metal pipe from heater bypass valve to PHH

Cattledog · 02-20-05, 01:00 PM

I bought my lx about a year ago with 103K. All services were recorded by the Lexus dealer. The PO had flushed the cooling system with green coolant. So two months ago, I flushed my 1996 lx like the FAQ had suggested and switched to Toyota red.

During the flush I found gray sludge....

About a week ago I noticed many slow leaks around the heater core pipes and PHH. Nothing was leaking before the flush. So time to replace heater hoses...

The question is what is the function of the metal coolant pipe that connects the heater bypass valve and to the PHH? The heater bypass valve is attached to the upper firewall and to a short 90 bend heater hose that connects to the metal pipe which is attached to the engine via the PHH. Those hoses must flex allot. It would be understandable for the hoses to leak after 100K miles.

Why should I not replace the entire metal tube and hoses with Silicon heater hoses and constant tension clamps? I also understand that the egr pipe is next to the metal coolant hose. Silicon heater hose should have no problem in that environment. What do you guys think?

Also take a look at http://www.gates.com/brochure.cfm?br...ocation_id=541

the link is about galvanic corrosion and EPDM heater hoses.... And yes the heater hoses in the FZJ-80 are EPDMK rubber. I am very interested in the condition of the old hoses. The hoses may be the source of the sludge in the cooling system. BTW I am a chemist by profession, may be some testing is in order on the heater hoses.

I wonder if Toyota had changed grades or source of heater hoses from the 93-95 to 96-97 models? Could someone with a 93 original heater hose that attaches to the heater bypass valve snap a pic. There should be a part number and grade of rubber used in the hose.

Thanks
Dave

landtank · 02-20-05, 01:20 PM

One nice thing about the metal pipe is that it won't chaffe against anything to create a leak. I've replaced my PHH twice now and just regular ol' hose. I don't find it that big a deal to change it out.

Cattledog · 02-20-05, 01:31 PM

Another link about coolant hose failure. http://www.heavydutytrucking.com/2004/11/124a0411.asp

Could the EGR pipe be causing PHH issues? Is the EGR routing the same for the 93-95 as th 96-97?

Landtank, I am lazy I only want to R&R that hose once before a full rebuild of the engine. Hopefully 200+K away.

I could be that a small heat sheild would solve heat issues at the back of the engine.

Rich · 02-20-05, 01:51 PM

Dave, Other than short piece of hose (PHH) between the head and the metal pipe that runs up to the top of the engine I wouldn't worry too much. Given the time and effort required to replace the PHH I used Gates Greenstripe hose, which I expect to be much more durable than the Toyota hose. It is more immune to physical damage and less likely than silicone hose to leak when cold. It is a bit more trouble to install.

I don't think EGR is an issue with respect the PHH, it is not anywhere near the EGR pipe.

Regarding the gray sludge, take a look at http://forum.ih8mud.com/showpost.php...1&postcount=60 to see what I have filtered out.

Cattledog · 02-20-05, 02:06 PM

Landtank, does the EGR route right behind the #6 cylinder head /block interface? I know you replaced your HG. How much room do you guess is back there between the firewall EGR and the head? Your thoughts?

landtank · 02-20-05, 03:48 PM

The egr goes through the head, there is no pipe back there. There is a pipe that attaches to the head alone side of the intake and travels up to the egr valve.

The PHH is like an hour to an hour and a half job. The biggest pain is draining the system. Besides I think it's worse out west as they don't have an occasion to use the heater and with the valve closed all the time the water at the PHH gets hotter for a longer time than when ciculating at least a few months out of the year.

Cattledog · 02-20-05, 04:31 PM

Thanks landtank

dclee · 02-21-05, 11:44 PM

Quote:

Originally Posted by landtank

One nice thing about the metal pipe is that it won't chaffe against anything to create a leak. I've replaced my PHH twice now and just regular ol' hose. I don't find it that big a deal to change it out.

I concur. PHH was not too much trouble, although I chose to use the Gates super-stiff stuff, that made for some cursing...

However, the ones I'm really afraid of are the heater hoses on the firewall, behind the head. The ones way down there that you can't see very easily. I fear them so much because I've changed them out, and have many permanent scars on my hands and arms from that job. PHH is child's play by comparison, IMHO...