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General Discussions about the 300M and other LHs

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 #395112  by 135sohc
Many years ago I was on LH forums and I see that is no longer around. so here it goes.

Last monday (presidents day) I had the day off and was going to change the battery and put a new piece of pig mat on the transmission "drip tray" (more on that later) and long story short I managed to drop the car on the radiator cross member.

killed the radiator, condenser has another kink and twist added to it, broke the passenger side head light. I straightened out the cross member and actually found a NOS one on ebay the same day and got it anyways.

The DEPO brand headlights at first glance appear OK. I am going to fix the broken tab and put the OEM units on the shelf for spares when I get the time. They need a full sand and re-polish anyways.

Tearing down the front end to fix all the damage I inflicted. The timing belt is due anyways and more on my transmission 'drip tray' I mentioned above. In November of 2019 I swapped/installed a transmission that I had built a few months earlier (I spared no expense on that transmission) to replace the original one that was developing a steady drip @ the torque converter pump seal. By march of 2020 as C-19 was closing in and my new transmission started dripping I hastily cut and bent up a bracket that bolts underneath the structural collar just above the sway bar to hold a piece of rolled up pig mat.

Whether I botched the install and damaged the pump seal, the reman TC has a faulty weld or the transmission is leaking in the bell housing somewhere. I don't know yet and hopefully tomorrow I will have the engine/transmission plucked out and share the findings. I have another reman TC here to install along with changing the seal and putting in a new pump bushing. If it still leaks after this I will give up and make a full underbelly drip tray to funnel the atf into a drip can.

While the engine is out I will be resealing the entire bottom end and installing a new oil pump. Also doing the 2005+ rear main seal retainer. Not exactly happy about that but with the engine on the stand and flipped over and doing all three sealing surfaces in one hit I hope to eliminate the seepage that has come around the entire bottom of the engine.

As well I pulled the timing cover off to reseal as it has never been off and was seeping on all three O-rings. I already had the cam sprocket stretch bolts in stock from 2019 as I was prepared to go in this far but never did.

Couple things to share here since starting 'round 2'.

The two smaller O-rings on the back of the timing cover that seal it to the block (mopar 4483443) are an industry standard '#219' and big o-ring (mopar 4659430AB) is a '#240' o-ring. I refuse to pay $60+ for three o-rings from chrysler. and I fully expect whatever shows up in the gasket package will be the cheapest round profile crap that could be sourced. What remained of the originals appeared to be a square profile so I opted for some square profile silicone o-rings from Mcmaster. Both the block and timing cover sealing surfaces were slightly pitted so they will be going back together with a thin layer of rtv plus the o-rings and hoping for the best..
The camshaft thrust plates use a #136 o-ring.

Past discussion of the 3.5 water pump has always been to suck it up and only buy the OEM pump. Is that still the best way forward ? I have both a Bosch (made in china) and FVP which says Thailand on the box.
Given the important function of the 3.5 water pump cost is not a concern, assuming chrysler is not simply re-boxing an offshore sourced unit.

more to come. that was a lot of rambling for a first post.
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 #395116  by FIREM
Some folks believe that OEM is the only way to go.
Evidence reported here is a factor in any replacement pump.
Personally use Carquest pump with lifetime warranty as I do all my own work. Not that it will last a lifetime, I just don’t pay for replacements when needed.
Be sure to use Coolant Rated RTV on those seals.
 #395117  by cin993
Good info on those oring sizes. Been about 8 years since i changed mine; and i also had slight pitting on the block so used little JB Weld to fill the pitts

Where you located, what state?

On my first timing belt/water pump service i used a complete AC Delco kit which included a Gates version water pump with the grey plastic impeller. This wp was similar to the original one in there which at about 10 years wasn't even leaking and the bearing seemed fine.
After less than 5 years and only about 50k miles this second water pump developed a leak. Was not exactly happy with the quality

I used an OEM chrysler water pump as a replacement; it has the metal impeller.

Where do you believe your oil seepage is from? Front crack seal? or generally the oil pan gasket?
 #395123  by 135sohc
I am south of DC in Southern Maryland.

The original pump and all pumps that have been on this engine had the white plastic impeller. I have never seen a pre 2005 style pump with a metal impeller. There will be more nickel and dime stuff to order this week so I will attempt to order the whatever Mopar pump is available and see what I get.

About a year ago I replaced the oil pan gasket as it was seeping along both rails. That did not fix anything and it only got worse plus the transmission leak. The actual front crank seal I believe was never leaking and the same for the rear main seal. I got the engine & transmission pulled today and stripping the oil pump and rear seal retainer off the block. The sealing beads on the rear retainer were flattened and rock hard, the sealing beads on the metal shim gasket behind the oil pump were rock hard as well. 21 years and 330,000+ miles I am not upset or surprised to see that.

Removing the torque converter the only thing I can say for sure is the TC was not the leak. With the entire inside the bell-housing being wet and dirty I cannot for sure see where the leaking was occurring. I'll do the TC/pump seal, a new bushing, new pump to case seal and o-ring and put some RTV on the pump bolts.
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 #395124  by M-Pressive

You can get an oem pump with a metal impeller.


Not sure where you order from but I have good luck with Steve white parts.

Face1 for an extra bit off the order.

Don’t forget the oem gasket as well.

 #395130  by 135sohc
That is the pump I have used before, but it was the 'value line' V9900085 part number last time, which I see was superseded again to that number. Got one coming.

To add this in here, the engine oil dipstick tube O-ring a metric 2mm wide, 6mm ID, 10mm OD seems to be a good fit. Still need to figure out the transmission dipstick tube and the oil pickup tube o-rings. I ordered the chrysler part numbers as they were cheap enough and not paying extra shipping so I can have good known samples to work with and get a good mcmaster part number.
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 #395133  by MoPar~Guy
I've only replaced the water pumps in my 300m's when I'm doing a timing belt replacement. I've done 3 belt replacements so far. For those 3 I've used the Dayco kit WP295K2A that includes the water pump. I've bought a gates kit TCKWP295C a few months ago for when I do my next M. These kits tend to cost $140 - $150 USD. I've never had a water pump leak. I would venture to say that these are not complicated pumps and don't push any engineering or technology limits so it's not going to be hard for anyone to make a durable/reliable pump. I've saved all the original pumps (they were factory original) and I could be wrong but I don't think any of the original or replacement pumps had metal impellers, and I've never seen a hint of damage or wear on the old impellers.

I make sure the mating surface is shiny clean before putting in the new pump, I spread some silicone grease on the O-ring but do nothing else (no sealant).

On 2 of my M's I've put in 170F thermostats (instead of 180f) and I'm happy with how that's been working, keeping the head temps consistently closer to 190. The engine temp regulation is horrible on the 3.5L because of where the thermostat is located - on the coolant in-flow cold side instead of regulating the head temperature on the hot outflow side. Chrysler knew this - they designed the needle response on the temp gauge to have a dead band area that doesn't respond when the head temp fluctuates between 195 - 210 area.
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 #395139  by LUNAT1C
In my admittedly limited experience, I would agree with Bob that the pump-to-housing seal is the more typical culprit of water pump issues. My original was leaking from the pump shaft slightly at 82,000 miles and 8 years of service. Gates replacement went in and after 7 years (maybe 40-45k miles? I don't have my log book next to me...) it was leaking from that sealing area. Replaced with a Carquest. 2022, since I didn't trust aftermarket pumps to last more than 5 years, I went back in and replaced the timing set again. Pump was barely leaking from that same seal.

This time around I cleaned up the sealing surface with scotchbrite pads and got it nice and smooth, and replaced with a NOS OEM pump with the original white impeller, from 2006, and new OEM seal. I ordered a new OEM seal, did not use the 2006 seal that was in the box (just in case).

We'll see how it is in 2029. I may also pull the timing housing at that time and preventatively replace the rear seals.

Unfortunately I believe the newest Mopar branded pumps are still not the original pump design, I have yet to see the white plastic impeller on anything since the originals were discontinued. Just metal impellers. Again, I'm not convinced that's necessarily the issue and using the OEM "ribbed" (for lack of a better term...) gasket is the way to go, while ensuring a good sealing surface with the housing.
 #395142  by 135sohc
MoPar~Guy wrote: February 26th, 2024, 9:09 pm I would venture to say that these are not complicated pumps and don't push any engineering or technology limits so it's not going to be hard for anyone to make a durable/reliable pump.
Coming from the 2.2 4 cylinder background. The water pump on second gen 3.5 has a lot more 'responsibility' and if it decided to stop working with little to no warning the damage could be the end of your engine. Kinda why I don't trust the aftermarket, they can, will and do cut corners at every chance given. 2.2 pumps are about $25 now and unless you find NOS when the aftermarket still sourced them from Mexico they are all coming from China now. Very high failure rate, I keep an extra pump & housing assembly built up with a timing belt and tensioner on the shelf for my 2.2 rig. Every 18-24 months like clockwork the pump starts dripping and the squealing starts soon after.
 #395144  by 135sohc
Pump came in, cast iron impeller. It was packaged at the end of 2021. Assembled in US with foreign parts... The timing cover was reinstalled with rtv to supplement the o-rings. I used an AISIN branded rtv that I will say just blows away anything from permatex. It is hard to describe other than it just comes out of the tube smoother and spreads out nicer. Rated for coolant and oil exposure.

I ordered the Victor-Reinz exhaust manifold gaskets based on the picture from rockauto and what was received was nothing like the oem type embossed steel shim gasket. They look similar to the Ultra-power or Apex branded gaskets. Perforated steel over a graphite core, garbage waiting to blow out.

Ordered with the pump I got two Mopar exhaust manifold gaskets. Manifold and head sealing surfaces cleaned up respectably for an engine with 330,000 miles. A generous application of head gasket magic in a can (copper spray-a-gasket) was given to both the manifold and head along with the gaskets. ARP stainless studs were used to hang the manifolds back on. 400-8015 & 400-8005 for a total of 12 fasteners

Using the later 2005+ rear main seal, gave it a big fat bead of rtv across the bottom lip and fingers crossed it will seal. I had a couple leftover ARP accessory studs from my last 2.2 build, they were too short for the 3.5 exhaust manifolds but perfect for the oil pan by putting one in each corner where the M8 sized fasteners go it supplements the two studs on the front in the oil pump housing. Doing the rtv, putting on the gasket and then dropping the pan on. The gasket alignment stays dead-on and all the remaining bolts drop right into place.

I ran into snag putting the timing belt crank sprocket back on tonight. I have the Miller 6792 for pressing the harmonic balancer/crank pulley back on to the correct depth but not the 6641.

Does anyone know either how deep the 6641 press tool is or have an accurate known distance from the end of the crank snout to the face of the sprocket ?. In my mind I had the 6641 tool and thought nothing of it as I was pulling the sprocket off otherwise I would have measured the depth before disturbing it.
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 #395158  by 135sohc
DHL + USPS what could go wrong..

Got the whole works on hold waiting on the pump to case paper gasket and the pump o-ring circumference seal. Supposed to deliver last wednesday, rock will not touch it until day 9 of being 'late'. Ordered from transmission parts usa this time, had to plus up the order just to justify the shipping.

The front end light wiring was gone through and the grounding circuit was upgraded. Shame on Chrysler for that one, the two radiator fans are there own grounding circuit. All of the lights, washer pump, horns are tied together and grounded to the car with a single 16 gauge wire.
 #395186  by 135sohc
Got the engine & transmission mated together and dropped back in Sunday. My little tractor was not liking it but it did alright.
Could not make a positive confirmation but I believe the source of the transmission leak was the pump bolts. New pump bushing and seal were installed new gasket and sealing ring installed and the bolts were given a healthy bead of RTV under each bolt head and run back in.

The ps hose from the reservoir to the pump I had to fabricate a new one using some brass 90* elbows and petroleum rated hose. That hose is not available from Chrysler and the aftermarket does not offer one either.

One of the hiccups from 2019 during the installation of the flexplate to TC bolts was the discovery that one bolt hole was off by 1/4 inch. Not wanting to repeat this I checked the new TC against the NOS flex plate I was intending to use this time and found all the bolt holes matched up like they should. More research shows that I received the wrong TC in 2019 and the one I got was for a first gen LH where one bolt hole is offset. When I send the old converter back for core credit I hope they don't notice that..
 #395219  by 135sohc
Got it running Saturday 3/16/24. No leaks yet, maybe it will stay that way this time.
Much nicer than driving the truck every day.

One more thing to do this afternoon, thinking I might have a solution for the starter solenoid connection. Mine was crusty and not aging well.
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 #395226  by 135sohc
One more thing and I'll be done here.

Yazaki CN-A Locking Type - 250 Connectors- part number YC2501 and its matching terminal are a direct fit for the 3.5 starter motor solenoid connection. Mine was crunchy and needed to be replaced. Awhile back I did so using a common spade terminal and stuffed it in there. I like having the proper locking connection though. Less likely to come unplugged and leave you stuck with no starter.

3.5 (and 3.3!) starter for all years--> ... 52&jsn=885
2.7 starter for comparison, it uses an open spade terminal--> ... 52&jsn=931
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