A Comprehensive Guide to Common Repairs

7.3L Powerstroke Common Repair

Words and Photos by Jacob White

We started this build in hopes of making some great content on some of the ins and outs of these old 7.3L Powerstroke trucks. The OBS Ford (1994-1997 F-250/F-350) has seen a huge rise in popularity the last year or two and their value has really increased. With that and the cost of new trucks, we find more and more guys looking to fix up an old truck, so this series of articles was designed to show off some of their strengths, point out some of the weaknesses, and suggest how to make them better.

Since this truck was bought to be somewhat of a daily driver with plans of doing some towing on occasion, all the upgrades made to it have been done to improve its ability in those areas. We added some performance tunes from Edge Products, a new 4-inch MBRP exhaust system, and fixed a few common issues like a leak oil dipstick, replacing the engine starter, and fixing some boost leaks. To keep up with the new trucks on the road, it’s still going to need some attention as the EGT’s towing gets pretty rowdy.

As many of you Ford faithful already know, the 1994-1997 7.3L Powerstroke was never equipped with an intercooler. Ford just opted to go with a really large 1.15 a/r exhaust housing on the stock turbocharger to help combat high EGTs. However, even in a bone stock application that left something to be desired. That stock turbo is a bit laggy with the 1.15 a/r, and EGTs are still tough to manage while towing long grades, especially with added power. A tighter exhaust housing could be installed to help with the lag, but that will just compound the EGT problems by increasing drive pressure and restricting exhaust flow. Cooling the intake charge and increasing the air density making its way into the cylinders is the most effective way to make the improvements we’ll really see benefits from.

While the turbocharger is used to compress the air and get more air volume into the engine, compressing it also heats the air, making it less efficient. An intercooler is used to remove that heat, but it needs to do it without blocking airflow to your radiator, so you aren’t dealing with overheating. With a few intercooler kits on the market, the guys at Obsession Diesel and OBS Solutions put their heads together to create a better fitting and more functional kit. Dan Howard of Obsession Diesel has been in the game a long time and wanted to develop an intercooler kit that would give owners room to grow and change as their build progressed. With his fabrication skills, paired with the knowledge of the OBS platform from the crew at OBS Solutions, they put together this combo that fits like an OEM unit would’ve and solves a couple other issues while you’re at it.

The installation of an intercooler kit in these older Ford trucks can be rather labor intensive, but thanks to their forethought, it’s really as simple as following their steps and watching their YouTube installation video. OBS Solutions developed the intercooler mounting bracket kit that locates a stock 1999-2003 7.3L intercooler or their aftermarket Icebox unit right behind the grille without interfering with a bunch of other stuff. The new intercooler will literally fit like it would’ve from Ford. Everything bolts together easily, but there is need to cut the core support for the charge air pipes to pass through. This system was so well thought out, however, that just going one step at a time had this whole process done in just a few hours. One of the other issues this kit works through is the transmission cooler on automatic applications. The stock cooler is tiny, and transmission temps while towing are always an issue. So that mounting bracket kit allows you to install the massive 2003-2007 6.0L Powerstroke transmission cooler behind the intercooler and in front of your radiator. On our truck, we used a Mishimoto replacement transmission cooler, and it worked out perfectly. Most of your time working on this installation will be spent removing the factory front clip, like the grille, headlights, and header panel. OBS Solutions kit goes together extremely well, and when paired with the stainless steel TIG-welded pipes from Obsession Diesel and the CSF replacement intercooler we used, you’ll come to appreciate the quality of planning of it all.

As we mentioned before, Obsession wanted this to be a kit that could grow with time, so while in this application we’re still running a factory style turbocharger, the piping is somewhat universal and will allow you to upgrade to a much larger S300 or S400 based turbocharger should you ever decide to with just the addition of their T4 mounting pieces. It’s all modular and can be mixed and matched to create the perfect turbo and cooling combination for your fueling upgrades. So, when it comes time to install some Stage 2 or 3 injectors, we can turn to Obsession for a S364, S366 or even a big old S467 to get the airflow we need without starting over from scratch.

Results

First off, we’ll start here by stating these results were strong enough for us to suggest the intercooler installation being your first priority as a ’94-’97 7.3L owner. If you plan to do nothing else with your OBS Ford, plan on doing an Intercooler kit, the drop in EGT’s and increase in usable powerband is that impressive. Before installing the intercooler kit, we made some data logs on our Edge Insight CTS3. Some at wide open throttle unloaded and some while towing a 10,400-pound fifth wheel trailer over a long torturous 6% grade just outside of Salt Lake City.

For the wide-open throttle runs before the intercooler install, our numbers showed 28-psi boost, 1633-degree’s peak EGT, and 339-degree charge air temps at the cylinder inlet. Making the same run after the intercooler was installed, we’re seeing 24.6-psi boost, 1365-degree’s peak EGT, and just 106-degree charge air temps. That should be all the data you need to see the importance of intercooling, but towing is where it really earns your respect.

The grade we tested on has been known to kill many trucks in the hot summer months and maintaining the 65mph speed limit is tough on even brand-new trucks while towing heavy. Forgetting about the speed limit and focusing on nothing but the EGT gauge, it was virtually impossible to stay under our 1350-degree safe zone. We ran the last two miles of the grade in 2nd gear at just 37mph. Contemplating reaching for the hazards and asking my wife to jump out and help push, we finally crested the top with the engine oil and coolant about ready to boil itself out of the engine.

Three weeks later, with the new intercooler kit and bigger transmission cooler installed, we towed the same trailer over the same grade. The only real variable was the outside temp, which was actually 10 degrees warmer on the second test. Conditions were worse, but the results were far better. With the charged air coming out of the turbo being cooled through the CSF intercooler core, we had so much more throttle to play with. This trip, we were able to pull 3rd gear the entire grade at 59mph and never went past 1250 degrees. We gained over 20mph and still kept it 100 degrees cooler. Towing the same load over the same grade 20mph faster is incredible, especially when you consider we didn’t really add more power, just accessed power we had but couldn’t use before. By maintaining a more constant throttle input, RPMs were easier to hold, which kept boost where it needed to be, and our engine oil and coolant temperatures were kept a little more under control as well. That big old transmission cooler helped substantially as well.

While the intercooler does take some investment in both your time and money, if you plan to increase horsepower in a 1994-1997 7.3L Powerstroke and have any intentions of towing, it’s worth every penny and bead of sweat invested into the job.

SOURCES

Obsession Diesel
www.obsessiondieselperformance.com

OBS Solutions
www.obssolutions.net

Mishimoto
www.mishimoto.com

Complete Performance
www.cpaddict.com