Guarantor - using a car as security

Guarantor

I wonder if you could help?

I normally ask for a guarantor to be a homeowner and to sign the unlimited guarantee. This does focus the mind somewhat and i've always been able to reclaim lost rent, damages etc.

Currently though, i'm finding it difficult to find tenants who have a home owning guarantor. I'm wondering if i can accept a guarantor but with something explicit in the deed about their car being security? sort of like a log book loan i guess or "your car may be at risk if payments are not kept up", that kind of thing. Any ideas how (or if i can) i'd do this?

Mark