Ok, took off head and now I've got concerns. L20b

[wayno]

Thank you Wayno, question, how important is that bypass if I'm running a non water heated intake mani?, it is an L20b housing with hole in the stat.

If it is an L20b thermostat housing, where does the hose outlet coming off of it go?

This is very confusing, you say you have a L20b thermostat housing, but your running a thermostat with a hole in it, and by the way, a jiggle valve is not a hole.

[Draker]

His work is outstanding, Craig, i was looking at the heads he's done rebuilding and they look better than what new factory head does, his shop is impressive, thank you for pointing me that way :thumbup:

No problem! A bit of a drive.. but what a hidden gem of a shop. Glad he still running the place.

[KoHeartsGPA]

If it is an L20b thermostat housing, where does the hose outlet coming off of it go?

This is very confusing, you say you have a L20b thermostat housing, but your running a thermostat with a hole in it, and by the way, a jiggle valve is not a hole.

If i was at home I'd take a pic, found this one on my album though, i have the aftermarket temp sensor where i believe the bypass should be....

 

[datzenmike]

 If running a dry intake and your by-pass has the Y or T in it just seal it off the line towards the intake.  There should be a fitting on the thermostat housing still that should be connected to the lower rad inlet. Here... lower right

 

 

The by pass is important during warm up only.

 

The thermostat is a long way from where the hot water is on an L series. The engine warms up and gets hot but the thermostat is surrounded with cold stagnant water and stays closed and the gauge reads cold still even thought the engine is getting hot. To fix this the engineers have a small opening in the thermostat housing to let water out and back to the pump inlet. Now there is circulation and warmed water is constantly moving past the thermostat so it can 'sample' it. Engine warms up and the thermostat knows about it right away.

 

Yes you can drill a hole in the thermostat, this will work except that the water is going to the rad and displacing cold rad water into the lower rad hose and into the pump. This is the same as the thermostat stuck partly open and slows the warm up of the engine. By piping the by-pass water directly to the pump inlet the warmed water circulates back and speed the warm up.

[KoHeartsGPA]

Gotcha, makes perfect sense, i will correct it and find another spot for the aftermarket temp guage sensor, thanks guys! :thumbup:

[wayno]

See the hose coming off the thermostat housing in the photo below that the vacuum advance connection is pointing at, do you have this hose/fitting on your thermostat housing?

[KoHeartsGPA]

Update from Bob!

 

Held pressure just fine, no warping, he tore it apart and comfirmed our visual suspicion that the guides are literally gone, to a degree in witch he's never seen before under in his 50 years working on heads, he believes whomever did the work used very bad quality brass guides, the intake are by far the worst, so bad it damaged the valves themselves, exhaust are just starting to seap and valves are within specs with wear however, the cam spins freely and is in great shape, valve seats are steel and in great shape.

 

He asked me if i wanted to get the parts or he can at no extra cost to me, i told him to go ahead and hunt them down, so he's going to call me with the options and estimates on parts and labor.

 

Head hadn't been surfaced more than once according to the measurements he took, problem is that the one time it was done really was not done right, he doesn't think will need to shim the towers but only after he resurfaces and measures again we will know.

 

I'm stoked the head is good :thumbup:

[datzenmike]

If you have an L20B thermostat housing use the hole for the T V V thermal vacuum valve fitting on the fender side for the after market sender. The T V V is a vacuum leak that closes and allows vacuum advance and EGR vacuum to pass only when the engine is warm. You can do without this. The by pass fitting should be beside the stock temp sender, well usually. 

[KoHeartsGPA]

See the hose coming off the thermostat housing in the photo below that the vacuum advance connection is pointing at, do you have this hose/fitting on your thermostat housing?

I see, Wayno......no mine doesn't have the hole for that elbow, it's sealed there.

[KoHeartsGPA]

Bob just called back, parts + labour $560.00 all new valves, guides, shims, resurfacing etc, etc.

 

I'm stoked!

[Draker]

I've got an L20 lower housing

[Draker]

left:

 

[KoHeartsGPA]

I think my lower one is fine to add the bypass, i just need to removed my plug, unless im missing something, god knows, shit i got all of this from Julian and he ran a turbo on it...

 

 

And no that white plastic is not the plug LOL that was a temp plug til i got the AN plug for it ;)

[wayno]

I see, Wayno......no mine doesn't have the hole for that elbow, it's sealed there.

Then you need a thermostat with an eighth inch hole drilled in it.

You likely have an L16 thermostat housing, I tried using one on my LZ23 to clean up the engine, it over heated one day while driving 50mph down a straight road, I let it cool, put more water in it, and I was good for a couple weeks till the head gasket went.

The whole time I had that L16 housing on the engine the temp gauge was all over the place, especially on the hiway, it would climb to the red almost, then drop almost to the C, and then slowly climb to the red again, then repeat that scenario over and over, one day it didn't drop, it just went all the way into the red.

I switched over to the L20b thermostat housing with the bypass hose and never had an issue again, but I also changed over to ARP head studs, I got tired of making LZ head gaskets.

All you need to do is drill the thermostat(jiggle valve don't work), or put an L20b housing on it, and connect that outlet above the lower radiator hose to the bypass outlet and you are good to go, either way should work, but Nissan put the bypass hose there for a reason,

[Draker]

I'll need to look at mine.. I don't believe I have the bypass hooked up either.. but I shall

[KoHeartsGPA]

Thank you Wayno, I'll get the bypass squared away.

 

Draker, i don't think you do either, can't recall seeing it....

[KoHeartsGPA]

Done, ordered 2, OEM Nissan, it's always good to have extras incase someone needs one.

[wayno]

Done, ordered 2, OEM Nissan, it's always good to have extras incase someone needs one.

 

Look at the thermostat closely, if it don't have a hole in it, you need to drill one, as sometimes part numbers get updated to the next part that is compatible(it will fit), the original OEM L16 thermostats had a hole in them.

[KoHeartsGPA]

Bob just called me, head is ready to be picked up :frantics:

 

I also had the coolant passages to the intake manifold blocked off since I'm running side draft setup, no need to have that as a wildcard :thumbup:

[racerx]

That's good.  Feels good that your dime will be on the road again, doesn't it!

[Draker]

Yes!! 

[G-Duax]

Look at the thermostat closely, if it don't have a hole in it, you need to drill one

 

This !!

I do this on all my engines.

Allows getting all the air out of the system quicker.

Hole needs to be toward the top when installed.

[KoHeartsGPA]

So....drained the oil and pleasently surprised there was no coolant present, doing clean up on the surface of the block for the freshly rebuilt head, no pictures of head yet, didn't make it in on time yesterday to go Bobs :(

 

 

I inspected the thermostat housing....yes i it has the bypass inlet hole (lol at my n00bness) damn i sure as fuck couldn't recall seen it.....I'll plumb that up upon reassembly :thumbup:

 

[flatcat19]

(lol at my n00bness)

[G-Duax]

No........

A bypass hole in the thermostat it's self, not the housing.