How To Bypass Throttle Body Coolant Housing

[5Toes]

Wait a minute, why does a hole need drilled?

[jeffnhiscars]

Wait a minute, why does a hole need drilled?

Older engine all have some blow by which settles in the intake manifold and runs down the throttle shaft into the TPS fouling the contacts. The hole lets it out before it causes issues. I've done all 3 of our M20's recently. 2 had oil in them and one had so much Im surprised it survived.

You drill a 1/16 or 1/8 hole just above the "S" in Bosch which puts it at the center of the shaft or better yet remove the TPS, drill from the TB side, thoroughly clean, test & adjust it, throw in the new gaskets and a new TB to intake gasket.

[5Toes]

So you drill into the throttle switch itself?

[jeffnhiscars]

So you drill into the throttle switch itself?

Correct..just a small drain hole in the center of the plastic cover which is the lowest part of the TPS when installed. Right above the "S" would put it dead center if you happen to drill from the outside. I did it from inside.

Note: Stock pic reproduced without permission :-)

[1ball]

great fix... just what i needed for my 89 vert w/75K orig. miles

[Ether-D]

I did this on my first e30 back in 99. But I fixed it properly on my current one. I had no problems with the bavauto gasket.

[shelleyd73]

Thank you for the detailed write-up. I did this a few weeks ago and it worked perfectly and solved a big problem. :-)

[garagistic]

We also did a similar write up. Just used a different method:

http://garagistic.com/index.php?page=m20-thermostat-housing---throttle-body-heater-delete

[efficient]

We also did a similar write up. Just used a different method:


http://garagistic.com/index.php?page...-heater-delete

This seems like the best idea.

[Thizzelle]

this fucking hose is annoying

[Swendog]

Great write-up. But I agree in keeping it "correct" and using the bypass as temporary fix until you can replace the TB heater gasket. I did the bypass, but did not cut the hoses. Will order the TB heater gasket and fix it when car is down for other repairs.

On a separate comment, one of those hoses connects to the block near the firewall- it appears that you would need to remove the intake manifold to get to the hose clamp. Anybody out there ever replace that hose without removing the intake manifold?

[Norbert]

Guys. How about putting around the gasket which you buy new a thin layer of some sort of hermetic and you just connect it and vuala? I mean i do that pretty much with all gaskets o.O A tip given by a car/motorcycle engine hardcore tuning expert. Or if no hermetic, normal grease works fine. hmm?

[bmrsehen]

Make your own gasket

That cooling throttle body gasket has failed on me twice in a row right after T Belt Service - both times the water pump was replaced (and coolant too of course.) Those cork gaskets never last.......I guest the engineers look at that as a "cheap" failing point. I bought a new cork gasket (used it as a template) and made my own gaskets from two different gasket materials. I went with a (pink) rubber gasket mateirial. I used razor/exacto knife, scissors and a small file set. It was time consuming, about an hour or so. I did this because I tired of getting stranded with a coolant leak and an over heating engine. When my leaked it came out quickly. So far it has held 5 years. I need to change the T Belt. We will see what happens. I think using a better gasket material will make it last longer. The only down side I see is that that it is no longer a weak point and now a radiator or hose etc will fail instead but those parts fail too. see pictures....left -OEM Cork, middle and right are my "home made" gaskets. I went with the rubber material gasket (pink) on the right. It is almost twice as thick but it works.