Q: Bubbling behind dashboard when starting car

Recently my car had quite a bad radiator leak which I had to add water to it every morning until I found a product called K Seal which worked ok for about a month then one day there was minor steam coming from the hood after a short run. After I turned the car off I popped up the hood and there was a minor to moderate mess of coolant spray. So the next morning I topped up the radiator with water and slowly drove to my local garage to get fixed. It was a repair not replacement then I was on my way thinking everything would be ok. The next morning I checked radiator reservoir and it seemed ok but on start up there was a gurgling sound coming from behind the dashboard which lasted a few seconds. The following day I checked the radiator reservoir but it seemed a bit low so I re-called the mechanic and took it back. Turns out he forgot to put a hose clamp back on. He fixed it and again I was on my way. It's been about two weeks now and no leak thank goodness however it's still gurgling on start up? My car is a 1987 Honda Prelude 2.0 si 4WS ALB however looks like 1988 model. My car runs well, no smoke. The temperature gauge never goes past half way.

My car has 318000 miles.
My car has a manual transmission.