I have been using auto rx in my cars for the last couple of years. As an empiracist, I need to really show results based on actual studies that I conduct. I have used autorx on 4 different cars. 1. 2003 Honda Oddessy. 2. 2000 dodge stratus (6cyl) 3. 2002 Dodge Intrepid (2.7L). 4. 2000 Chrysler Concord (2.7L).
The results have been interesting. On the Honda and dodge stratus, the results have matched reported results on this web site. All sludge is cleaned up and the engines look spotless. How do I know? I remove the valve covers and cut open the oil filters. Why? Because I am a complulsive nut.
However, on the Chrysler 2.7L engines I encountered perplexing results!
Why buy cars like this? Well, I have kids in college and i buy cheap cars at auction, primarily thru Adessa Auctions which offers warranties on their repos. I always look under the oil filler cap for sludge as repos are notorious for poor maintenance. All looked good when I bought them.
The 2002 intrepid started whistling when it was cold. When i called the dealer about it, they said the hydraulic chain tensioner was going bad, probably because of sludge due to poor maintenance. That's when I found autorx on the internet and used it on all my cars.
I looked at the inside of the valve covers on the Intrepid before I added autoRx and they were covered with at least 1/4 inch of sludge. I did two treatments,but the whistling was still there. The 2000 concorde had about 3/8 of sludge but no whistle. After 2 treatments, I removed the valve covers again. The 2002 intrepid was like new and sludge free. Unfortunately, the hydraulic chain tensioner was beyond the max mark and the timing chain was slapping and making a ticking noise. The dealer said I was close to failure and a new engine. Being a grease monkey from my teen years, I changed the timing chain myself (saving $1500).
THIS IS THE IMPORTANT PART OF THE STORY. When I changed the parts on the 2002 Intrepid, I noticed the primary chain tensioner had blown out it's O ring and oil pressure was bypassing the normal design flow. This lead to no tension on the timing chain. It failed or was about to fail. Looking at the design of the tensioner, just a little sludge inside can cause it to fail. After changing the tensioner and timing chain, everything works great and I get very good gas milage. I do put a maintenance dose of auto Rx with every oil change, although i use 4 oz with every change. How do I know its good? I look under the left valve cover every other oil change and it's still shiny clean. This was the expensive car since it took alot of work.
After the 2002 Intrepid 2.7 timing chain change, I looked closer at the 2000 Concorde 2.7L. After the two treatments, I opened up the valve covers and still found at least 1/4 inch of sludge. Not wanting to change the timing chain, it's a real pain in the butt, I decided to try two consecutive treatrments of autorx with no rinse cycle. Afterwards, there was a significant reduction in sludge across the valves but not on the valve cover. However , I noticed the primary chain tensioner was still coated heavily in hard sludge. I decided to change the tensionioner only, a realitively minor job.The first thing I noticed was that it was frozen (it's supposed to flex) and MOST IMPORTANTLY, the O ring was missing!!!!!. After 2 auto Rx treatments after the tensioner replacement, the engine below the valve covers looks like new!!
What this tells me is that the O ring on the tensioner is CRITICAL to maintaining oil flow under the valve covers. Without it, the engine sludges excessively and eventually the tensioner will stop working and the timing chain could prematurely fail or jump. This could lead to catastrophic engine failure. Without the O ring, there is no oil pressure within the timing chain tensioner and therefore no tension on the timing chain. Oil blows by tensioner, reducing oil pressure at the top of the engine.
What causes the hydraulic tensioner to fail on the Chrysler 2.7L engines? I don't know! All I know is that the O ring blows out. (based on a randon sample of 2 engines). My local dealer tells me this design flaw has been fixed on 2004+ 2.7L engines. Even people who changed their oil every 3000 miles have reported catastrophic failures on the earlier engines. I believe them.
What if you have an earlier model? Well I would use auto Rx on every other oil change. Excessive? Only if you are willing to take off the left valve cover and inspect or change the primary tensioner. (if it's frozen, change it, a Hayes manual will tell you how).
I believe the older Chrysler 2.7L engines get excessive sludge because of the O ring failure which causes very low oil pressure at idle. Auto rx is an effective additive to counteract the problem up to a point.
Replacing that O Ring is key. Just don't replace the O ring without changing the primary tensioner. (shop for the best price).
My OCI is 3000 miles on the chrysler 2.7L, but i still use auto rx with a higher maintenance ratio on every oil change. Expensive? Yes! But cheaper than a new engine.
To inspect the O ring, you would have to remove the primary chain tensioner to do that. While I made that sound easy, the change took me about 3-4 hours and an inexperienced back-yard mechanic would take longer. You have to take off the intake manifold, remove the left valve cover, remove the tensioner cover plate, release pressure on the tensioner, remove it, inspect it, reset the tensioner (which needs a special chrysler tool to do), pry the timing chain away from the tensioner hole, insert tensioner, replace plate, release the tensioner spring and reassamble the engine. Of course you take a good chance of damaging the tensioner when you reset it, even if you had the right tool. Remember, I inserted a new one.
Now the good news..... and it won't take more than a couple of hours. Just follow the above as far as removing the left valve cover. If it's really sludged up I hypothisize that the O ring is probably gone. You can also see the primary timing chain with the left valve cover off. If the timing chain and sprocket is covered in heavy sludge you are close to engine failure based on the pictures I have seen of 2.7L dead engines.
Also you can clearly see the primary tensioner with the left valve cover off; the tensioner has an internal spring and it flexes back and forth with chain movement. I could tell that mine was frozen as it wouldn't move when I placed pressure against the chain. Also it was as black as coal and covered in a heavy tar like coating instead of shiny steel.
Another tip, the primary chain tensioner has a mark on it that indicates maximum chain wear but you can only see that without sludge. If you see that mark, then you need to replace the chain.
If you take off the valve cover and there is little sludge, just keep using autorx.
I wish there was a more simple way of inspecting these engines, but just looking under the oil fill cap doesn't work. When i bought both of these cars, both looked sludge free under the oil cap. However, if they had sludge on or under the cap, I would have bought neither of these repos. I have seen significant sludge on many used cars, regardless of make and walked away from buyng them.
Remember, some people believe in changing their oil every 30,000 miles whether it needs it or not.
I still like both of these cars, especially the Dodge Intrepid. Also from 2004 on, the 2.7L engine supposedly has been improved.
I will post some pictures of the primary tensioner soon, both good and bad.
On the internet there are a lot of horror stories about this engine.
If you have an older version of this engine, 2003 or earlier, I recommend an inspection of the valve train (take off the left valve cover). If it's sludged, use the auto rx first. Then inspect again. If it doesnt clean up after the second treatment, inspect the tensioner.
When these engines self destruct because of sludge, its due to the timing chain jumping. That can only happen if the timing chain wears a lot and if the tensioner fails, like mine did.
A warning of possible failure, is a tapping that sounds like a slapping tick. Put your hand on the tensioner cover and if you feel the slap, meaning your timing chain is not under tension. Mechanical repair is required at that time. The sooner the better.
NOW, it's my turn to ask a question of the readers here. Does anybody know why these chrysler 2.7 engines are so prone to sludging?
Please no guessing, what is the truth? Obviously Chrysler knows, because they changed the engine design.
Thanks for all that effort Steve, you seriously added to the body of knowledge here. Some things will effect how well Autorx will work at removing sludge, and obviously oil flow is one of them. Autorx can't work if it aint flowing.
"NOW, it's my turn to ask a question of the readers here. Does anybody know why these chrysler 2.7 engines are so prone to sludging?
Please no guessing, what is the truth? Obviously Chrysler knows, because they changed the engine design."
Let's get that question out in the open again. What were the design changes? What has Chrysler done to assist the owners of these older vehicles? Was there a recall or warranty extension?
