Viewing a thread - GM 6.5L diesel questions...

Forums | Classifieds (54) | Skins | Language

You are logged in as a guest. ( logon | register )

GM 6.5L diesel questions...	View previous thread :: View next thread
Forums List -> Machinery Talk	Message format

GM Guy

Posted 5/27/2019 10:37 (#7523894 - in reply to #7516731)
Subject: RE: GM 6.5L diesel questions...

NW KS/ SC ID

Any quality oil and filter will work fine, just change it often. only 7 quart system, and its IDI, so it can make dirty oil. I aim for 3-4000 mile changes on my highway rigs.

Issues: Neglect.

Neglected harmonic balancer= broke crank
Neglected oil cooler lines= locked up motor
Neglect to check fuel pressure on occasion: burnt up PMD and reduced injection pump life

Basically if you keep on top of maintenance, and DO NOT use cheap parts (autozone junk comes to mind) it will treat you well.

The PMD issue is blown out of proportion, and is fueled mostly by people that dont understand it, and try to take the cheap route on fixing it.
First, it is not moisture sensitive, and yes, you can mount it in the grille or bumper, which is where it will live a long healthy life. Second, If you put it on the firewall or fender, and its stuck under the hood with 500-900 degree exhaust manifolds, you will ruin it. potting inside is only good to about 250 IIRC.
Third, dont use cheap **** heatsinks and cables. The ebay kit is terrible. Go with the www.leroydiesel.com kit with the new PMD, put it in the bumper, and move on with life. They are not a yearly deal if done correctly. I have never had to replace one twice. PMD goes out, new Leroy Diesel kit in bumper, good to go.

On a 94, the OPS (oil pressure switch) runs the lift pump. Nice idea (safety) but not quite up to the task. Get a lift pump relay harness from www.leroydiesel.com. Makes bleeding a new filter a breeze, and lets the system run like OEM, but with a dedicated relay feeding the LP.

Harmonic damper, AC Delco OE grade off rockauto.com for budget friendly, best stock style unit. If the engine is in great shape and is worth the investment, get the Fluidampr.

Oil cooler lines, GM OE grade at the bare minimum (avoid Dorman) but preferably get the kit from Leroy or www.lubricationspecialist.com

Fuel filter, about the only ones I hear about trouble with is the cheap chinese metal cap ones. The metal cap was the original design, and if made in USA by Stanadyne, was the better filter, but the parts store chinese metal cap filters are junk. The new plastic cap filters (Wix, Baldwin, etc) that most sell do the job fine, but you gotta make sure all old gaskets are off, and dont overtighten. Do not throw away the retaining ring if you do go plastic, toss it under the seat in case you get a metal top filter on the road and need to go back to the ring securement. Leroydiesel.com sells a pre-filter, designed to let you remove the screen in the tank and do all filtering outside of the tank for easy servicing.
Lift pump: AC Delco EP158. for 92-93 .65L, flows more than the 94+, plug and play. Stock style is barely adequate though, definitely look at the aftermarket solutions on fueling that Leroy and Quadstar offer.
Run a fuel additive! unless recently major overhauled or replaced with new, the IP wont have the ULSD rated guts and needs protection for low lube ULSD. I like Stanadyne Lubricity formula.

Cooling system:
Coolant, I convert to Cat EC-1 whenever I have one apart. Which you will too if you plan to tow with it. Bare minimum needs radiator and grille removed, flush oil coolers in vehicle till you can look through them, put radiator on sawhorses, dont stop till you can look through it.

on a 94 single thermostat, I only get the thermostat Leroydiesel.com sells. Its made in Germany and makes a noticeable difference over other brands. Dont believe the internet and swap to duals, the single can block the bypass, duals cant.

If it runs hot even after a new t-stat and a deep stack cleaning, the best bang for the buck is a OE grade Delco water pump and fan clutch for a year 2000 6.5L (88894035 is the pump #) and a cooling fan from a 01 Duramax. its all bolt on. Make sure the WP is OE grade, cheaper 2000 pumps dont have the balanced flow housing change. fan is 1 inch bigger, so it might rub if motor mounts are saggy.

If its a 5 speed manual, only use the GM 12346190 fluid or the Amsoil MTG, carbon fiber synchros that dont like other types of oil.

If you want to make it a toy, a 94 is an excellent year, especially if it has the 5068 pump. Quadstar tuning could make her run hard! 94 and 95 allow for switch on the fly 6 position chips if you want to. There is turbos offered by Quad that wont light on stock fuel (aka big) and they have customers outrunning LLY Duramaxes, so they can get down OK. :)

Basically check out:
www.thetruckstop.us for support

Good parts vendors:
www.leroydiesel.com
www.quadstartuning.com
www.lubricationspecialist.com
www.PTwiringsolutions.com

I would avoid SS and A1. A1 avoid at all costs.
Heath is somewhat reputable, but there is far better for far less out there.

Good luck!

If you have any more questions, feel free to ask, or my e-mail is good. Prefer open forum so everyone can see info.

The ol 6.5Ls are definitely far from perfect, but the 400 dollar set of 8 Bosch injectors and a 1500 dollar Standyne IP looks mighty nice against the 10 grand it takes to mop up a CP4 failure on a 11+ GM or Ford. So if you dont need the power of the new ones, the personality of the ol IDI will make you happy.

I have an 06 Duramax and TBH I actually prefer to take the old 6.5L on roadtrips if I dont need the power.

Here is some of the old gals at work. Mine are stock fuel rate factory 5 speed rigs and tow surprisingly well. (white ECSB is dads and is the only automatic in the fleet, not a fan for towing. :) )
Top pic is eastbound I70 in Colorado, at the mouth of the tunnel. factory tow rating is 14,500 GCW, that pic is sitting at 21,500.
Bottom two are my beloved 95, 26,000 GCW in the top pic, miles on it on the second pic. like alot of 6.5Ls that one mysteriously got a new engine between 90-100K (warranty covered till 100K and the dealers were pretty wound up about the new 97+ crate motors with oil cooled pistons, good customers got "taken care of") so the second engine has 300K+ on it. Dont worry, dealers were not exactly right, your 94, if still the OEM 599 code engine, is actually better.

Good luck!

Edited by GM Guy 5/27/2019 10:55