Yamae

It depends on the Arrhenius equation and you can calculate the expected life span in accordance with the capacitor's spec. Simply to say, the life of aluminum electrolytic capacitor is temperature dependant and it is doubled when ambient temperature is 10°C lower. If 30°C lower, 8 times longer life.

For examples, if the spec says 3,000 hours / 105°C, and your operating temperature is 45°C, you can expect 192,000 hours. ie 3,000 x (2x2x2x2x2x2) = 192,000.
If your operating temperature is 25°C, you can expect 768,000 hours. ie 3,000 x (2x2x2x2x2x2x2x2) = 768,000.

On the other hand, QAS capacitors don't follow the Arrhenius equation well. The shortest life span I have experienced was 12 years here in Japan. We have warmer summer compared with Singapore though but we also have cold winter.

The link below may help you more to understand about the life.
http://www.rubycon.co.jp/en/products/alumi/pdf/Life.pdf

KA8

iTrader: (1)

Well, I had some symptoms mentioned on this thread so I opened mine and 3 of them totally leaked out. So I replaced the caps but symptoms remain. Looks like when you're getting symptoms you may have damaged something else. I took a chance with ECU rebuild on ebay. Just got it back and so far very happy with it. If new caps don't solve your issues give rebuild a try. Cost me $65. I thought it sounds too good to be true but at $65 why not. Plus if it can't be repaired I'll get my refund. Also comes with 3 yr warranty. I'll have to drive it for a week or so to be sure but issues so far.

outdone

My 92 c400 wasn't really running that good and yet sometimes it would run fine. Then it started shutting off while driving...Yikes! This led me to investigation. I also had fast idle for many years and the infamous "chug chug" from the exhaust while idling since I bought the car 10 years ago. Found this post, got the capacitors and, well, although no signs of physical leakage I changed them. Now it idles perfect, sounds different when I tromp it and seems to have much more power. Still have to see if it will shut off
Many thanks to the contributions to this thread.....wonderful!!!

JoshBee

Thanks for all the awesome information guys!

I have a 1uz conversion in my '91 hilux, and even though I checked the caps before installing my ecu (which looked fine) I started to get erratic problems that seemed to multiply. After remembering having previously read this thread, I decided to re-read it and saw I had a lot of the symptoms, along with a strange choking under load at around 2000rpm. The revs and speed would drop and nearly put me through the windscreen! But dropping it back a gear, it would take off again.

Long story short, the caps had started leaking and I replaced them with the ones recommended, she's like a new car!

I have a Japanese delivered(?) ecu and have recorded the caps if you guys wanted to add it to your list:

ECU 89661-50170

2x 10uf 50v 105deg (c103, c104)
2x 100uf 10v 105deg (c105, c108)
1x 220uf 16v 105deg (c106)
2x 15uf 35v 105deg (c831, c832)
1x 47uf 63v 105deg (c740)


Thanks again, this had to be one of the most helpful threads on the net

Yamae

Thanks for the report, outdone. Sounds like your SC400 has been having the problem for more than 10 years without leaking the liquid from capacitors. Your report will be encouraging those who are hesitating to replace.

Yamae

Thanks for the report, JoshBee. The symptom strange choking at certain rpm is not a common problem but it happens when the ripple is frequency dependent.

Anyway congratulations on your fix.

outdone

Thanks again Yamae and Cowboy for continuing your presence and input on this thread. My Lexus is a Canadian car so only comes out like the bears in summer! I'm fortunate to have electronics experience so it wasn't that difficult although I wouldn't have known about the special capacitors.

It was through a forum thread that I discovered I could fix my automatic climate control on my 1982 Mercedes using a soldering iron because of cold solder joints

The SC400 is a special car. I had a terrible hesitation/shaking between 80-90 kms/hr only to find out I had ONE spark plug wire shorting to ground to the engine block. Its still a fantastic car!

Cheers!

700bones

Thank you Yamae and all contributors to the thread who have given us this valuable information!
My capacitors had no sign of leakage but I replace them anyway.

I changed out 8 capacitors on the ECU for a 93 LS400 using the information in this thread. Just a heads up to those who want to do this, be sure you have a soldering iron that can get very hot (mine goes to 450 deg C) as these ECUs apparently use ROHS solder, and it is very old solder at that (the joints harden/oxidize as they age). It made for hard work in removing the solder and old capacitors. I have soldered professionally at JSTD-002 certification, making parts for military aircraft (ROK F-5 among them) and ground systems.

I consider this to be a somewhat challenging project, FWIW.

BTW, I have a similar problem with the instrument panel. I am aware of the threads with the related fix. However, after disconnecting the battery and doing this fix over a 24 hour period, when I reconnected the ECU, all instruments on the IP worked right away(the fuel gauge has NEVER worked before this, the speedo and tach work after a few minutes of warm up usually). They only worked for that first short drive, however. After that first drive, they went back to their normal mode of malfunction (speedo, tach and temp working but fuel NOT working).

Biddles

iTrader: (2)

Hmm.... I wonder if it's possible my transmission is ok, and it's just the ECU. I will have to drive the car a few more times then before buying an ECU.

Has anyone experienced poor transmission shifts after replacing the ECU that eventually cleared up? I've only given it two 5-10 minute rides since popping the ECU in as it's not registered or insured.

KJG92

A great read. I'm almost certain that the car I just picked up needs this done. It is not a job for me though but I'll make sure I get the right caps.

OKSTANCE

so if my board has nasty corrosion still on it after i replaced all the caps and still have issues..im thinkin i may need a new one =/

KJG92

Sorry to ask this but in the 79 pages in this thread is their a page that has a recommend rebuilders list? I know for a fact that this repair is over my head but I want the job done right. Thanks.

ChaosMaker

Hi,

Yes, it is difficult to get the old solder melted, but I think it's because the board is a multilayer and have thick ground and power planes in middle that suck away the heat.

Be careful with the new capacitors, and don't heat them too much. Nichicon specified 380ºC for 3 second max. for hand soldering.
The multilayer board makes difficult to get the solder in both sides without heating them too much.

I just replaced all the ECU and instrument panel caps, I'll try it in the car tomorrow

Yamae

The ROHS solder was not introduced yet for your 93, you must know. The circuit board is not designed for that solder and using it may cause problems in a long term use. Many ROHS solders tend to cause whisker and crack problems and the circuit boards have to be designed and made not to cause those.

Regarding the instrument panel cluster, It is not discussed here. I think you can find some cluster threads somewhere in the forum.

ourbudd

I have been working on my ECM, I have had the P1600 code for some time and I pulled the ECM and replaced all 6 of the caps as outlined in All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor), one leaked on the board and 2 others were leaking some. I bought the new caps and did the replacement and all went well, I reinstalled it and initially the code was gone but around the 3rd day it came back. I am quite sure my work was good, and after installing the new ones I looked them over good with a 10X loope. Do you think I should change them again before looking for another ECM? My plates are now expired and wont pass with any MIL light on so I am trying to figure out where to go from here? Note, I also have a P0430 code Catalyst System Efficiency Below Threshold (Bank2), I will look into this more but any suggestions are welcome, I replaced the cats along with the exhaust last fall and don't think there are any leaks but will check deeper this weekend. Hopefully people can see this because I can't go past page 79 (of 81) in this thread?

Any Help is appreciated, Thanks, Tim