Bypassing the thermal control valve

[VIN1498]

Hi folks!

My first post here so a quick introduction. I've had my Delorean for 23 years now and have done most of the wrenching myself. The service manuals and this site are a great resource for sure! My car is a very regular driver with 86,000 miles on it when the angle drive went out in 1999 so by now I'm sure it's got well over 120,000 miles. It has always been a reliable car, despite having to live without a garage all this time.

I decided to replace the vacuum lines with silicone ones. Reaching the thermal control valve is a challenge without removing the intake manifold and since I am trying to reduce vacuum leaks instead of create them I am trying to work around it. The ends of the old vacuum hoses at the thermal control valve broke off at the nipples when i tried to remove them. Very frustrating.

Since the distributor and the control pressure regulator are the beneficiaries of the vacuum from the thermal control valve I wondered what the effect on performance would be if I ran vacuum lines from the manifold tapping to the distributor and the control pressure regulator directly, bypassing the thermal control valve. Would it really be bad to have vacuum advance at idle? My old VW doesn't have anything preventing vacuum from acting on the distributor based on engine temp and it runs fine. Your thoughts?

Thanks in advance and I look forward to learning and sharing more!

Tom

[dmc6960]

Having vacuum to your CPR when the engine is hot would not be the best thing. Will cause the engine to go really rich (too rich) every time you accelerate.

Vacuum advance at idle does negatively affect the idle. However the thermal control valve doesn't have a direct say in that. There is a fully accessible vacuum solenoid which cuts off the vacuum at idle.

Cold engine > No vacuum advance > Vacuum to CPR
Hot engine > vacuum advance above idle > NO vacuum to CPR.

You may just have to bit the bullet and go down into the valley.

[DMCMW Dave]

In short - sure you can do it if you don't mind the car running like crap.

BTW - if the intake has not been off in a long enough time that the hoses have cracked, you should be removing it anyway and cleaning out the valley (see about 80 other threads on that one).

[VIN1498]

Thanks for the quick replies!

It is a tight fit reaching into the valley from behind but I think I can get my hand in there enough to hook up the hoses again. To get the pieces of the hoses that broke off on the nipples I used a coat hanger, bending the end like a small fish hook and sharpened it on the bench grinder. I was then able to snag into the rubber bits and pull them off. The nipples on the thermal control valve on my car are pointing instead of forward (which would be much easier to work with). If it only affected emissions I would not care but if it is going to run like crap then I definitely want to hook it up right. They really could have put that in a better place.
I was able to get a wet dry vac into the valley and sucked out all the leaves and acorns that had gotten in there over the years. I think a chipmunk might have had a nest in there at some point!
I am going to go and pull the intake manifold at some point to clean and refurbish everything in there. I want to get the exhaust system from Specialty Auto on there and that would be a good time to do that, as well as pull the valve covers, set the valves, replace the distributor and rotor, plug wires etc. That exhaust sounds great, is tons cheaper then the others I've read about here and would get rid of the exhaust tick I've been listening too for far too long.