That is a very slightly low coolant temp ..... but maybe not enough to cause a hot exhaust 'slow down ligh' (assuming the vecovini system is reading correctly) ....... it might be a good idea to see if your fuel pressure regulators are able to hold vacuum ....... as you may already know ... they are buried in the front of the throttlebodies .......... if they do not hold vacuum, they will not back off the fuel pressure at idle or part throttle (vacuum) .... that would cause a rich condition ....... I checked mine with a fuel pressure gauge then pulled the regulator vacuum hose off/on to see the change in fuel pressure. But a standard external vacuum hand pump will see if the internal diaphragm has a leak. Also to check on the LH thermal fan switch and gauge .... at what temp does your LH fan kick on? May be a good idea to change the ECU coolant temp sensor (#40 on the parts pic of the previous page). They are inexpensive and the main source of engine temp reference for the ECU. Do you have any black soot in the exhaust tips? a lot or a little? check with paper towel in the exhaust tip with engine off yeah man ... just tryin to bring more info to fellow owners ...
Seems the majority of the votes are right with me.....are we thinking the majority of people have a problem with their cars? I have another theory that just came to mind on my slow down light. A variable I forgot about... My headers, cat pipes, and bypass pipe are ceramic coated. Maybe they are holding more heat in the pipe than before, which is the whole purpose of the coating........??? It can't radiate out as much therefore the thermocouple would be hotter. Also when I go faster the car pulls more air into the engine bay which would cool the pipes externally a bit more and help cool things down.....just some new thoughts.
The ceramic will not hold in that much heat and certainly not more than the factory shielding and insulation. Did you check some of the things mentioned on my previous post?
Other possibility is the guage is getting the wrong reading from the sending unit My guage vs reading temp off the ecu is about 7-10 degrees different Got the love the hmmm "uniqueness" of each car
It's interesting that you mentioned: "Do you have any black soot in the exhaust tips? a lot or a little? check with paper towel in the exhaust tip with engine off" On my Capristo, the closed bypass valve path looks whitish and lean and the open bypass valve exhaust tips are black and sooty. It seems it's going from too lean to too rich, is that what you would conclude and how would you fix it?
according to your OBDII scangauge your temps are right within spec ............ so it seems your t-stat and ECU coolant temp sender are good ... For reference assuming the 355 gauge/sender is accurate and the increments are linear ........ the temp delta between each 0-20 number on the illustration ...... is about 5.83°F As mentioned this thread is for information, awareness and precaution ...... I wanted to share what was found on a few 355s that had some subtle 'rich running' related issues ..... that were absolutely corrected by getting the coolant temps within spec
It would depend on how much soot is in there, if it looks thick velvety black then there may be an issue ........ is there any other symtoms you have? .......... how are those coolant temps ?
Mine tends to run hot. In slow traffic w/ AC on it can run all the way towards 19 or 20 on your scale and will cool back towards 190 on the highway.
Understand that on the Capristo, the bypassed exhaust path does not go through the main catalysts, thus the sooty looking tips. The tips that the exhaust goes through the catalysts looks very clean. Each pathway is independant, with a seperate chamber for each path. By comparison, most other brands (and oem) exhaust, both pathways share the muffler can, thus the exhaust is mixed, prior to exiting the tips. Image Unavailable, Please Login
Jevs, for the slow down light issue try this. Get the ECU to relearn its parameters. Oz told me how. You reset the ODB Codes with the Scaner tool, fire up the engine to make sure check enging light is cleared. Then disconnect your battery using the shutoff in the boot compartment. Let the car sit like that for several hours, preferably over night. Next day when you start the engine let it warm up and then drive it about 20 miles keeping revs under 3000. Lots of short shifting to accomplish that but it can be done. That's what I did and the slow down light never came back.
exhaust soot aside for a moment .... 19 or 20 is waaay too hot ........... I think one of your fans not running ........ when at 12 or 13 and car sitting on idle ..... on each side rear door jamb vent, listen for your fans ....... then post back what you find out!
+1 .......... this one also uses independent paths and chambers for mains and bypass ............. Image Unavailable, Please Login
I've checked the fans multiple times even had 1 replaced, consulted w/ several mechanics and have been told that's the way it is. I'm now going to pursue it again and ask to change the t-stats, etc. I'll let you know what happens. Thanks
Does anyone know of a source for the 86dC thermostate from the 328? Ugh, this thread just gave me 3 more things to buy and install. My temp would sit at 6 on the scale cruising on the freeway.
GT Car Parts in AZ definitely have the BEHR 82°C and may also have the 86°C 328 version ........ but since you are at 6 ........ either one will be an improvement . CGT Car Parts contact info: http://www.yellowbot.com/g-t-car-parts-inc-phoenix-az-1.html Their site: http://gtcp.com/ After you get the new t-stat installed ....... please report back any differences in the coolant temp gauge, as well as 'driveability' changes, improvements or anything else you may notice. .
Make sure the fans blades are actually turning. The fan blades on 355 fans have been known to break loose from the motor shafts. Motor spins and makes noise but the fan doesn't rotate.
Hey Scott, thanks a lot man!!! it is freakin' great to hear from you !!..... things are getting better and am working to get things moving again ...... !!
I replaced my thermostat on my 95 355 this weekend and drove it this morning on the highway in 60 degree temps. Nomally my temp gauge would be at 6. This morning it was 8-9 so now in the normal temp range. On really cold days, 40 degrees, it would be in the 4-5 range. It did this for several years--hated to take it out on cold days and always thought there was so much air flowing over the radiators that this is what caused the low temps. Thanks Goth.
That is great to hear Bob !! 8-9 on cruise is perfect .......... if you are running cats ...... they will be very grateful with the change ......... you should also see lower exhaust temps overall.
I used the 82 degree. GT Parts said they made a 86 degree but when talked to the owner, he said that info was wrong. They only make a 82 or a 74 degree which obviously would not work. It was a Behr thermostat.
I would recommend the 82°C thermostat, as that is what the factory installed ... Just to reiterate, this thread was primarily to identify a faulty or weak thermostat. If your 355 goes any lower than 82°C or 179.6°F at any time after full warm up, there is a problem. Look into it. Also if your 355 goes below that 82°C point, then goes back up into the 'good range' during a change in driving style or conditions, it does not count ....... going 'back up' does not mean everything is fine. Running below 82°C at any time after full warm up, will cause a rich condition and will hasten the life of the catalytics and exhaust components. ** The gauge diagram and scale are for reference only. If you have a more accurate method of measuring the coolant temps, then all the better. 1 --- 137.50°F 2 --- 143.33°F 3 --- 149.17°F 4 --- 155.00°F 5 --- 160.83°F 6 --- 166.66°F 7 --- 172.50°F 8 --- 178.53°F * 9 --- 184.16°F 10 --- 190.00°F 11 --- 195.83°F 12 --- 201.66°F * lowest point after full warm up, with cool conditions and modest driving. and to repeat, a correctly functioning thermostat is set at 179.6°F or 82°C ** During this troubleshooting, it was noted that a bad thermostat would create an abnormally rich condition during initial warm up as well. One of the ways it would manifest was with slow 'slow down' light within a couple minutes after a cold start. These cold start 'slow down' lights went away after the thermostat was changed. Image Unavailable, Please Login
Mine goes as low as 8 on the highway and as high as 13 in traffic. This is in Houston so it's usually in the mid to high 90s or worse. Should I get my thermostat changed?