chev 6.5 diesel

Submitted: Monday, Feb 02, 2009 at 22:45
ThreadID: 65655 Views:11482 Replies:10 FollowUps:15
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Just wondering if some clever mechanical type person can give me a clue with my Chev 6.5 diesel turbo motor in a Winnebago. It has done 50,000 Klm and about to back for time number 9 to fix a rear engine seal leak. The last fix lasted all of 1000klm. It is getting fixed under warrenty but I am getting sick of taking it back. They keep telling me that there must have been a problem with the new seal that was fitted.
The question is how likely is it to get so many faulty seals?
My guess is that something else is the problem and they don't want to fix that issue. What could cause rear engine seal failures?

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Reply By: Eric Experience - Monday, Feb 02, 2009 at 23:01

Monday, Feb 02, 2009 at 23:01
A blocked breather or faulty main bearings, are the usual suspects. Eric
AnswerID: 347331

Follow Up By: Richard Kovac - Wednesday, Feb 04, 2009 at 00:39

Wednesday, Feb 04, 2009 at 00:39
hows that Eric?
no change of displacement of oil level, maybe some expansion of oil due to heat?

faulty main bearings? how will they affect the rear main seal?


FollowupID: 615650

Reply By: Member - Roachie (SA) - Monday, Feb 02, 2009 at 23:04

Monday, Feb 02, 2009 at 23:04
Neil, where are you located?

I have a 6.5 Chev donk in my Patrol and don't have that issue (it has done over 250,000klm, corrected for speedo error).

If you were located in Perth I would suggest you take it to Brunswick Diesel (they use these motors in the conversions).

In Qld it's Linquip.

In the Canberra area, there is a bloke at Hume who knows the ins and outs of these motors.

It sounds like the people you're dealing with don't know chit from clay as far as these motors are concerned.

Good luck

AnswerID: 347332

Follow Up By: Time - Tuesday, Feb 03, 2009 at 09:42

Tuesday, Feb 03, 2009 at 09:42
The Canberra "bloke" is Ritchie at Hume Off Road, 6/86 Sheppard St Hume.
FollowupID: 615529

Reply By: Top End Explorer Tours - Monday, Feb 02, 2009 at 23:10

Monday, Feb 02, 2009 at 23:10
Get a compression test, you may have dropped a cylinder, that in turn is creating blow- by and crank case pressure, this will in turn escape through the weakest link, being the rear main seal.

I hope not.

Cheers Steve.
AnswerID: 347334

Reply By: Flywest - Monday, Feb 02, 2009 at 23:18

Monday, Feb 02, 2009 at 23:18
Dead simple fix!

ALL Chev 6.5 diesels leak oil like a collander!

Theres a reason and it can be fixed.

Simply put the sump is too small a capacity (about 6 liters?) of oil for that sized diesel engine.

Comparison - my 8o - series Tdiesel cruiser is 4.2 liters and holds 10 liters oil. My 7.3 liter F 250 holds about 18 liters oil!

A 6.5 with only 6 or so liters of oil is too small a capacity of oil - it circulates about the engine so fast it doesn't get a chance to cool down sufficiently in the sump coz it doesn't stay there long enough.

In it's Parent USA with snow etc on the roads maybe a different story to Oz!

Thus here downunder the oil acts like a heat sink - getting hotter and hotter the more it circulates - until eventually the engine starts to get overheating problems when the water cooling system can no longer cope with the increasing oil temp.

Because of the excessive heat build up - the engine components expand a LOT and all the oil seals fail prematurely - which is why these things leak oil like a collander and have a litanny of overheating problems that seemingly no one can ever cure successfully despite larger radiators increased flow water pumps, balance pipes for water across the back of the heads etc etc etc

All solutions fail to address the basic issue - you need more oil capacity AND you need auxilary oil cooler radiator out the front to help cool the oil and thus the engine!.

Keep it cool and it wont get so hot that all the oil seals fail!!

An aux oil cooler - adds oil volume and cools the oil - not so hard a principle to follow

You want more oil capacity add a oil sub micron bypass filter - theres another liter or two!

As well as scrubbing you oil clean and extending the life of the engine the bypass filter gives you extra oil capacty - more chance to cool the oil - just as the aux oil cooler radiator and oil plumbing lines willl do!

I'd recon you need to aim for maybe 12 or 14 liters for that engine to do it justice and give the water cooling system in this hot Aussie climate at least half a chance to perform.

To do this you MAY have to look at modifying the sump - to include adding some "wings" like Bondys yacht keel long as they don't intefere with your front steering geometery & suspension.

This again holds more oil and allows it too cool.

You could put cooling fins onto the sump wings for extra cooling!

Combined thise suggestions will all help to fix your underlying problem.

All the other "Chev experts" will be along shortly to tell you all the other miracle fixes that don't work! ;o)

Best of luck with it - the 6.5 Chevs CAN BE a great engine that seldom reaches it's real potential in Oz due to simple lack of oil capacity!

AnswerID: 347336

Follow Up By: Member - Roachie (SA) - Monday, Feb 02, 2009 at 23:30

Monday, Feb 02, 2009 at 23:30
Give the man a cigar!!! I totally agree with everything you've said champ.

I've just removed my winch in order to have space available to fit up my Amsoil bypass filtration system with a large BE110 filter (holds 2 litres) as well as an extra "ordinary" filter in addition to the standard filter. The Patrol already has a oil cooler up there too (in front of the air con). I would love to add another 4 or 5 litres by way of a supplementry tank, but not sure how this would work in practical terms. I've looked at the sump and don't believe there is much to be gained (capacity-wise) with the wings idea; maybe a litre at most.

I haven't suffered any heating issues with mine this summer, despite record high temps here in country SA.... I must put this down to the addition of a Toyota viscous hub that replaced the piddly little Nissan unit (off the 4.2TD). It's about twice as big/heavy, so I presume it moves more air.

The oil temp never goes above about 115°C (on a really hot day only), so I think I'm doing okay.


FollowupID: 615499

Follow Up By: Member - MUZBRY(Vic) - Tuesday, Feb 03, 2009 at 09:16

Tuesday, Feb 03, 2009 at 09:16
Gday Blokes
I am sitting here at my computer, applauding the answers from yourself , Mr West and also from Mr Roach..
Many years ago , back in time when i was a little fella like little Wes, we had overheating problems with Atkinson trucks.But the engineer said they had tropical radiators. well that was his answer. I , being a smart arse young bloke said we need Australian made radiators.Almost got the sack for being rite.
The next new unit had good Aussie radiators and larger sump , never had overheating problems.
Great place to be Mt Blue Rag 27/12/2012

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FollowupID: 615524

Reply By: Member - Redbakk (WA) - Tuesday, Feb 03, 2009 at 00:12

Tuesday, Feb 03, 2009 at 00:12
What fuel figures you guys getting?
AnswerID: 347342

Follow Up By: Member - Roachie (SA) - Tuesday, Feb 03, 2009 at 08:41

Follow Up By: Neil & Pauline - Tuesday, Feb 03, 2009 at 10:41

Tuesday, Feb 03, 2009 at 10:41
I was getting between 6 and 8 klms per litre but it has now come down to 4 Klm per litre.

FollowupID: 615538

Follow Up By: Topcat (WA) - Wednesday, Feb 04, 2009 at 18:41

Wednesday, Feb 04, 2009 at 18:41
Hi Redbakk,
I have done just on 220,000km since the Chevvy 6.5 was fitted in my troopy & the best consumption I've got was 7.4km/ltr on a trip from Alice Springs to Darwin, the worst was 5.5km/ltr doing the Canning Stock Route & the mean average over that period has been around 6.3 km/ltr.
BTW my oil capacity including filter & oil cooler is 8.5 liters & I've never had any overheating or oil leak problems [touch wood]during that period. The engine was one of the first fitted by Brunswick diesels.
FollowupID: 615742

Follow Up By: Member - Roachie (SA) - Wednesday, Feb 04, 2009 at 18:58

Wednesday, Feb 04, 2009 at 18:58
I think it depends a bit on whether the Chev is turbo'd or not as to whether it overheats. Mine is naturally asphyxiated (hahaha), so doesn't have the same stresses as one that wears a hair dryer.

The thing I WOULD LIKE to do is fit a larger, more free-flowing, 4" custom snorkel. The Safari snorkel goes through too many bends and is pretty narrow compared to the plumbing under the bonnet.

FollowupID: 615744

Follow Up By: Topcat (WA) - Wednesday, Feb 04, 2009 at 19:11

Wednesday, Feb 04, 2009 at 19:11
Hi Roachie, mine is normally aspirated too. Talking about air flow restriction, when I had the Safarie Snorkel fitted on my bus just out of curiosity I had an air-flow manometer test done before & after to see what difference it made & there was very little change in the readings. Unfortunately I have lost the record of the testso can't relate what the readings were. I do remember it was a stationary one & not done while the vehicle was moving at speed.
FollowupID: 615747

Reply By: Pebble - Tuesday, Feb 03, 2009 at 10:25

Tuesday, Feb 03, 2009 at 10:25
Just expressions of interest - would anyone be interested in buying a brand new Bosh starter motor for the chev (half price?).
We've got one, never used, don't have a Chev any more and I think Hubby is still looking to get rid of it. If anyone is interested I'll list it up for sale through the trader here of course. We're in WA
AnswerID: 347368

Reply By: Neil & Pauline - Tuesday, Feb 03, 2009 at 10:56

Tuesday, Feb 03, 2009 at 10:56
Thanks for all the responses. has been very helpful.
At idle there is a vacuum at the oil filler cap. I have noticed over time my fuel economy has reduced substantially so maybe I might be getting blow past rings under load causing crankcase pressure.
Is there something on the Chev motor that will blow past and pressureise the sump when under load?

The therory on oil capacity makes a lot of sense but ours has a bit more than stated by flywest at 7.6Litres plus filter.

AnswerID: 347371

Follow Up By: Member - DOZER- Tuesday, Feb 03, 2009 at 14:38

Tuesday, Feb 03, 2009 at 14:38
Something has changed if it did not do it b4, my guess is when the turbo is boosting, there is some leaking into the sump. be it by rings or other....time to get the motor looked at under warrenty.
b4 you bag me out, walk a mile in my shoes, then your a mile away and have my shoes :)

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Follow Up By: Flywest - Tuesday, Feb 03, 2009 at 15:18

Tuesday, Feb 03, 2009 at 15:18
[quote] The therory on oil capacity makes a lot of sense but ours has a bit more than stated by flywest at 7.6Litres plus filter [/Quote]

Hi Neil,

Hopefully you can see from the examples above of:-

Lancruiser 4.2 liter TD at 10 liters oil
Ford F 250 7.3 liter T D at 18 liters oil

that probably your engine needs somewhere around 15 liters (or twice what you have now) to be able to let the oil sit in the sump long enough to cool down any!

One of the suggestions here aout having a oil temp sender in the sump and a gauge on the dash is an EXCELLENT idea - because it allows you to monitor whats happeneing inside your engine temps wise - just as a temp gauge for the water cooling system does!

The old Chev 6.5's didn't originally come with turbos, but they do seem to take them after market well enough.

Because turboeing a diesel engine aftermarket adds a LOT of extra heat to the piston crowns - you find that many diesel engines designed specifically for turboes have cooling mechanisms built into the oil system - such as oil squirters under the piston crown in top of the con rod that sprays sump oil under the piston crown, to take the heat of combustion away and into the sump oil so it can be cooled in a oil cooler radiator out front of the vehicle.

Some also have ceramic coated piston crowns to deal wth the higher combustion temps.

If the Chev 6.5 which is a naturally aspirated engine is turboed - this extra heat in the piston crown needs to be watched carefully under loads like a winnebego might experience into a headwind and on steep grades! (or if you tow anything)

For that reason I'd strongly suggest addition of a EGT (Exhaust Gas Temp) Gauge, run from a Pyrometer inserted into the exhaust pipe just after the turbo.

With engine oil temp monitored - and some extra oil capacity and oil cooling capacity with an after market oil cooler, the Exhaust gasses temps monitored - you should be able to tell - just how hot that engine and it's sump oil and the pistons crowns etc are all getting via the gauges!

I reckon your baking the rear seals and cooking them - its not the seals that are faulty it's that they are being run hotter than they are designed to cope with.

These three gauges in my F 250 monitor (from the left)

EGT (Exhaust Gas temp) - 550 C
Auto Trans Oil temp - 75 C
Turbo Boost - 15 PSI

This is as hot as I've ever had the F 250 - it was a 44 C day hauling my 4.5 tonnes of loaded boat into Exmouth over the steep Cape Range, into a 40 knot headwind!

If you had simmilar gauges added to the Winnebego - you too could "monitor" your various temps - especially the oil temp and know if you were getting it too hot and doing damage to the oil seals.

The Chevs are a much under rated engine - because so few of the after market installers that use them do anything to correct the oil shortage issue - and as a result they have an undeserved reputation for getting hot & as a result - leaking oil!

Boiling oil gets soo thin it doesnt meet its viscosity / lubricity specs and premature wear can result leading to bow bye and positive cranck case pressure issues which will only exacerbate the rear seal leaking problem.

I don't know if you have a auto tranny in that Winnebego - but if you do...

This is why I have an auto trans oil temp gauge - because excess heat from your engine will work its way thru the various metal parts of the engine etc into your trans oil and help chew up your torque converter and auto trans prematurely as well.

These are all issues here in Oz where as everyone knows it can get damn hot in our outback.

This is the crap that accumulates inside your auto tranny when it overheats and your burning the oil and wet clucthes!

I added a 3 quart larger alloy transmission pan with cooling fins & and after market transmission oil cooler radiator out front, too keep the tranny oil cool!

This is what convinced me to do such mods!

It's a used oil analysis report (on my transmission fluid) showing that the unit had been run hot and the oil report came back as "abnormal" with high wear metal contents from excessive wear and the oil badly oxidised (burnt).

Basically - you can tell if you have a sump oil overheating issue - very simply - buy buying a "Used Oil Analysis" testing kit from Westrac Equipment (Caterpillar Dealer) and having a sample of your sump oil analysed.

It will tell you firstly if your oils getting too hot and as a result it has oxidised badly - but also if you have ring wear problems leading to blow by - thru excess metal readings etc etc (Chrome for the rings).

Rather than "guessing" what your particular problem is - why not let a used oil analyisis test from Cat agent for about $50 or $70 bucks give you some factual evidence upon which to start making educated guesses!

I've told you what I reckon based on my experiences with a couple T/Diesel engines and from reading about lots of Chev 6.5 owners who alll seem to suffer the same results.

If your serious - then you'll start a process of elimination to get at the real issue!

It probably should start wth a used sump / engine oil analysis to see where you are at first, Sump Oil and EGT Gaugues and THEN start taking measures to address whatever issues you find the oil is telling you, are problems headed your way.

I'm betting it is Excess Oil temp - but heck - it COULD be somethig else - or even something simple.

At least with some empirical data you have somewhere to START looking!

When you DO get your used oil analaysis sample back - you'll need to bring yourself up to speed with what all the numbers mean, and a read of the BITOG web forums will help that learning curve process immensely - you can even post your own used engine oil results there and get advice from the forum experts - who, being US based, will be intimately familiar with the 6.5 Chev engine in all it's configurations including turboed & in winnebago's!

BITOG (Bob Is The Oil Guy) http:///

If I can assist you thru this process in a step by step logical process then I'm only too happy to do so!

You can email me if I can be of any help, getting to the bottom of your CHEV 6.5 problem!

As others have stated the people in WA down in Brunswick (Brunswick diesels) do nothing but Chev engine transplants and are a good source of info as well.

Best of luck with it.

I have no vested fiscal interest in Chev Engines - I'm just offering my advice free based on what I learned going thru a similar process.

Take it or leave it, for what it is worth.

FollowupID: 615565

Follow Up By: Member - William H (WA) - Tuesday, Feb 03, 2009 at 21:19

Tuesday, Feb 03, 2009 at 21:19
Good afternoon Neil And Pauline.

Just wondering where you are at the moment and are you in WA????????.

Cheers for now...William H....Bunbury,,,,WA.
FollowupID: 615616

Reply By: mechpete - Tuesday, Feb 03, 2009 at 18:18

Tuesday, Feb 03, 2009 at 18:18
are you sure it coming from the rear main seal ? because all the 6.5 chevs we had as ambulances ,rear main seal wasn,t a big problem . they all leak oil to a degree typical yank machinery ,
we also did not have boiling problems . unless there was a problem stick with the original chev 6.5 viscous fan hub ,in the GMC application they have an engine oil cooler as standard
we had some oil leak problems coming down from the valley under the manifold and it comes out the botom of the bell housing .tha only overheating issue we had was with the FSD on the pump would fail prematurely because of the grille lamps and driving lights and siren speakers reducing air flow .that was a long drawn out affair that pinpointed the fault after testing in a heat oven
mechpete .
AnswerID: 347408

Reply By: Ozhumvee - Tuesday, Feb 03, 2009 at 18:21

Tuesday, Feb 03, 2009 at 18:21
Check the CDR valve (shiny tin on RHS rocker cover) as it is Chev's equivalent of a PCV valve. They are a wear item and should be either pulled off, drained and washed out or replaced every 20k approx. They fill up with oil and effectively stop the intake removing crankcase pressure which could explain the blown seals.
The 6.2 (basically the same engine) in my Humvee never runs hot as it is rated for continuous duty at full load. The oil capacity is 10 litres and has an external oil filter as well as a large oil cooler approx 500x250x30mm oil filter to cool the oil.
The cooling system has a capacity of 26 litres, the radiator is 500x500x120mm 4 core and provides plenty of cooling.
The auto has its own cooler measuring 500x250x30mm and has a total capacity of 13 litres. The auto fluid is also sent through the transfer case via an intercooler to keep the fluid in the transfer at the correct operating temps.
1996 Oka Motorhome

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AnswerID: 347409

Follow Up By: Member - Roachie (SA) - Tuesday, Feb 03, 2009 at 22:26

Tuesday, Feb 03, 2009 at 22:26

Thanks for letting us (or "me" anyway....hahaha) what that item is (CDR valve). Where can I buy one of those units? (I could always phone Brunswick Diesel i guess).

I've often wondered whether it might be wise to remove it and replace it with a catch can of some description? I've had my 6.5 for over 45,000klm and have never removed/cleaned that "tin can" at all!!!

I'm also curious about your oil capacity @ 10 litres? I'm guessing this takes into account the extra filter and oil cooler. I'm hoping to add about 3 litres capacity to mine when I get the Amsoil remote bypass filtration system refitted.


FollowupID: 615630

Follow Up By: Ozhumvee - Wednesday, Feb 04, 2009 at 06:15

Wednesday, Feb 04, 2009 at 06:15
I usually buy them off ebay, do search on either CDR valve or Humvee and you can usually find them.
I would just pull it off and wash it out, just fill it with diesel, let it soak for a while and then give it a quick rinse with a bit of petrol.
Make sure it is dry with no fuel residue before refitting ;-))).
They have a diaphragm in them so do eventually play up.
The original one on my Humvee is now 21 y/o and I washed it out about six years ago and then about 3 years ago. I fitted a new one the year before last just coz I had a couple of spares.
If you ever want injection system parts (injectors, injection pumps or lines etc) get them from "Hectors Injectors" on (not ebay au), very good to deal with and cheap as. I just bought a full set of injectors, return lines, clips etc for $200 plus postage. Pumps start around $350 fully reco with new hard parts.
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Follow Up By: Member - Roachie (SA) - Wednesday, Feb 04, 2009 at 08:13

Wednesday, Feb 04, 2009 at 08:13
Thanks for that Peter....great advice. I'll take it off and wash it out this weekend.

Cheers mate

FollowupID: 615662

Reply By: RV Powerstream P/L - Tuesday, Feb 03, 2009 at 18:32

Tuesday, Feb 03, 2009 at 18:32
In Mid Coast NSW there is a little place called Failford and there is R.G. Garry Croker that has specialised in Chevy diesels for many years maintaining I believe NSW Ambulances fitted with 6.2and 6.5 Diesels.

His number is 0265543260.

Dependent on your location.
AnswerID: 347411

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