allmazda

Have not done much with the 99.

First, what is the part called that the coolant hose from the back of the plenum goes into before it goes into the throttle body?

Is it the EGR volume control?

I did not like the color of the coolant that came out when I removed the lines. I guessing there is a blockage in one of the coolant hoses. I am going to replace the hoses and flush the system but this setup is different from my 95 fed spec.

allmazda

It appears it is the EGR valve....

Has anyone removed the 3 bolts on the top?



This pic is from ebay mine is still on the car.

I want to replace the 2 coolant hoses. The coolant hoses were clogged going to the TB. As well as the rear of the plenum.

CS_AR

I've replaced the EGR on a 99 model. The 99 uses an electric EGR made by Hitachi. I used an Intermotor part that is the same Hitachi part that I replaced. Also I bypassed the coolant u shaped hose.

Here are a few pictures of the coolant hose bypass around the UIM u-hose.















If you need a new EGR valve, you can get an Intermotor at Advance Auto for $99 using discount code OFRAAPSP.

I can tell you with all certainty that a failing EGR valve on a 99 model will make your life miserable and not throw a code for weeks..

allmazda

Thanks....

So if I am seeing it correctly you ran this hose to the coolant nipple that is closest to the engine.



The hose marked in blue goes to the nipple closest to the engine on the egr valve and the one closest to the fender goes to the same location at the TB?

Mine egr is fine. I removed the plenum to change the valve cover gaskets. Then noticed the clogs in coolant hoses.

allmazda

On a side topic but related.... what is the purpose of the U hose?

I bypassed mine on the 95 but there are no coolant lines on the EGR.

Does it help cool the EGR gases entering the intake or does it heat up the lines going into the TB?

CS_AR

Correct. You can see the textured "high pressure transmission fluid" hose (blue mark) going to the EGR nipple closest to the engine where the one closest to the fender routes into the nearest TB location.

J. Holley and I use high pressure/temp ATF coolant hose for bypassing the UIM u-shaped hose.

On the side note, I have no idea why the U shaped hose runs through a pipe on the UIM. To me it looks like an effort to save manufacturing costs.