Tech Tips: Porsche Boxster

For tech tips on the first-gen Boxster, we turned to Charles Navarro of LN Engineering, a Porsche specialist.

These cars handle really well. I have a stripped-down, base-model ’99 with a 360-horsepower sleeved 3.8-liter engine, and I love driving it. Boxsters are not, however, the kind of car you can just do oil changes on and forget about. 

When shopping, buy the newest, lowest-mileage example you can—but budget an extra $3000 to $5000 for some additional preventive maintenance if it hasn’t already been done. These repairs and upgrades, unlike modifications on most cars, actually increase the resale value of the car.

Engine Block Concerns

There are a number of problems with the cylinder blocks in all the Porsche engines from 1997 through 2008. The block material is very brittle. The cylinders can crack or D-chunk, which means that pieces of the cylinder walls crack and break off in D-shaped pieces. One sign of this is if it looks like there’s a milk shake in the coolant tank. The worst-case scenario is the engine hydrolocks.

Also, the Lokasil cylinder liner material wears out prematurely and can lead to badly scored bores. This will be evident by high oil consumption or poor results from a leak-down and compression test. Of the blocks we receive, it’s about 50/50 whether the bores are cracked or scored. If an engine lasts long enough, at 100,000 miles the bores will usually be out of round by 0.010 to 0.015 inch. A high-mileage car will be down on horsepower. Because of this, we liken the engine to a hand grenade with the pin pulled, but all of these problems are resolvable. A low-temperature thermostat is a good start and will prevent D-chunking. The complete solution to both problems, though, is sleeving the cylinders. We use an aluminum/Nikasil sleeve to keep the same metallurgy. 

The cooling system needs some special attention. Road debris will build up on the radiators from the back side. Remove the rear bumper and clean the rear radiator annually. 

Replace the water pump every 40,000 miles. The plastic impeller can come apart and clog up the capillaries in the head, causing hot spots. Aftermarket pumps are terrible—use only the factory piece. Use genuine Porsche pumps only.

The Intermediate Shaft

Intermediate shaft—IMS—failure is the problem you hear about most. It will fail without rhyme or reason. To spin the camshafts, the crankshaft uses a chain to spin a sprocket that drives the chains for the cams at a slower speed. Porsche engines have had this design for decades.

In these engines, a sealed ball bearing supports the shaft, unlike the plain bearing in earlier engines and in the GT3 or Turbo. When the bearing fails, the metal debris can ruin the engine. It also can allow the cam timing to jump, which will bend your valves at the very least. All Porsche engines from 1997 to 2008 have this problem—the GT3 and Turbo excepted.

Porsche does not have a part number for this bearing, and there is no specified service interval.

We worked with Flat Six Innovations to develop a ceramic hybrid bearing with a billet bearing support and flange. It’s an open bearing, so engine oil lubricates it. When buying a used car, replace the IMS bearing immediately and again every four years or 50,000 miles.

The IMS bearing design changed over the years. For the 2006-’08 models, the bearing can’t be replaced at all without taking the engine apart. These are a stronger design, but they do still fail—albeit sometimes not as catastrophically.

If you can’t bear to replace the IMS bearing right away, shorter oil change intervals in concert with a magnetic oil drain plug will let you check for metal shavings—a sign of impending IMS failure. For faster detection, we also sell a magnetic chip detector called the IMS Guardian. It will turn on a light in the dash the instant there are metal shavings in your oil.

Be vigilant, though. If you get a replacement engine from Porsche and the damage to your core return is significant, they may reject it. You could end up spending as much as $35,000.

If you have an engine failure, research the companies you’re considering to do the repair work. A quick Internet search of the company’s name will reveal their credibility.

For 2009, Porsche did away with the intermediate shaft entirely, running the camshafts directly off the crank instead. These newer engines are completely different, with no interchangeable parts. They did an awesome job on the new engine as proved by their reliability in the Cayman Interseries race cars.


A good track oil is Joe Gibbs Driven XP9, and their DT40 formulation is a good solution for the street. Change your oil more frequently than the factory two-year/24,000-mile interval. We tell people to change it every six months or 5000 miles for street driving. If it sees track use, you should really change it after every event—or, at most, every 10 hours.

Expect to need a clutch and flywheel at around 60,000 miles. The rubber isolating two sections of the dual-mass flywheel falls apart, which causes an audible clunk. Don’t be tempted by cheaper aftermarket single-mass flywheels. The flywheel doubles as the engine’s sole harmonic balancer, so use a factory Porsche replacement unit only. And whether it leaks or not, replace the engine’s rear main seal every time you take out the transaxle.

A lot of people who take these to the track will flash the computer and raise the rev limit. Do not do this. The stock rod bolts are weak, and they’ll stretch under higher revs. We see a lot of rod bolt failures because of this—they’ll either crack in half or spin a rod bearing.

If you install Hoosiers—or any tires stickier than the factory N-Spec tire—without modifying the oiling system, you’re asking for oil starvation. Don’t fit tires that have a treadwear rating of 200 or lower without modifying the oiling system in some way. A slew of options exist—baffling, deep sumps, Accusumps, you name it. How much you need depends on how much tire you have.

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View comments on the GRM forums
9/29/13 2:10 p.m.

Convinced me to cross it off of my list.

CharlieFoxtrot New Reader
8/20/14 10:14 p.m.

Amen, brother!

jj HalfDork
7/22/19 10:54 a.m.

I know this is old but are these engines really all doom and gloom like this article sounds?  

I’ve heard of spec boxster racers now getting many hours out of junkyard engines. 

penultimeta HalfDork
7/22/19 11:05 a.m.

Wow. Yeah, no thank you. 

AAZCD HalfDork
7/22/19 11:29 a.m.

There are plenty of 986 Boxsters with well over 150k miles on the original engine going strong. Two 1999s I sold were 150K miles and 175k miles with no engine problems and original IMS bearing. Currently my highest mile one is a '99 with about 145k miles and no engine issues. I have bought two salvage cars that were 2001 models over 100k miles that had a broken rod destroy the engine, but still a good IMS. Like any aging sports car; A well cared for, maintained one can last. A neglected, abused one can be a nightmare in costs.

For a good baseline on Spec Boxster engines, skim through Tom Stone's thread on the 986 Forum. I think he's on junkyard engine #5 and he runs them hard and hot. For the cost of an old 2.5L he considers them an expendable item, like tires.

Javelin MegaDork
7/22/19 11:50 a.m.

My Boxster S has 140k miles on the original engine, though it did have the IMS done as preventative maintenance when the clutch was done at 110k.

AnthonyGS Dork
7/22/19 12:32 p.m.

I’ve met Charles and Jake both.  Yes they can come across as gloom and doom, but their hearts are in the right place.  They know these engines as they have more time and experience repairing them than others.  When you see one apart and how light everything is, it’s an engineering marvel.  It’s like any other high end machine, you have to take care of it.  If you aren’t willing to do that, then you are better off in something else.

They are amazing cars to drive for sure.

A used ND Miata is probably a better choice for most though.  I dream of owning a turbo or supercharged ND myself someday.  

jj HalfDork
7/22/19 1:59 p.m.

I was thinking they weren’t so bad because of all the high mileage ones for sale. That engine thread is interesting also. I find myself in research mode again after selling my last project. 

Jordan Rimpela
Jordan Rimpela Digital Editor
9/13/19 10:25 a.m.

After driving our Boxster S project car, I'm hooked; damn the potential hazards!

bcp2011 Reader
9/13/19 11:04 a.m.

I found these quotes rather amazing (and amusing...)

"Replace the water pump every 40,000 miles. The plastic impeller can come apart and clog up the capillaries in the head, causing hot spots. Aftermarket pumps are terrible—use only the factory piece. Use genuine Porsche pumps only."

"We worked with Flat Six Innovations to develop a ceramic hybrid bearing with a billet bearing support and flange. It’s an open bearing, so engine oil lubricates it. When buying a used car, replace the IMS bearing immediately and again every four years or 50,000 miles."

And to think Porsche sold these engines for 10 years with the same design... frown

nderwater UltimaDork
9/13/19 11:12 a.m.

In reply to the above comments :

I own a 987.1 Boxster, and have driven a variety of 986, 987, 981 and 718 Boxsters and Cayman trim levels on the street and on track.  I've also owned NA and NB Miatas, and have tracked NCs and NDs. 

It's my feeling that Miatas--any generation--are the better buy for 90% of enthusiasts than a 986 or 987. Stock Porsche 981 and 718 models are a big enough step up from stock Miatas to be worth a real premium, but the Miata aftermarket is strong enough to keep modified cars competitive for most owners who aren't looking for a PDK-like shifting experience.

Hasbro SuperDork
9/13/19 9:07 p.m.

The comments are as good as the article, thanks from the Boxster newb. My 99 has 152,000 miles but I don't know much of it's history.

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