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Hello From SoCal

Big T

Big T

Well-Known Member
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Location
Fullerton, CA
Steve here from Fullerton, CA. Have owned a 1995 GMC 2500 Suburban 4x4 w/ 6.5TD since 1998. Been through all the issues and was a member of Jim's DieselPage for awhile. Truck is basically stock save for Banks 3" down pipe and 4" catback and the upgrade water pump and dual T-stats. 156K miles on it, lots of it towing boats. Have a 20' Blackman center console with Volve AQAD31A diesel and DP 290 drive for saltwater fishing and a Ranger 198 Bass Boat with Yamaha F115 four stroke for freshwater fishing. I do all types of fishing from marlin on the salt to dry fly fishing for trout on the streams.

Originally bought this truck to be able to tow my Blackman down the Baja to fish the blue marlin at the East Cape in August. I soon realized that the engine would not be able to withstand the heat of a Baja summer while pulling a 6,000 lb boat up a steep grade. So I turned to the web to find solutions. The basic mods I've done have really cooled the engine down, but still feel there is more I can do. Just never bit the bullet for an intercooler as I do like to take this truck off road. I have yet to tow the Blackman down to the East Cape. Something about raising a teenager, remodeling home, career, etc. getting in the way. Very interested in the ATT Turbo solution. I regularly take this truck up mountains as we have a place on Big Bear Lake (6,750'). Towing the bass boat up there is an interesting experience watching the gauges. Probably something I would not do during the heat of summer.

Love sites like this where I can obtain good info from crazy gear heads who love working on their trucks.

Steve
 
Hi Steve... welcome to the site!

Cooling is indeed an issue with these trucks, especially when towing at altitude or in high ambients, but one most of us have managed to conquer.

I note that you call your truck mostly stock... can you please take a few minutes to quantify that, by filling out your signature and listing what your mods and specs are? That way, we don't have to keep going back to post #1 to check, or guess.

< I suck at guessing>

We can almost definitely help you make it pull hard, high, and cool... as was mentioned, there is nowhere else to find 6.5 heads like this place has!

Jim
 
JiFaire said:
Hi Steve... welcome to the site!

Cooling is indeed an issue with these trucks, especially when towing at altitude or in high ambients, but one most of us have managed to conquer.

I note that you call your truck mostly stock... can you please take a few minutes to quantify that, by filling out your signature and listing what your mods and specs are? That way, we don't have to keep going back to post #1 to check, or guess.

< I suck at guessing>

We can almost definitely help you make it pull hard, high, and cool... as was mentioned, there is nowhere else to find 6.5 heads like this place has!

Jim
Click to expand...

Jim, I did the click here in your post to add my signature data, but it's not taking.

Steve
 
Steve, what kind of boost are you running when pulling at altitude (when it starts to overheat)? I ask because I had those issues before changing some stuff - pulling a 9800lb 5er uphill at 30mph - big time overheating problems.
 
Jim, at sea level it hits 7 psi, 5 to 6 sustained. Up at 5000' to 7000' it will hit 9 psi, 7 sustained. The highest temp I've seen was recently (before replacing the wastegate solenoid) when I banged it up a 4wd road, boulder hopping along the way, reaching 9,500'. I was a slow grind, probably should have had it in 4Lo, but didn't want to touch that once I was in it and going for it. Coolant temp hit 235 F at the top. I left it running with the hood up to breath in that fresh cool air while the wife and I did her geocache thing and took in the views. Signed the log at top of the peak and noted someone's comments that their Jeep overheated. It was not an easy climb, with wheels taking air and grabbing and shooting boulders when they came down. But it was fun.

Most of the time up the mountain towing it will hit 220 F. I try to keep the EGT below 1200 and that's taken before the turbo at the connection of the crossover to the exhaust manifold.

I've longed to add an aftercooler, but they're pricey. Now it seems like the ATT guys are pushing away from that.

Steve
 
OK, there's part of the issue. There are likely others.

When mine was overheating, I had a few things going on that all needed to be addressed... good cooling is a matter of a lot of little things adding up, more than one big thing fixing the problem. Here's a list of things to consider:

1: Rad and coolers must be clean. Spotless. I washed it out with a pressure-washer while it was still in the truck, and still overheated. So I took the rad completely out of the truck, set it face-down over some sawhorses in the driveway, and washed the fins out with some degreaser/foaming cleaner and a garden hose ... 3 times. I was AMAZED at what came out; bugs, sand, poplar fluff, slow hitch-hikers, a Prius... made a hell of a mess in my driveway. I had what looked like a wool blanket (fuzzy crap) between my rad and the AC condenser, too. Spotlessly clean.

2. The fan clutch HAS to kick in early enough to matter. There is a thread on here about cleaning the clutch, even one about tweaking the engagement temp, both of which help. BUT - the thing kicks in based on AIR temp, not water temp... you have to be moving fast enough, with a clean enough rad, for air to be coming through, heating up, and activating the clutch. See step #1 (above). If neccesary, you might need a new fan clutch. If you can't hear yours kicking in, and if it doesn't kick in early enough, ask about that.

3. IATs and EGTs - there is a subtle balance here... if you compress intake air too much, it heats up (needing intercooler)... if you don't get enough air IN, then your EGTs go crazy. Either will heat up your engine. More boost is always better, up to a point. Mine pulls uphill with about 12-14 steady with a big load on. When it only had 5-7, I had issues both with power and overheating. Getting more air is important. An ATT will definitely help this equation, but so will a turbomaster on your existing GM-4. A chip will also affect this, if you decide to stay with the vacuum-controlled system.

4. - Transmission TCC lock - an unlocked tranny will develop more torque, helping you pull, but it also generates a lot of heat, that gets dumped into your rad, causing water overheat issues. You have a '95, with an OBD-I... consider doing a TCC Lock Mod to use when pulling your boat.

5. - Speed. Airflow = cooling. When you can't keep your speed up, your ability to cool goes down. You might want to consider a chip to up your pulling HP and manage your shift points. Places where I was 25 mph and overheating before I did these things, I was 55 mph and 195* after doing them.

All things considered, making these changes completely changed my truck.

If you're interested in all or any of them, the guys on here can help. My recommendation is to AT LEAST do the cheap (or free) stuff.. clean rad, clean or adjust fan clutch, TCC lock mod, and add a helper spring to your wastegate arm (to see if more boost helps keep you cool when pulling uphill; this is NOT a 'fix', just a way to gather more data to see if you NEED to fix.)

Jim
 
Jim, my answers are below, point-by-point:

JiFaire said:
OK, there's part of the issue. There are likely others.

When mine was overheating, I had a few things going on that all needed to be addressed... good cooling is a matter of a lot of little things adding up, more than one big thing fixing the problem. Here's a list of things to consider:

I'm going through this right now on my diesel in the saltwater boat. Going through the entire cooling system as the temp at cruise speed was at the upper end of the specified range. Lot of little things like pieces of kelp in the intercooler, some scale in the heat exchanger etc.

1: Rad and coolers must be clean. Spotless. I washed it out with a pressure-washer while it was still in the truck, and still overheated. So I took the rad completely out of the truck, set it face-down over some sawhorses in the driveway, and washed the fins out with some degreaser/foaming cleaner and a garden hose ... 3 times. I was AMAZED at what came out; bugs, sand, poplar fluff, slow hitch-hikers, a Prius... made a hell of a mess in my driveway. I had what looked like a wool blanket (fuzzy crap) between my rad and the AC condenser, too. Spotlessly clean.

I just did the rad with a pressure washer in the truck. As I'm having a slight coolant leak from the water pump, I'll pull the rad then and do the full clean job.

2. The fan clutch HAS to kick in early enough to matter. There is a thread on here about cleaning the clutch, even one about tweaking the engagement temp, both of which help. BUT - the thing kicks in based on AIR temp, not water temp... you have to be moving fast enough, with a clean enough rad, for air to be coming through, heating up, and activating the clutch. See step #1 (above). If neccesary, you might need a new fan clutch. If you can't hear yours kicking in, and if it doesn't kick in early enough, ask about that.

Mine's kicking in. It was running at the top of that peak climb and that was a crawl up it. I realized that it was working hard and not getting enough air flow.

3. IATs and EGTs - there is a subtle balance here... if you compress intake air too much, it heats up (needing intercooler)... if you don't get enough air IN, then your EGTs go crazy. Either will heat up your engine. More boost is always better, up to a point. Mine pulls uphill with about 12-14 steady with a big load on. When it only had 5-7, I had issues both with power and overheating. Getting more air is important. An ATT will definitely help this equation, but so will a turbomaster on your existing GM-4. A chip will also affect this, if you decide to stay with the vacuum-controlled system.

The subtle balance thing is understood. That's why I have the gauges. Not familiar with a turbomaster, but have read most of the threads on the ATT. If I went the ATT route, do I need to chip it with something like the Heath GL4? What about an aftercooler with the ATT? I don't see much talk about any benefit from an aftercooler with the ATT, but Jim Bigley big on one with the the GM-4.

4. - Transmission TCC lock - an unlocked tranny will develop more torque, helping you pull, but it also generates a lot of heat, that gets dumped into your rad, causing water overheat issues. You have a '95, with an OBD-I... consider doing a TCC Lock Mod to use when pulling your boat.

Now this is completely unfamiliar territory for me.

5. - Speed. Airflow = cooling. When you can't keep your speed up, your ability to cool goes down. You might want to consider a chip to up your pulling HP and manage your shift points. Places where I was 25 mph and overheating before I did these things, I was 55 mph and 195* after doing them.

Understood. That's why it got hot doing the mountain climb. I'd like to be doing the 55 mph and 195 thing.

All things considered, making these changes completely changed my truck.

If you're interested in all or any of them, the guys on here can help. My recommendation is to AT LEAST do the cheap (or free) stuff.. clean rad, clean or adjust fan clutch, TCC lock mod, and add a helper spring to your wastegate arm (to see if more boost helps keep you cool when pulling uphill; this is NOT a 'fix', just a way to gather more data to see if you NEED to fix.)

Just wrapping up the saltwater fishing season here, then I will do these mods in the offseason....err winter if you can call it that here:smile5: I may do a road trip shortly to Idaho/Montanna to get in some fall fly fishing, but I need to address the coolant leak first and do the rad and other coolers at the same time.

Jim
Click to expand...
 
Welcome to DTR Steve!
I was gonna say make yourself at home, but I see you already did...):h
 
Thanks for the warm welcome from all of you.

I really knew very little about diesels when I bought this Suburban back in '98. When I first started having issues, I started reading up on the 6.5 TD on the net. My heart sunk as I came to believe that I had bought a truck with a lemon engine. I methodically started addressing the issues and it became a fairly decent truck to tow my boats, go off roading, and take camping/fishing trips in. I've had this Suburban (and the wife) all the way to Galbraith Lake, which is on the Northern side of Atigun Pass in the Brooks Range, or for most the North Slope of Alaska. 11 years of ownership and 120K miles while I've had it and the 6.5 TD issues now seem trivial. Still, I know I can get more out of this engine and it seems as though others have really started to dial them in.

I'm due to address this slight coolant leak around the water pump. While in there I will clean the rads, new timing chain and also considering new injectors (these are originals). Once there's more data on the ATT (i.e. true Torque and HP curves) with various chips, then I'll be ready to make that move. One of the first things I did when finding this site was to buy the dash rattle stops. I guess I'm not alone with these issues.

Again, thanks for the welcome.

Steve
 
Big T said:
Thanks for the warm welcome from all of you.

I really knew very little about diesels when I bought this Suburban back in '98. When I first started having issues, I started reading up on the 6.5 TD on the net. My heart sunk as I came to believe that I had bought a truck with a lemon engine. I methodically started addressing the issues and it became a fairly decent truck to tow my boats, go off roading, and take camping/fishing trips in. I've had this Suburban (and the wife) all the way to Galbraith Lake, which is on the Northern side of Atigun Pass in the Brooks Range, or for most the North Slope of Alaska. 11 years of ownership and 120K miles while I've had it and the 6.5 TD issues now seem trivial. Still, I know I can get more out of this engine and it seems as though others have really started to dial them in.

I'm due to address this slight coolant leak around the water pump. While in there I will clean the rads, new timing chain and also considering new injectors (these are originals). Once there's more data on the ATT (i.e. true Torque and HP curves) with various chips, then I'll be ready to make that move. One of the first things I did when finding this site was to buy the dash rattle stops. I guess I'm not alone with these issues.

Again, thanks for the welcome.

Steve
Click to expand...

Thank you for your business!
 
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