If it went long enough I suppose it could maybe cause the cam to go flat and if they eventually hung open could have hit the piston and bent the valve. But without anyone seeing anything it's pretty unlikely you will get a definitive answer. Yes, pretty much everything now is an interference engine. If a valve hangs open when it shouldn't it's probably gonna bend.

Coolant probably won't do it. You don't get synthetic unless you pay more for it. Put the coolant in it that's supposed to be in it.
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  #24  
Old January 16th, 2018, 12:45
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Vanimal Vanimal is offline
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Re: Bent valves and wiped cam?

a wiped cam will not bend valves as a direct result. A wiped cam decreases valve travel, so it would be LESS likely to bend. Also, unless the valve broke off and was floating around the cyl, i highly doubt it damaged the pistons enough to matter whatsoever.
However, if the cam is wiped, all that metal went somewhere, and that somewhere is in your bearings. That motor will have a significantly shorter lifespan IMO.
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