Motorhome with 6.2

[Kcustom73]

Hi all,

I haven't posted much on this site yet, but have lurked around for a few years now. I initially join the site when I started working on my 1975 Toyota Landcruiser resto/mod project. Part of this project will be to put a 6.2 I got from an 89 Vandura. I never really got to test the engine but my plan was to rebuild the thing, so all I really needed was a starting point.

I just recently purchased a 84 GMC 24' Empress Class C motorhome with a 6.2 in front of a Th400 and Dana 70 dullie axle. It has about 92K original miles on it and the PO said he averaged about 12mpg (depending on condition and load). Drove it about 100 miles from where I purchased it to garage doing the ministry of transportation certification on it and it drove well (for its size).

I just had it safetied and all it needed was front upper control arms, brake cable and rear brake servicing. Once I get it back home I want to do the following to it:

1-have new tire installed.
It currently runs 8.75R16.5 and I will change over to 16" wheels with 215/85R16. This will give me an inch of extra diameter on the tires giving a little rubber overdrive to get the RPMs down a bit. It will screw up my guages a bit but at the speeds I'll be going with this thing I am not really worried about going over the limit.

2-Change motor oil & filter
3-Change tranny oil (synthetic) & filter
4-Change diff oil to synthetic
5-Change fuel filter
6-Add tranny temp guage
7-Add EGT guage ( probe will be in one of the collector pipes right after the manifold)
Once the guage is added, I will load up the vehicle to it typical fully load state and go find myself a few hills to see what kind of numbers I get. If they are well below the 1100F max temp I have read about, I will open up the air intake and turn up the fuel screw 1/8 of a turn and see what happens. It already has a thru dual 2.25 (maybe 2.5) exhaust system. I think a little more power would help me keep my out of WOT and would improve my fuel economy just a little.

Does anyone see any flaw in my plans? Is there anything else you would do that I haven't listed (remembering that the RV runs fine right now)?

Sorry for the long post but now that I have a running 6.2, I hope to be here more often asking question and helping out if I can.

[Yukon6.2]

Hi
If you want some more overdrive you can go to a 235/85 16 tire,so long as you have the clearance for them.I have them on my dually tow truck.
Thomas

[convert2diesel]

Hi Kevin:

Have found that keeping the RPMS up on these engines does no harm and it certainly makes life easier for it in the power department. Your problem with a class "C" is not weight but rather the aerodynamics. Have successfully pulled a combined weight of 10,000 lbs (5,000 lbs vehicle weight flat towing another 5,000 lb car) with no real problems. Equate that weight into a box with all the aerodynamics of a grand piano with the lid open and your rig will need everything just to maintain highway speeds.

A good test in our area is the gradual slope on 416, going south from the Queensway to Standherd. If you can maintain 100 klics on that hill then your probably all right, at least for around here. The Gatineau hills, the Laurentians or the Adirondacs may be another story.

Bill

[Robyn]

The little 6.2 diesel is definately no MOOSE Motor but it will get the job done.

With the miles that are showing on the clock, it should be in fairly good shape still.

The first thing that tends to go away on these engines is the injectors.

If the cold start is clean and crisp without missing and blue smoke, then things are probably in great order.

Sounds like you are on the right track with your new rig.

Keep us Posted

NEEEEEEEEEEEEEEEEED PICCY'S WEEEEEEEEEEEe NEEEEEEEEED PICCY's

Missy

[Kcustom73]

Bill,

The class C sure does have the aerodynamics of a brick . I will have to try the 416 run you mentioned to try it out. I did order my EGT & tranny guage last week. Got a couple of Auburn instrument guages. We need to get together one of these and talk diesel. I still want to work on that supercharger idea we talked about a little while ago for the Landcruiser.

Missy,

Takes about 3 cycles of the glow plugs for it to start. Not sure if that is good or not. No smoke at start up from what I've seen but I've only started it twice since I'v brought it to the shop for certification. Once it get back home I will get some picks.

Thanks for all the info.

[turbonator]

hi we are located at mont tremblant quebec, if you want to talk diesel
or need any hard parts give us a pm, we are 6.2-6.5 collectors...

does your 6.2l have a j-code intake on it? if it does not it is a good indication
if the motor has been changed....

we have some crazy hills around here and we pull 12,000lbs with our 3500
with the 6.2 4l80e tranny and it gets the job done....

[Kcustom73]

turbonator,

Thank you for the offer. I might take you up on it when I start working on my Landcruiser project.

The vin number says it a J code, but haven't had a chance to take the air cleaner off to verify.

[AVM62]

I have a 1983 23' class c with the 6.2. When I got mine it had 8.00RX16.5 and I changed over to 8.75RX16.5 Cooper tires. I had no trouble finding 16.5's. I usually run at 57 mph gps which is 55 speedo with the 8.75Rx16.5 tires. I did not have a gps when I had the smaller tires. I get 10 to 11 mpg I've never seen 12. She starts first glow plug cycle when cold. I just had new windows put in. I'll post a better when I can take one. That's her in the back with her little sister.

[Kcustom73]

Finally got the motorhome back after 5 weeks at the garage. They had a hard time sourcing some of the brake cables. They also couldn't certify the propane system with the original on-board tank because of its age. So I got them to run a new line out to the back bumper and I will install a couple of 20# tanks on the rear bumper. Fabricating a new rear bumper and replacing missing main battery tie down + the above original list and she should be good to go camping in June (if the weather co operates ).

Now all I need to figure out is how to remove the inside engine cover...(help please)!

Here are some pics I took today.

[phantom309]

lift up the carpet inbetween the seats,. the dog house has two tabs with bolts into the floor,. (most van guys never reinstall them) and your two overcentre clips on either side up under the dash part,.

Nick

[AVM62]

Check to see if you have both starting batteries, when I got mine the one under the cab was missing. I only had one house battery so I added a 2nd one.

[Kcustom73]

phantom... thanks for the help. Got the cover off no problem.

AVM, I'll check for the second battery under the cab. I've got one under the hood and 2 in the coach. Seems to start fine. They did tell me they had a hard time starting it when it was parked for 4 weeks but I figured out why. The PO wired the volt meter direct to the battery so the guage is always reading voltage, so I just flip the main kill switch to off when the camper is parker. This also makes sure I don't drain my starting battery when parked.


I've got a couple of questions about non-connected wires that I noticed under the hood when I got it open

In the following pick there's a single orange wire (left side of pick) with a rubber booth that leads to nothing.

Plus in the center of the picture there is a 90deg fitting that goes to the engine that covered in oil and was wondering if this normal.



In this second pic there a pink/black & green wire going to a connector that isn't connected to anything. No idea where this goes.



Sorry for all the newbie questions but I just want to make sure this thing is safe.

[convert2diesel]

Kevin:

It would appear that you have the older style glowplug setup. Should get it changed over to the newer system. Let me know I can help.

From your first picture, it looks like someone has installed a direct reading mechanical oil pressure gauge in the truck. The wayward orange wire looks like the old oil pressure sender (idiot light) wire.

In your second picture, the plug looks like the plug for your cold start advance temperature sender (located in the head, passenger side rear). If this circuit is inoperative, that could well account for your hard starts. This plug activates the rear solinoid on your IP (the front is your fuel cutoff) that depressurizes the dome, advancing your timing by about 3 degrees until the engine hits about 130 degrees F. Its possible the PO disconnected this when the sender shorted out, keeping the pump advanced all the time. This is a common problem fixed by a new sender.

By the way, just noticed in your first post that you intend on replacing the tranny fluid with synthetic. That apparently is a no-no with the older GM trannys. Have read numerous reports of trannys dying within a couple of thousand miles afterwards. This was also seconded by my tranny guy (Len at Lentech in Richmond...high performance AOD guy). Just use good quality Dex 3 (not 5) every 30K or so. Have a spare 400 for you if this one doesn't work out.

Bill

[Kcustom73]

Hey Bill,

Thanks for all the info.

There is an aftermarket oil pressure guage in the truck. So that answer my first loose wire question. I'll just have to tie wrap it to make sure it doesn't move.

As for the second wire, I'll take a look at the area you mentioned to see if I can see the sensor. Is there a way to test the sensor to see if its working or not? If its bad and I need to replace, would you know the part number and where I could get this sensor?

As for the tranny, thanks for the info. I'll just get regular Dex3 and a new filter assembly and change that this weekend (I'll install my temp sensor while I'm at it).

Again thanks for the help.

[convert2diesel]

Kevin:

The temp sender is called either a HPCA (housing pressure cold advance) switch or a glow plug inhibit switch depending on what parts book your looking at. The unit is simply a heat activated switch that turns off at 130 degrees F. Normally when they go, they stay on. Should be around 20 bucks at any auto parts store.

On the older glow systems, this switch also prevent the glowplugs from coming on when the engine is warm. If it is disconnected, then probably the glows aren't working unless the PO hotwired the controller. If you convert to the newer controller, it can be wired to turn on the glows, regardless of engine temp. This is a good idea as any of my 6.2s are real grumpy about starting without the glows at any temp other then full operating.

Testing the switch is simple. Put a meter across the two terminals and when cold, it will read a dead short then fire up the engine and get the temps over 130F and your meter should read an open circuit.

Bill

[Kcustom73]

Not sure if this is the right place for this question, but its part of my motorhome so I guess I'll ask it here to keep everything together.

So one of the thing on my to do list was to change the tranny oil. So I get the filter and gasket from Napa and get some Dex3 Shell tranny oil from another part store and when I go to pay for it the guy behind the desk tells me I could be doing more harm then good by just changing the oil that's in the pan... He's telling me something about it might make the tranny slip??? Is there any thruth to his comments? Tranny is a TH400.

At least I've got the rear diff almost done. Pulled the cover and the oil was pretty dark. The oil in the bottom of the diff was pretty thick and black. Got the cover back on with a good bead of RTV and letting it dry at least 24 hours before dumping the new oil in it. Going to replace it with Royal Purple 75W90. Is there any issue with using this oil in a heavy duty application?

Got the old (out of date) on board propane tank removed. The thing probably weight 60-70 lbs empty.

Got my Auber EGT and tranny temp guage installed in the dash. Now I just got to install the probes. Going to install the EGT probe in the passenger side manifold just a bit ahead of where the manifold joins with the downpipe (you can sort of see it in the second picture of post #12 of this thread).

I guess that enough for tonight. Sorry for all the questions.

[convert2diesel]

Kevin:

There are sometimes that you just have to shake your head and walk away. This has to be the biggest urban myth about GM trannys. If in fact the tranny starts to slip after changing the fluid, then the only thing that was keeping the tranny together was all the junk that was floating around in it. In other words, the tranny was toast to begin with. If the tranny has lots of mileage on it, it may pay to put in some additive to freshen up the seals and tighten up the hydraulics. I have used Moly ATF for years but it is gettin harder to find (I sometimes find it in Canuk Pneau or at Home Hardware). Apperently there is better stuff out there. Try doing a search on "bobistheoilguy.com".

Tranny fluid is just specially formulated oil, designed to maintain a constant viscosity through a narrow temperature range (ergo big oil cooler). Its primary purpose is to supply a hydraulic medium to apply pressure to the various bands and clutches. It also takes a certain amount of contaminents and carries it into the filter to be screened out. As the viscosity drops (over temp) or thickens up (over age) the tranny either starts to slip (rarely) or behave in an erratic manner. As the 400 does not have a lock-up, heat is the thing that matters. Keep the fluid fresh and cool and your tranny will last for a long time.

Of all the trannys out there, the 400 is the closest to bullit proof of any automatic, regardless of manufacturer. Treat it well and it will return the favor. Just wish the 4L80 (essentially a 400 with an OD and lock-up convertor) was available without all the electronics hangin off it.

Bill

[Kcustom73]

Thanks for the info Bill.

That's what I taught also but it always better to verify with people that are actually know what they are talking. Off to go pull the pan...

[gphudgins]

nICE TO HEAR OF YOUR PLANS. I CURRENTLY OWN AN '83 ALLEGRO 23FOOT CLASS A RV WITH 6.2 GM DIESEL AND BANKS SIDEWINDER TURBO. MY BROTHER BOUGHT THIS IN '85 AND DROVE UNTIL I BOUGHT FROM HIM IN '98. 12MPG LOADED TOWING A JEEP OR SMALL SATURN. HAD ENGINE REBUILT FOR TURBO APPLICATION BY DIESEL DEPOT IN ATLANTA GEORGIA. GOOD PEOPLE THAT REALLY KNOWS THE 6.2. GOOD LUCK AND HOPE YOU ENJOY YOUR EFFORTS AS MUCH AS I HAVE MINE. phudgins25@suddenlink.net Amarillo, Texas

[Kcustom73]

Bill,

I took a picture of where I think the HPCA should be but there's another sensor there. There a wire leaving the location and going thru the firewall too... (not sure it was getting too dark to track). Can you take a look at the pic and see if the sensor I'm pointing too could be the location for the HPCA.