DI ovrheat with AC on

BaldEagle

BaldEagle

Well-known member
Sep 13, 2004
2,824
0
Atlanta, GA
just bought a new daily driver, a 98 dI. 118k miles. the engine tries to overheat ( i dont let it) in one situation: with the ac on while sitting in traffic or going slow through town. going down the highway at speed it is fine, obviously enough air is blowing through to cool it down. with the ac off it runs at normal temp. i know your first thought is condenser fans, but they're both turning. in fact i replaced them recently. everything seems to be working right, viscous fan is working. it has coolant, hasnt leaked any. apart from the condenser fans i dont know how the ac is related. any guesses?
 
8

88gspd

Member
Nov 24, 2005
18
0
Bethesda, MD
At 118k miles, it is most likely a clogged radiator. Get it tested at a radiator shop and replace if found to have restricted flow.

You might also want to consider replacing your viscous clutch with a heavier duty one for a 1998 Chevy Blazer 4.3L w/ AC if you don't mind having your truck sound like a school bus.
 
T

Timmy!!!!!!!

Well-known member
Jun 7, 2004
4,585
1
38
Bourbon Street
www.facebook.com
Just have the radiator cleaned out and see if that helps. My local shop charged I think 30 or 40 dollars. I know my 95 overheated and did this and thought it was the head gasket but it turned out to be a clogged radiator. Cleaned it out and put some watter wetter in and it ran very cold. When I got my 97 disco I cleaned out the radiator immediatly and no problems so far even when my electric fans didn't cut on b/c a wire broke.
 
BaldEagle

BaldEagle

Well-known member
Sep 13, 2004
2,824
0
Atlanta, GA
theres no crap between the radiator and condenser, i checked when i replaced the condenser motors. if its the radiator route, any explanation why it only does it with the ac on?
 
garrett

garrett

Well-known member
Jun 18, 2004
10,931
5
53
Middleburg, VA
www.blackdogmobility.com
i have a few trucks that do this, but i rarely run the A/C, so i've left it alone. 50% of the time it's the themostat. with that mileage it could very likely be the radiator as the above have mentioned.
the DI rads are pretty easy to remove. i'd take it to a shop to have it flow tested. but replace the t-stat regardless. $10 in preventative maintenence.
your electric fans are coming on right?

the reason with the A/C on is that it needs the extra cooling and with a inefficient rad or non working t-stat it can't keep up.

toss an OBD II scan tool on it too and make certain the guage is reading properly.
 
Last edited:
BaldEagle

BaldEagle

Well-known member
Sep 13, 2004
2,824
0
Atlanta, GA
i've removed the radiator and had it cleaned on my 96, so i dont mind doing it, not a hard job. i'll change the tstat today and do the radiator over the next week or so. thanks guys.
 
BaldEagle

BaldEagle

Well-known member
Sep 13, 2004
2,824
0
Atlanta, GA
well it wasnt the tsat so i pulled the rad and i'll have it sent to a rad shop to be inspected and likely rodded out. one reason i suspect it is the radiator is the system was under immense pressure when i shut it off, the radiator hose couldnt be squeezed, and when i loosened the radiator cap, after the air came out, a bunch of coolant bubbled out and overflowed. anyone think it could be anything else?
- condensate fans are both running with ac on.
- no oil in water and no water in oil, no other head gasket symptoms like leaks or water in the intake. doesnt use a drop of coolant.
i drive to atlanta from clemson every sunday night, i didnt think it could make it 3 hours without blowing the hoses or the radiator, i'll drive the old trusty trail rig down. i retired it as my daily driver just saturday haha.
 
8

88gspd

Member
Nov 24, 2005
18
0
Bethesda, MD
Hopefully, it is just the radiator. If the problem does not go away after it is rodded out, have your coolant tested for exhaust gases, which might be pressurizing the system.
 
BaldEagle

BaldEagle

Well-known member
Sep 13, 2004
2,824
0
Atlanta, GA
the radiator guy said it doesnt seem clogged but he would boil it anyway since it was out. so lets eliminate that. he said he was working on a rover and the impellar in the waterpump was bad. was does anyone think about that? kind of hard to believe but i guess its possible.

as far as the fan clutch goes, i think its good. the nut on the clutch turns but with signifigant resistnace when i hold the fan in my hand. just like my 96. before i order a pump let me know what anyone thinks. i'll probly buy a pump anyway though just as a PM measure.
 
Steve Rupp

Steve Rupp

Well-known member
Apr 21, 2004
3,213
0
48
Seattle, WA
www.discoweb.org
I don't think you'll notice simply by looking at the radiator how bad it may be. I keep saying radiator because you say it overheats as soon as the a/c comes on. I had this same problem on a 94 that i had. The radiator was on the edge and very rarely overheated with the a/c off. Turn it on and it just couldn't handle it. I know it's not a very scientific theory, but this thread always comes up this time of year, and i've just seen it so many times.
 
R

robertf

Well-known member
Jan 22, 2006
4,796
364
-
There is a big difference on the genuine and non genuine impellers (at least the non genuine one I got)

That could be, but you might want to check for the exhaust gasses before spending any more money. I think once these engines start overheating regularly when under a load the end is near. It was for me.
 
jimjet

jimjet

Well-known member
Feb 22, 2005
3,257
2
L.I.N.Y./Daytona Beach Fl
BaldEagle said:
the radiator guy said it doesnt seem clogged but he would boil it anyway since it was out. so lets eliminate that. pump let me know what anyone thinks. i'll probly buy a pump anyway though just as a PM measure.
Click to expand...


so lets eliminate that.


dont eliminate that.

Mine was boiled and flow tested on my 98 and it still overheated AGAIN.

Just buy a new radiator and do the pump while your in there and be done with it.

When i had my problem it was fine around town , on hills ect ect.
but on a long cruise to work it would slowly creep up to an uncomforatble temp.

I installed Auto Meter temp gauges
The originals just dont work.
http://www.discoweb.org/forums/showthread.php?t=18613

Jim
 
Last edited:
You must log in or register to reply here.
Top Bottom