Hi all - I have a 99 LHS with the 3.5 HO engine. My problem is little or no heat coming from the ducts. The only warmth I can get out of it is when I set it on automatic - there is warm air coming from the passenger side floor duct. It appears to be full of coolant, I topped it off but it only took about a quart and a half. The lower radiator hose feels as though there hasn't been any coolant flowing through it, cold. That is if I have the correct hose - down about 10 to 12 inches on the driver side of the radiator.

In the old days before so much electronics were here, the lower radiator hose being cold told me the thermostat wasn't operating. Does this sound correct ? Is the large black cover on this engine just a cover ? Or is it part of the intake ? I'm plenty capable of many repairs, but I don't want to take the intake off. Additionally, the car has been sitting more than being driven for the past couple months.

Thanks for your help.

 

humm feel the hoses going to the firewall snd see if they are cold them self in the back on the driver side. What does the temp guage read? if the rad hoses were cold thee temp guage will show that.

 

I would venture to say that you may have a clogged heater core.

 

The temp gauge is broken into eighths - it's reading 3/8 of the way up, or just under the half way mark. I'm guessing it's the heater core as well, when the heat is on full bore you can feel some warmth near the passenger feet - the closest place to the heater core.

I've been at work this afternoon, didn't have time to check the heater hoses. Plan to do that and some other research in the morning.

I'd rather take a beating than change that heater core, but that's the way it goes sometimes.

 

If u live in the ATL area I am a dash man and had to replace my core in my 99 LH.
Master AC,Electrical and Drivablity I remove dashes for a living.

 

I've noticed that these radiators aren't built to last a long time and the core has smaller than normal narrow passages and build up of silicone and rustand this is what's causing the blockage. This seems to happen easily if your car has been sitting a long time. If there's radiator blockage, then you aren't going to have heat in your cabin. Let me ask you, have you noticed your engine temp gauge running hotter than usual?

My car was severly overheating due to a completely blocked radiator, so my heater wasn't pushing any hot airat all. I ruled everything else out except the radiator, so I removed the radiator and used a pressure washer to clean it out. I can't tell if I completely cleaned it out and if it's flowing sufficiant enough to keep my car from overheating, but it's worth a shot versus replacing the radiator or having someonepretend torod it out. Mostgarage shops will do what I just did and claim that it's been rodded out.

Ive done a lot of research on a productcalled RMI-25. It's the only product out there thatactually claims to dissolves the silicone build up without needing to flush your radiator. Personally, if it's been a few years since your last flush, it's best to flush it out right. To besafe, add the bottle of RMI-25 and and letit run for30 to 40 minutes and then completely flush out the system. It's $20 per bottle. Just do a web search and you'll be able to find it easily. You can't walk into any store any buy it. It's mostly sold in diesel mechanic shops.