1. Home
  2. Automotive Technologies
  3. how to diagnose problem w/ cooling system?

how to diagnose problem w/ cooling system?

hello, '89, 4 cyl; fuel injected (MPI); 70,000 miles (lightly but regularly driven) runs well on highWay. just got *new* o2 sensor and *new* fuel filter (computer tested?) when the car warms up (very quickly -- 4 minutes while standing (idling) ) rough idle, hesitation... however tested the battery voltage off: 12.52. on (cold) 14.37 + ventilation (air) 14.25; + lights 14.25 then switched to heat : fluctuates (14.10 14.90 ) warm: (did not move the auto) battery only: 14.24

  • lights (rpm decreased by 1000) voltage = 14.27
  • ventilation: (cool / normal air temp) rpm decreased by 2000 (did not come up) and battery voltage was 12.6 with vent changed to heat voltage was 12.10 could someOne possibly explain this? the several questions:
  1. it shouldn't get warm that quickly sitting in the driveWay should it? (it is not a hot day)
  2. when it is warm the voltage with the ventilation dips to 12.x (and yesterday when i tested it after driving it, the battery voltage was
14.x with tape player and lights but dipped to 12.00 (it wavers / fluctuates) and isn't 12.0 the limit for driving?) (this was in park) (although being warm i guess i have to add a bit to the measured voltage?)
  1. this is not a charging system problem is it? could it be the a/c belt? could it be a short? (but wouldn't a fuse blow?)

i sincerely apologize for ruminating about this auto (chrysler / mitsubishi / dodge colt 200 (2000 series) but as mentioned i am getting nowhere...) thank you for any and all replies (p.s. i had hoped that when warm, turning on the interior heat would cool the engine (by transferring heat into the car?) and had assumed that the voltage would normalize if the engine was being cooled that way but that did not occur:)

-- to reply: userName: tjtmd domain: attglobal.net and separate the 2 words with the at sign:)

Reply to
tanya
Loading thread data ...

I would guess you have a dirty connection on one of the main battery cables. The ground to the body or the ground to the engine comes to mind first.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

tanya wrote:

Reply to
Mike Romain

-- to reply: userName: tjtmd domain: attglobal.net and separate the 2 words with the at sign:)

Reply to
tanya

Just theory here, tanya. IF the ventilation only changed the vacuum 'seal' (by, say, bleeding off some of the usual source to allow a vent door to open or close), the rpm's might change enough to make the voltage go up/down depending on which way the rpms went. On a steady load, it may be calling for maximum voltage/amperage output; adding an additional load will make it stay at this maximum output as it is still calling for "maximum". This assumes the additional load did not alter the rpms significantly, like a change in vacuum at idle might do. Hope this makes a little sense & good luck. sdlomi

Reply to
sdlomi

Maybe your heater motor has a short producing a huge load. Your voltage should be stable in the 14V area regardless what accessories you turn on.

Reply to
WasteNotWantNot

The ventilation motor is one of the biggest power draws in the vehicle next to the starter.

A corroded ground can let a light power draw pass fine, but when the big load is put on the connection goes bad.

It is where I would start on an 89, they likely are all due for a good clean anyway and then a bad connection is taken out of the picture so if it still happens you need to look elsewhere.

When I see swingy power levels with various loads, ground connections leap to mind.

Then I think of things like a worn out blower motor once the connections are verified good...

Mike

tanya wrote:

Reply to
Mike Romain

And the ground wire right at the blower motor is the most suspect. I finally soldered mine right to the body.

Reply to
WasteNotWantNot

thank you for the reply! sincerely Tanya

-- toAnswerSend2:userName:tjtmd domain:attglobal.net separate these with the at sign

Reply to
Tanya

-- toAnswerSend2:userName:tjtmd domain:attglobal.net separate these with the at sign

Reply to
Tanya

thanks -- good to know about the voltage with *any* accessory thank you! sincerely Tanya

-- toAnswerSend2:userName:tjtmd domain:attglobal.net separate these with the at sign

Reply to
Tanya

hello, i REALLY appreciate the answers i got very much! thanks! i have to take it back to the dealer to have the electrical checked... when i brought it to chrysler last week the computer diagnosed a bad o2 sensor (it had VERY RICH and visible exhaust and was using more fuel >

normal) the *new* o2 sensor stopped the smell for ~ 2 days...) now the car and exhaust reeks (?reaks?) again of fuel... i did check the oil and it had a bit of black grit in it (but otherwise was light brown) and ?water? but most NB is that the oil smells of fuel very strongly. is this normal? or could it be from (a) bad piston ring(s)? and if so could that have anything to do w/ the voltage and ventilation anomaly? MANY THANKS AGAIN! sincerely Tanya

tanya wrote:

-- toAnswerSend2:userName:tjtmd domain:attglobal.net separate these with the at sign

Reply to
Tanya

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.