D1 overheat issue?

DISCO GUY

Member
Dec 7, 2007
20
0
My 98 D1 is overheating . I removed the thermostat . And still overheats . What else can I check ? Any info would be greatly appreciated !
 

p m

Administrator
Staff member
Apr 19, 2004
15,617
838
58
La Jolla, CA
www.3rj.org
If it has seen the red end of the temperature gauge more than once, you can safely plan on replacing the head gaskets.

Other than that... removal of thermostat is rather a useless "last resort" deal.
Make sure that
- the radiator is free-flowing (IR gauge may help); most likely it is half-plugged with scale;
- viscous fan clutch is operational (the simplest way to do it is to buy a new one);
- no fan blades are missing, and fan shroud is present;
- water pump works and pumps coolant around;
- and the system is bled of air properly.

If you're here and the truck is still overheating, it's either head gaskets or new block time.

Out of the factory, D1's cooling system was designed with a lot of cooling capacity - and that resulted in people not maintaining it for many years, and passing barely-working truck to the next owner.
 

ezzzzzzz

Well-known member
Apr 22, 2010
604
7
SE Va
My 98 D1 is overheating . I removed the thermostat . And still overheats . What else can I check ? Any info would be greatly appreciated !

You'll need to provide more info like when does it overheat, what are your specific symptoms? Did it happen overnight or were there progressive signs? As mentioned, most of these have never been properly maintained. Usually these 4.0's will take a good amount of abuse before being worthless. Radiator, hoses, thermostat, fan clutch and water pump are typically changed out to eliminate the problem.
 

DISCO GUY

Member
Dec 7, 2007
20
0
It takes about 13 miles before it starts to over heat. I just replaced the fan clutch and no luck. Can a water pump go bad? Also how hard is it to flush a radiator out ? It does cool down if I run the heater & a/c.....:banghead:
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
It takes about 13 miles before it starts to over heat. I just replaced the fan clutch and no luck. Can a water pump go bad? Also how hard is it to flush a radiator out ? It does cool down if I run the heater & a/c.....:banghead:

Yes, a water pump can go bad. There are only a handful of components in your cooling system and if they are all factory originals then at this point your engine is living on borrowed time. Flushing a 15-20 year old radiator is not worth it. You can buy relatively inexpensive aftermarket aluminum radiators that work well - I have had good results with this option. Replacing the water pump and VCU is a good insurance policy. Also buy a ScanGauge or similar auto diagnostic computer that allows you to read your engine coolant temps live because the dash gauge is useless.

Between a radiator, water pump, VCU, and reader you could be looking at $500 - $600 and all removal and installation is pretty easy. That will keep your engine running comfortably for a long time and could save you the headache, hassle, and expense of a head gasket job.
 

DISCO GUY

Member
Dec 7, 2007
20
0
Problem solved ! It was the Radiator ! If anyone has to replace there's I
Highly recommend a APDI from rock auto . It is the best alternative to oem!
And it only cost me $403 !
 

n8thgr8

Well-known member
Dec 6, 2006
587
0
Colorado, Guam
I"m gonna hijack this thread...
Going back to the clogged cats being incidental to overheating...
I had overheating problems for years, and eventually piece by piece replaced the entire cooling system and did the head gaskets. BUT could having overheating issues for so long cause a problem with the cats? if so, could a clogged cat produce bad readings with O2 sensors and throw codes ?