Running too cold, then too hot.

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 27, 2009

#1

• Aug 27, 2009

• #1

cooling setup; stock w/p with under drives, mark 8 fan, 3-core radiator, 185 t-stat.

on my way to work (about 45 degrees maybe a bit more) the car did not get over 145 degree's cruising at 50-60. the fan is on a toggle switch, and it was OFF. not hot enough to get any heat for my defrost. what can you do when the car wont even warm up?

then after work (85ish i think now) my 50a relay switch fried. so the car overheated, got up to 220* before i could stop. got a new 50a relay at parts store, and the wiring is scorching hot. so its too much for that when i DO need the fan.. will the 75a bosch relay i read about work? what can i go get/order from a parts store, and not have to worry about?

between this crap, my surging idle i cannot get to completely disappear and everything else, im about ready to just go get an 03 cobra again.

 

1991notchbackLX

Active Member

Dec 25, 2007

1,483

47

48

New York

Aug 27, 2009

#2

• Aug 27, 2009

• #2

just don't change the fuel filter...

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 27, 2009

#3

• Aug 27, 2009

• #3

1991notchbackLX said:

just don't change the fuel filter...

Click to expand...

i wont... lol.

do you remember that or something?

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#4

• Aug 28, 2009

• #4

forgot to mention, it is a new t-stat. it is not stuck open.

when i come to a stop, it heats up quickly from 140... 150, 160, 170 within 30 seconds. then i start driving again and it drops down to 140-145.

i tested heater today, we just put the blower boxes back in. it blows hot air with temp gauge at 170, and then i cranked it cold and got cooler air. i was concerned the heater core wasn't working properly, but it appears to be fine.

what can i do to atleast make this run warmer? smaller radiator?

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

33

129

Aug 28, 2009

#5

• Aug 28, 2009

• #5

Are you real sure the t-stat isn't jacked up? New doesn't mean good.

The Bosch 75 Amper will work. I don't know of anything at a parts store that I'd trust.

The wiring should not have been hot - that suggests it's not large enough.

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#6

• Aug 28, 2009

• #6

i recall, reading someone used a 75 amp switch like i have now. except mine now is a 50 amp. i just need something to get me buy right now, if the bosch is a mail order thing.

do parts stores not stock bosch units?

t-stat opened at 185 new. which was roughly 2 weeks ago. i can snag another new one tomorrow and see if it works better.

i have one other stupid question regarding my vacuum lines. i need to hook the one up for the vent controls. ive got 3 hanging in the bay. no ac, no smog, no egr, im just wondering which one i need to get it functioning.

if you read this again tonight jt, ill post a pic of them..

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#7

• Aug 28, 2009

• #7

not sure if your on dialup still or not, http://pic100.picturetrail.com/VOL737/2692743/8343319/372890662.jpg

thats the pic.

ive got the capped one im holding and one other from the passenger side fenderwell. those should both be capped right? only the one is capped from there.

then i have one coming out the back of the firewall. im assuming thats for the heater controls? that line runs over to the vac tree or another location?

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

33

129

Aug 28, 2009

#8

• Aug 28, 2009

• #8

IIRC, the vac line for the AC is labeled AC on the vac tree (I might be thinking of SN95's, which have that labeling for sure).
The one going through the firewall should go to the HVAC, like you noted. If you can test it (with a vac pump of a friend), the other end should be at the vac cannister in the cockpit. Run a new line from the firewall fitting to the vac tree.

I would cap all vented vac lines. YOu don't need extra vac leaks.

Napa should have a HD continuous duty relay that will work for you. It will probably cost more than getting a Bosch relay online.

You could try wiring two 50 amp relays in parallel. I haven't ever done it myself so I cannot comment (though the theory behind it is ok, though not something you want to do long-term).

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#9

• Aug 28, 2009

• #9

ill give napa a shot tomorrow. going to get/order the 75 amp relay, new thermostat and some vac. line.

those 2 lines out my passenger side should for sure be capped then correct? if not labeled a/c? only one is right now..

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#10

• Aug 28, 2009

• #10

i see you edited after i replied. gotcha on the vacuum line. im going to cap the second line from my passenger fender also.

i jumped onto summit, $40 for the 75 amp relay + $11 handling charge.

went onto ebay, got one new for $26 shipped.

so ill get by with my 50 amp switch for now if i drive the car once or twice before the new one comes.

 

67coupe

Founding Member

Apr 5, 2002

658

402

93

Huntsville, AL

Aug 28, 2009

#11

• Aug 28, 2009

• #11

If your Mark VIII fan is wired to high speed, then the 50A relay is not adequate. An electric motor's peak current is at stall speed (0 rpm). So at start up, that fan can pull upwards of 100 amps before it ramps down to a continuous run current of 25-30 amps. In only a matter of time before this fries the relay. This is the main advantage of variable current fan controllers.

If in the mornings, your operating temp is only 145, then the thermostat is definitely bad. With the overheating you're describing in the afternoon, I would guess the thermostat is stuck partially open.

 

281pony

Active Member

Aug 31, 2003

2,681

2

46

Oly, WA

Aug 28, 2009

#12

• Aug 28, 2009

• #12

it overheated in the afternoon from the fan not operating. the thermostat did work properly when new, ill yank it out and replace it. i hope the bosch relay and the thermostat take care of everything then. thanks

67coupe said:

If your Mark VIII fan is wired to high speed, then the 50A relay is not adequate. An electric motor's peak current is at stall speed (0 rpm). So at start up, that fan can pull upwards of 100 amps before it ramps down to a continuous run current of 25-30 amps. In only a matter of time before this fries the relay. This is the main advantage of variable current fan controllers.

If in the mornings, your operating temp is only 145, then the thermostat is definitely bad. With the overheating you're describing in the afternoon, I would guess the thermostat is stuck partially open.

Click to expand...