Heat exchanger question

This weekend, I plan on replacing my 987 heat exchanger with the larger one from the S.

Two questions, for anyone who's been there:

1. I think the exchanger can be replaced without removing the manifold. Is that correct?

2. Does anyone know the recommended tightening torque for the hex head bolts that attach the exchanger to the engine?

Thanks

I'll also replace the thermostat with a 160 degree unit and, of course, replace the coolant while I'm at it. I'm hoping my Boxster will last as long as Marc's.

Heading out on a 4 week road trip shortly - will travel down the Blue Ridge Parkway, then head over to Oklahoma, then north on the remnants of Route 66. Regrettably, because of a wedding in Canada on June 2, I'll miss BRBS by a hair.

The comments below are not mine - they are a collection I cut and pasted from PPBB. My apologies to the people who originally posted these comments/insights, as I didn't keep track of who said what.



Our cars do have an oil/water heat exchanger which serves to cool the oil when it's hot and warm it when it's cool. The oil runs through the heat exchanger just before it gets distributed through the engine.

The oil/water heat exchanger mounted to the engine block provides temperature balance. During warm-up, this system warms the oil directly from the coolant, so the engine reaches its operating temperature quickly. Whenever oil temperature exceeds the coolant temperature under high load, the heat exchanger process is reversed, with the oil dissipating heat to the coolant.

In place of the traditional external oil cooler, the Boxster engine has an oil/coolant heat exchanger. When the engine is first started, the oil is warmed by the coolant, so it more quickly reaches its proper operating temperature. Likewise, when the oil becomes hotter than the coolant - which is about 90 degrees Celsius - the oil temperature is lowered by the coolant.

Changing to a 160 stat lowers the minimum coolant circulation temp, which also lowers the normal operational temp range as well, but only by about 20F (normal operating temps in a base Boxster with the factory 180 stat, which really doesn't start to open until nearly 190 degrees, is in the 200-210 range at ambient temps of 68F, despite what the dash temp gauge says). LN engineering (and others) have also recorded much higher localized temps in the M96 engine (due to coolant flow issues), so lowering the overall coolant temps will favorably impact those localized 'hot spots' as well. In actual use, in a cold climate (regular single digit ambient temps), the car runs fine, delivers plenty of heat (owners actually comment that they get heat sooner during engine warm up, and warm up time seems unaffected), and throws no codes with the 160 stat; so the ECU is able to deal with the mixture issue; so there are not real environmental issues. State mandated 'sniffer' emissions testing have not been an issue either. PID catalogs collected in actual use tell us that cars with the 160 stat are running at 180-185 F under normal use conditions rather than the 200+ with the factory stat, so in actual usage the car is running about 20 F cooler in daily driving. So cold weather impacts have actually been positive, as have lower summer coolant temps.

As for the impact on oil, the upper viscosity range differential is actually minimal as the VI additives in the oil do not appear function in a linear response to temperature changes according to published data, so while there is some potential increase in oil viscosities due to lower coolant temps, in-use oil pressure readings have not really been observed to be conclusively higher, albeit in limited data sampling. UOA on vehicles using the lower stat have not shown any data to indicate that lowering the temp's results in higher contamination levels either, and overall the oil quality looked pretty good after long drain cycles, but again, our sample size is limited. And, as any oil manufacturer will attest, keeping oil cooler helps it do its primary jobs: heat transfer and lubrication. This is why the 'S' model had an water/oil cooler nearly twice the size of a base model, Porsche expects them to see higher oil temps and needs to shed it to the coolant and into the third radiator.

A number of reliable BTDT posts on PPBB said the S exchanger can be swapped onto the 2.7 base engine.

... Without having to remove anything else.
Make sure you purchase 4 new O-rings (2 large, 2 small).
Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Thanks Pedro.

I doubt the mounting bolts will require much tightening torgue. Maybe I'll get a feel for it when I remove them?

Interesting. I wondered how much heat these exchangers could get rid of, being located on top of the motor in a cramped engine compartment, but I guess as long as the coolant temp is lower than the oil, there will be cooling to some degree to the engine oil.

I'm probably going to do the lower temp thermo next year, along with a new water pump.



Edited 1 time(s). Last edit at 05/02/2012 09:21PM by MikenOH. (view changes)

and then can cool the oil in the heat exchanger.

I really don't know that it's necessary to do the swap. No doubt, there are plenty Boxsters that have gone many miles with the regular exchanger and thermostat.

For me, part of it is I enjoy fiddling. Though I don't want to get deep into engine internals, I like working with my hands, especially on German cars - the metal fasteners are sturdy and the parts fit well. Generally, (but not always) the design makes sense. Working on parts that haven't suffered road-salt-induced corrosion is a joy.

And, it's particularly rewarding if I can extend the reliability and life of the car.

Sometimes I'll break something while I'm working on my car. But so do 'real' mechanics. In either case, it can be fixed.

If you're paying a mechanic to do the swap, I doubt it would be prohibitive. And coolant should be changed every 3 years, I believe. So it would be a good time to do that too.