Page updated on 04-19-2018

1998 Rodeo Thermostat Location & Replacement

10-01-2004, 08:30 AM
Has anyone ever replaced the thermostat on a 98 Rodeo 3.2? If so, can you tell me where it is located and is it something that I can do myself, without taking the engine apart?
Thanks, Jeff

10-01-2004, 11:00 AM
Pretty sure it's buried under the intake manifold. Have to take the IM off to get at it.

95.5 Rodeo
10-01-2004, 11:48 AM

The newer Isuzu 3.2 engines must be redesigned if the thermostat is located under the intake manifold. My thermostat is right in front, under the coil packs and connected to the lower radiator hose by a "chevy style" water neck.

I know because I replaced it about 2 weeks ago during a cooling system service. The part was about $23.00 at the dealer. I get a discount there, so my cost was a few dollars less.

The coolant gauge was indicating halfway or better on the scale, now it goes up to about a third and stays there. The radiator hoses aren't nearly as hard with pressure as they used to be and the engine is much happier with adequate cooling.

When I was flushing the system, I couldn't run the engine with the radiator cap removed, the water would gush out like an erupting volcano. This was before I replaced the thermostat.

Another thing- the radiator's drain plug is located in a terrible position and is virtually useless. I ended up pulling the lower radiator hose to drain the water / flushing solution, this worked much better.

When installing the new part be sure the "Jiggle valve" is in the up position and the spring / wax pellet is pointing towards the block. Does anyone know what a "Jiggle valve" does?

BTW, I always use distilled water to make up the 50/50 solution. This will keep minerals from building up in the cooling system.


11-30-2004, 07:30 AM
I have a '98 Isuzu Rodeo as well w/ a thermostat problem and was told by the mechanic that the engine would have to be taken apart to replace it. I'm not sure if he's right or just schisty, but this is what I was told.

11-30-2004, 12:57 PM

The newer Isuzu 3.2 engines must be redesigned if the thermostat is located under the intake manifold...


Yep. They are. The blocks are pretty much the same, but the heads, intake/common chamber are such that the T-stat is buried under there now. One good note is, the radiator drain valve is real easy to get at & use on the 1998!


12-04-2004, 11:22 PM
I drained using the bottom hose, too. The PIA part of the job was the engine block drain.

Add your comment to this topic!