Radiator Cap

[MATT]

In the parts cross reference a Napa 703-1422 radiator cap is listed. It is a 10 psi cap and in the PS Mag Article the correct cap is a 6.5-8 psi cap. Could this cap cause some overheating issues or what? This might need to be revised.

Matt

 

[cranetruck]

Should not cause any overheating problem.
The higher pressure increases the boiling point of the coolant.
For about 7 psi the boiling point is about 225F, don't know off hand what it would be for 10psi.
Just watch your engine temp, I have to really work at getting it over 200F so the need for a higher boiling point really isn't there.
The multifuel engine is very efficient.

I'm sure 10psi is okay to use. My cap has no psi marking on it and it was supplied by Memphis. Have been meaning to replace it with a cap with known rating.

 

[MATT]

So what is the danger zone temp of a multi-fuel engine? I have seen few hit about 190 traveling up steep canyon roads, other that that they seem to stay around 160 ish.

 

[cranetruck]

If it hit 220F, I 'd be concerned.
I too noticed how cool the engine was running, especially going downhill as the temp dropped from 170 to 140 or so in a very short time.
The custom radiator was installed (image below), and the temp now actually gets up to 185 or so, which will begin to open the t-stat.
Ideally, the temp should be 180-190 for most efficient operation.

 

[rice]

I would prefer a little cooler than 180 as that isn't too far from the boiling point if you work it hard. I bought a deuce a couple years ago that ran perfect until I started home. The coolant either went bad or someone mixed coolants. It ran up to 210 real quick and push water out the cap., when I let it idle it would drop below 180. I pulled the thermostat and it looked like Jello in the system. I got some radiator cleaner and put in it. Taking 7 hours to go 100 miles. It started getting cleaned out after so many stops to let it cool and add water. The last 20 miles it ran great staying in the 175-180 range. I flushed it after I got home and never had another problem.

 

[JDToumanian]

Every vehicle that I ever raised the cooling system pressure on, has ended up having coolant leaks. Hoses bulge, water pumps, freeze plugs and head gaskets weep, radiators fail. When an engine has spent it's entire life operating at a certain coolant pressure, and then you propose to increase that pressure by 30%, it's asking for trouble.

Just my friendly $0.02 worth of warning... I wouldn't do it, especially when the exact correct replacement radiator cap is available from Saturn Surplus or TNJ Murray for probably about the same price as NAPA's incorrect one.

Regards,
Jon

 

[MATT]

I agree JDT, the Parts Cross Reference should be revised. I will look at Napa for the correct cap and post a new number.

 

[Dieselsmoke]

The cap I got from Murray was a NAPA one.

 

[MATT]

Diesel Smoke, Do you know the psi rating or part #

 

[JDToumanian]

The cap I got from Murray was a NAPA one.

Hmmm... Well, if it's the 10psi cap I personally wouldn't use it. Another possible source is "Frank's Surplus" or "KCGonzo", both eBay sellers that usually have them listed.

Regards,
Jon

 

[Dieselsmoke]

Matt, I sure don't. They went on a deuce I had about 2 years ago so they are long gone now. I've been getting the real GI ones from John Bircheff at the local shows latley.