Old as Dirt!
Join Date: Nov 2008
Location: Tampa Bay Area
Thanked 132 Times in 125 Posts
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Perkins 4-108 Radiator Cap
I frequently see posts concerning coolant leakage from the cooling system on Perkins 4-108 engines. For a while we had a similar problem that appeared to be at the fill cap on the heat exchanger but we couldn't tell whether it was from the cap itself, from the tubing connecting the expansion tank to the fill throat or just where. I didn't think it could be from the fill cap as ours was a Perkins original equipment item purchased only a few years ago from TransAtlantic Diesel (for nearly $50.00!!!). Every effort to track down the source of the leakage proved unsuccessful until a friend indicated he's had similar problems and "solved" it with a filler Cap from the local NAPA auto parts store. Considering the relative newness of the Perkins cap, I couldn't imagine that could be the source but, for the sake of the exercise...
The replacement cap, that "solved" our leakage problem is a NAPA Radiator Cap (10 PSI), Part Number 703-1708, at a cost of $5.49 plus tax.
An inspection of the rubber gasket on the NAPA cap shows that it is at least twice as thick as that on the Perkins cap and rather more pliable which was evidently all that was needed to resolve our difficulty. Because of the low cost, I picked up a spare for our stores locker, just in case the problem recurs as the cap ages in use (although I don't expect that).
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